# mercury 2 stroke outboard oil mixture question



## scoobeb (Feb 15, 2016)

I just picked up a beautiful 93 20hp 2stroke merc that runs on a 50:1 oil mixture and i was wondering if anyone has ever ran the amsoil or any full synthetic oil at say 75 or 100:1 in a 2stroke outboard besides yamaha to run a bit cleaner.I know amsoil makes a 100:1 oil that claims you can run in any 50:1 2stroke and will run perfectly,safely and much cleaner/less carbon build up with no ill effects.I'm in no way saying i'm doing this or i will do it i just was wondering for so many yrs how a yamaha 2stroke can run safely on a 100:1 mix but no other 2stroke can.Is the yamaha built with different parts or specs? This is just a curious question.Also i know tons of people who run a 100:1 mix in their yamaha and it has lasted forever but i know some people say never to run anything less than a 50:1.I know the whole story about why they changed it yrs ago with johnson and all that good stuff but i have always been curious as to why with todays full synthetic tcw3 oil as good as it lubricates can't it be done since oil has come a long way.So my question is i guess is there anyone running a bit leaner then advertised to keep the carbon down?

Also this is not meant to begin an oil war, i just want to know if anyone has or is doing this with great results/less carbon build up and no ill effects.


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## turbotodd (Feb 15, 2016)

the oil still has to go through the combustion process, so it still ends up in the same places....have seen many motors, some of the owners all said that they ran synthetic religiously. I could tell no difference in the exhaust ports, tuner, or leg, they looked the same as the motors that used $2/quart oil.

pappy might be able to shed a little more light on it, as he's seen a lot more 2 stroke motors than I have, and a ton more merc's and Johnny's than I ever thought about.


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## Pappy (Feb 16, 2016)

This could be a really long answer but I will try and keep it short. 
Amsoil is not a certified oil. Never has been and never will be. They have a great marketing dept. but read the fine print about what it would take to make a warranty claim against them for a failure and you will have one of those "Aha" moments. 
Running 100:1 ratios is not new. Johnson/Evinrude Marketing dept. pushed it and did it back around 1985. What was found is that during periods of non-running there wasn't enough of a film of protection on the ferrous surfaces to keep the engine protected. They wisely went back to a 50:1 mixture. We also tried full synthetics in the European race engines and found that during off-season the synthetics would not stay on the cylinder walls. The engines were all stuck and had to be dis-assembled prior to the next racing season. 
The Yamaha is not made of any exotic materials compared to Johnson/Evinrude/Mercury and the rest of the players. They still have steel rods, crank, cast cylinders, steel bearings, etc. All of which will be subject to rust and corrosion depending on the level of protection you choose to leave on them. The simple cycling of cold to hot produces moisture on a daily basis inside an engine. 
Secondly, and most important. In order to run a lean oil ratio everything must remain in perfect working order. Think about this for a minute. A perfect engine. No stuck rings or glazed cylinder walls or a myriad of other normal wear issues. At a 100:1 ratio there will be almost zero protection of a piston should you hit an ice bag (or whatever scenario you choose) and overheat your engine compared to running a richer ratio. Slight restriction in a high speed jet or poor fuel?....same scenario. Heavy price to pay. This is the part that I could go on and on about what the inside of an engine looks like with normal wear vs ........... 
Every manufacturer, in the Owners Manual, specified running extra oil in a racing situation. What is a racing situation? Running at WOT for a 3-lap race or a Marathon. Equivalent to you running a few minutes at WOT except you are not turning left and don't have a number on the side of your boat. 
Outboards don't contribute much as far as pollution goes. At the peak of boating (around 1980) it was calculated that off-road engines in total burned less than 1/10 of 1% of all gasoline burned in the US. Outboard engines are just a small part of that segment.


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## scoobeb (Feb 16, 2016)

I totally understand what your saying.So say if you split the difference and ran a 75:1 which is much more lubrication then 100:1,do you still think your playing with fire that way or would there be enough protection?Also do you in your opinion think that full synthetic 2stroke oil is superior to reg oil.I know that reg oil does the job just fine including the $12 walmart oil but is their any advantage to it of is it just sucking money out of our wallets?I run a ton of wot so i don't know if that would come into play with your opinion.I only idle out of the channel and in no wake zones,the rest is wot,pedal to the metal,lol.


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## Stumpalump (Feb 16, 2016)

I bought a water cooled Montesa 315R trials bike from a guy that ran the Amsoil at 100:1. I took it straight to Moab Utah. On its first long trail ride up a mountain it had a chance to get the pipe and everthing warmed up real good. Once the temp came up and the built up Amsoil started to burn. It looked like the whole mountain was on fire. That thing belched smoke like a freight train for 1/2 hour. It was so bad we were worried about somebody in the distance calling the fire department. Best we could explain was that Amsoil did not burn well and coated everything including the pipe with oil. Once it started to burn it would not stop. It was fine after that and I switched to castor oil. My other experience was with with Royal purple. I was researching oil and got a hold of their oil lab. They would not certify their oil like Pappy referred to either. Why not? Everybody else does ensuring they at least meet some type of standard. Stick with oil from companies that care enough to prove it's doing what it's supposed to do by certifying it.


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## Pappy (Feb 16, 2016)

Sounds like you need to go back and re-read my earlier post. Both of your questions were covered in there. 
Based on what you are telling me I would run a minimum of 50:1 in that engine. I would not spend the extra money on synthetic, just buy a good quality oil. 
Oil's cheap......powerheads aren't!


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## Stumpalump (Feb 17, 2016)

He will be fine as long as he stops every 20 minutes and shakes the gas can. Outboard synthetics do not stay suspended in the fuel. Put the stuff in the bottom of a clear jug and see how hard you have to shake it just to mix it. Let it sit overnight and it will be back on the bottom. The modern outboard synthetics are sold to be injected not mixed. For those that use it then shake it. Read the bottles and pick the ones that say for use in premix applications. I did not read that anywhere on the last bottle of synthetic outboard lube I looked at and for good reason.


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## SumDumGuy (Feb 17, 2016)

Pappy said:


> .... <<snip>>....
> Oil's cheap......powerheads aren't!



Straight-up, that is for sure!



Never understood the desire to run lean on oil. Can't get that purdy smell if you do that. :LOL2:


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## scoobeb (Feb 18, 2016)

I have used 100% full synthetic pennzoil for many yrs with no issues.It is for premix or direct injection as states on the bottle and certified.As far as certified i can't answer that question but i do know that millions of people use amsoil and royal purple and have great success with it including me.I just think synthetic runs cleaner that's why i use it and lubricates better.That is imo.It may be over priced and over rated but it makes me feel better to use it i guess.I will continue to run a 50:1 mix because it's better to run a hair rich then a hair lean.


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## scoobeb (Feb 18, 2016)

2 quick questions to,i just replaced the plugs on the outboard and ran it at idle for like 10 minutes.How long would it take to for the plugs to show whether i'm running to lean or rich because the plugs were still silver and clean after only 10 mins of idle time.I have not run it on a boat yet or anything just at idle with the new plugs.I do know when reved up it sounds good and runs good,smokes like it should and has some black carbon goo coming from the prop which i know is oil and fuel that is unburned.It has not been ran for a long while and needs a good running to clean it out.I did a decarb on it already.The compression is perfect on both cylinders and it seems to run great,idles great so i would think it's running right.Any thoughts on this.

2nd when it runs at idle it runs really cool to the touch,in other words the power head is not hot at all,the water pees great and is cool to the touch,is this normal also for this outboard?It is cool out here in fl still so i figured that was it.May take a while to warm up.The stream never gets hot at all in idle.The power head like i said is extremely cool to the touch.Any thoughts on this?

Any help,thanks.


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## Pappy (Feb 18, 2016)

The overboard indicator is not the best for judging temperature of an engine. 
Any engine that is thermostatically controlled should run at that designed temperature at idle. You may have debris blocking the vernatherm from fully seating. Just a guess. 
You will drive yourself crazy looking at two stroke plugs and trying to determine whether the engine is running rich or lean by them. You are running at several different RPMs and running on totally different circuits in the carburetor. Some circuits will run richer than others. 
Your best indicator you have already answered yourself. The idle quality seems good to you and the overall running quality follows suit. If the engine was running overly rich it would be running rough. Lean it would be surging a bit....just before it stuck.


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## scoobeb (Feb 19, 2016)

I guess I can say once the outboard ran for a few minutes it was like a bit less than luke warm at idle. I guess it may be running a hair on the rich side due to the black carbon flowing out of the propeller. Better to be running a hair rich than lean. The water pump works awesome. I'm wondering if I should fully seat the fuel/air mixture screw and reset the lean/rich setting perfect. I believe once seated it's 1 1/4 turns out then find a happy medium. I have the shop book for it,I do my own work by learning myself,I will never pay the crazy money a marina wants for simple stuff I can fix myself.

It seems to run good,all 2 strokes run a little rough but it idles well and I can rev it up without a hiccup and it seems smooth. I'm doing a bunch of work to it,after I do it all I will see how it runs after I'm done.


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## scoobeb (Feb 19, 2016)

One thing I know for sure,it hasn't been run in a long while so it needs a good run. Needs to be run in hard for a while to clean it out.


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## Ictalurus (Feb 19, 2016)

scoobeb said:


> I guess I can say once the outboard ran for a few minutes it was like a bit less than luke warm at idle. I guess it may be running a hair on the rich side due to the black carbon flowing out of the propeller. Better to be running a hair rich than lean. The water pump works awesome. I'm wondering if I should fully seat the fuel/air mixture screw and reset the lean/rich setting perfect. I believe once seated it's 1 1/4 turns out then find a happy medium. I have the shop book for it,I do my own work by learning myself,I will never pay the crazy money a marina wants for simple stuff I can fix myself.
> 
> It seems to run good,all 2 strokes run a little rough but it idles well and I can rev it up without a hiccup and it seems smooth. I'm doing a bunch of work to it,after I do it all I will see how it runs after I'm done.



Since everything seems to be running well w/ this motor, I think you should change out and adjust everything you can until it's just perfect!

:LOL2: :LOL2: :LOL2:


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## scoobeb (Feb 19, 2016)

I lightly seated the screw on the carb and backed it out to 1 1/4 turns,then i went cw in till it ran like crap which was at one turn out from lightly seated,marked it,then i went cc to near 2 full turns out from lightly seated and it started to run like crap,marked that.Then i went in the middle which was at 1 1/2 turns out from lightly seated which ran best and like a freaken sewing machine,i did push it just a hair past 1 1/2 turns to make it i mean just slighly, i mean ever so slighly on the richer side to be safe,Man i couldn't be happier i tell you by the way it runs.I of course did it in a tub in f gear and not in idle.I revved it up in n and in f gear and it was as smooth as silk,not a hiccup or hesitation to speak of.The big test will come in the water when i open it up.

I also took off the lower unit and it seems like the whole thing was recently replaced but i will take it all apart to make sure,may as well while i got it off.Man the lower unit is so simple to take off.I will post pics of it when it's completely cleaned up and all the work is done.


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## scoobeb (May 7, 2016)

I just wanted to update my engine,I replaced everything except the power head and lower unit gears basically. I did new,coils,wires from coils to plugs,new plugs,I replaced even the bolts holding the coils in as well as the shell that goes over the coils. I replaced lower unit oil and gaskets and drain plugs,replaced all the gas lines and new line from thermostat to the pee hole,new thermostat and gasket by the way was my issue of it not warming up,someone just stuck the shell of the Stat in with the gasket but completely removed the whole Stat so it was never warming up and always running cold. I replaced a complete new fuel filter assembly as in hoses and all,replaced the male gas intake on the engine as well,replaced a complete water pump kit,everything, impeller, gaskets,washers, key,housing,intake tube,It's all brand new,rebuilt the entire carb,new gaskets, needle,everything but the float which was good. Set the fuel air mixture screw to factory specs. New pull cord .

I de greased the entire engine I mean spotless, what fun that was,then I re greased all the fittings and anything that moves,lol. New 6 gallon tank and line, 7 bottles of full synthetic tcw 3 oil,greased the prop and spline. I think that covers most of it,runs like a sewing machine now.This will be in my possession until i either die or decide it just eats to much gas and i'm ready to go to a 4stroke. I just can't see myself getting rid of it,it is by far one of the cleanest 20/25hp 2stroke outboards on the planet unless you pull one right out of the box,compression is 100% perfect also.I had a close friend offer me a large amount of money for it and turned it down without hesitation so that will tell you what i think of this outboard.It sat for a very long time so to me it was worth putting a hair over $200 into when now i know everything as far as maintenance is taken care of for yrs now except like the lower unit oil change every 6 months or so.All i can do is hope it lasts for a very long time which i believe it will.

Here are pics of it all done and greased up. The only other plan I have for it is to sand everything above the decals and fill in any gashes with epoxy paste and then repaint it nice. The rest of the engine looks new,let me know what u think for a near 24yr old engine,imo,i think it can't get much nicer then this and i have let alot of really nice engines slip through my fingers and have extremely regretted it to the core of my soul,this time i won't make that same mistake.This motor in amazement has the power of a 25hp even know it's a 20,i cannot believe how much power this little motor has.I am going to the lake next week and this time i'm grabbing my gps because i forgot it last time and i will post how it does on a brand new 1648 flat botton jon boat with me and with 2 in it,thanks.


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## Pappy (May 7, 2016)

You did a fantastic job on that engine!


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## JMichael (May 7, 2016)

The motor looks like new, but if you asked a question about oil mixture "per title", I missed it in there. LoL As far as I can tell, there's only one problem with that motor from my perspective, the shifter is built in to the throttle grip. I've owned one merc that had that feature and I did not like it. But that's just a personal preference thing. :mrgreen: Nice job of cleaning her up and putting it back in to service.


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## JL8Jeff (May 7, 2016)

That engine looks nice and clean. I think a lot of the Mercury's idle air adjustment is around 1-1/2 turns even though some of the books may say 1-1/4. That extra 1/4 turn made a big difference on a 90 hp that had a lean "sneeze". On a side note, I've been running the synthetic premixed at 80:1 to 100:1 in several engines for the past 8-10 years with no issues so far. But I don't run around at WOT (I usually find the quietest/smoothest cruising speed) so that may make a difference. And I usually run the boat a couple times a week during the season as well.


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## turbotodd (May 7, 2016)

One thing worth mentioning is carburetor jetting. I've seen a few 2 cycle engines destroyed due to the owner running 50:1 mix when it was designed from the get-go to run 100:1. Reason being, the oil/fuel mix goes through the jet. When you double the amount of oil, some fuel is displaced, the engine's air/fuel mix runs lean. If the fuel is questionable quality from the get-go, and this happens...under load full throttle full RPM, etc, yes it can burn a piston. I actually did it on my scooter, was originally oil injected (autolube), I ditched the injector and hose and premixed it. Noticed right away that I would have to re-jet. Thought it was odd, turned around (about 4 miles from home), started back and before I turned onto the street I live on, the engine started losing power. Just died. Pulled head, piston burned on the exhaust side, smoked it, the ring, and the plated cylinder. First time I've actually experienced it, even though I'd heard of it before I called it a bunch of trashtalk. Apparently I should've listened.

If it says run 50:1, run it at 50:1. Especially on the Mercasil engines.

Agree with previous post about not liking the shift in the throttle grip. I hated it, but again personal preference....lots of guys love it for one-handed use such as running lines or duck hunting or whatever.


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## scoobeb (May 8, 2016)

Pappy said:


> You did a fantastic job on that engine!


Thank you,means a lot to me.I busted my hump cleaning it i mean for many man hrs.I took off the 20hp plate under the lower cowl and to my surprise there was what's called mud daubers we call them here in fl.They take mud and build nests with it,they look like wasps but are harmless.There was quite a bit caked up under the plate but it wasn't harming anything thank God.When i say i cleaned it i mean i cleaned every milk and cranny,crevice i could reach to clean,every hole,everything i could get to.I cleaned i can't tell you how much old grease off this thing,wow.I used dawn soap to clean the whole outboard.I used a whole huge bottle in a spray bottle.It was worth every minute.

As far as the all in one shifter,i love it and think that is what makes the mercs special. that is the best feature to me.I have never once had any issues.This engine shifts like butter,i mean really silky smooth,no grinding or any force needed like the new 20hp 4stroke merc i had,that takes some force to shift, but it wasn't broke in one bit yet to be fair.


As far as the fuel air mixture it was around 1 1/2 turns out from seated and i notched it back i mean a tiny hair towards the rich side to be safe and it runs like a sewing machine.It is a 50:1 engine and that is what i'm going to run because since i'm using full synthetic on it i'm hoping it will run cleaner but i won't skimp out on the oil especially after all the work i did to it.I also use lucus stabilizer in my non ethanol gas and ring free.When i started taking off the original stuff it all like just crumbled to pieces,especially the coils,they just fell apart.All the wires were corroded and need to be replaced,Plus they were the wrong length wires and wrong coils so i made sure everything on this is as perfect as it can get.I'm very anal when it comes to maintenance and making sure everything is up to par.I believe in doing it right the first time.


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## scoobeb (May 8, 2016)

Thank you guys for all the kind comments,means a lot to me as i told pappy.I think i will keep this outboard for a long time maybe even permanently.The way i take care of my engines it will look like this even another 15-20yrs down the road.One of the greatest things i have learned about this engine from the older guy i bought it from was the prop is actually the original which is amazing to me.The prop is 24yrs old,wow.


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## scoobeb (May 9, 2016)

Jlbjeff,your merc runs 50:1 doesn't it? You run at 80:1 with it though and have never had any issues? I've always wondered why only Yamaha pushes 100:1 but every other brand outboard runs 50:1. I believe any 2 stroke can run at least 75:1 to run a hair cleaner but I will still run 50:1 no matter what. I may run it a hair leaner but not to much.


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## JL8Jeff (May 9, 2016)

scoobeb said:


> Jlbjeff,your merc runs 50:1 doesn't it? You run at 80:1 with it though and have never had any issues? I've always wondered why only Yamaha pushes 100:1 but every other brand outboard runs 50:1. I believe any 2 stroke can run at least 75:1 to run a hair cleaner but I will still run 50:1 no matter what. I may run it a hair leaner but not to much.



My oil injection pump was bad when I got the motor (1994 60/45 jet) so I've been premixing. I ran 80:1 to 100:1 in my old 1999 Johnson 40 as well. Remember, the 50:1 mix is the ratio needed for WOT. The oil injection or VRO mixes closer to 100:1 at lower speeds. I don't blast around at WOT and I usually only run for 10-15 minutes at a time so I don't have an issue with the 80:1 mix. If you're going to need to run close to WOT for any amount of time then the 50:1 is a much safer mix. It really depends on the overall combination of the conditions, location, boat/passenger weight, running time.


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## Pappy (May 10, 2016)

As far as an engine running lean on a heavy oil ratio? Pure bunk. 
If manufacturers recommend doubling the oil for any racing situation on a bone stock carbureted engine then that engine is run at WOT for whatever period necessary for the event. 
At WOT the engine has to get rid of a massive amount of heat. Do you think a manufacturer would recommend this if they even thought that a richer oil mix would lean out the engine? That is a boat ramp myth.
All manufacturers that used carburetors set the high speed jets on the rich side of optimum just for safety sake and a reduction of warranty claims.
Want to know what is currently leaning your engine anyway? Ethanol fuel. 
10% ethanol mix in gasoline leans the average mixture 6%. Do the math! Has not made a dent in failures. 
In short.........oil is cheap and powerheads are not. Additional oil can and will protect your engine better should you get debris in your carbs or an overheat.


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## JL8Jeff (May 10, 2016)

I think he was referring to running lean as in a lean oil/gas ratio, not a lean fuel/air ratio (at least that's how I was reading it). With a smaller motor, I would think there is more of a need to run a higher rpm so the stock oil mixture is a safer way to run.


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## Sinkingfast (May 10, 2016)

I think Turbo was referring to the massive #-o increase in viscosity by the added oil, causing a lean on fuel condition. If the motor is affected by running say 32-1 over 50-1, that motor was lean to start with. 

Just run 4 0unces per gallon of dino 2stroke oil. Better chance of having it 20 years from now.


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## Pappy (May 10, 2016)

Again, not correct on either count. 
When we jet for racing we lean the hell out of the engines in the fuel department. We then double the oil. The reasoning for this is that the oil will help cool the pistons and also provide a ton more protection against sticking a piston due to the lean condition and fluctuations in cooling water volume and pressure. Production engines both small and large are pig rich compared to what you can run. 
In a production situation the main reason for running additional oil is to protect the engine when things go South. Overheats and dirty carb circuits being the two main culprits. A production ratio of 100:1 doesn't have a prayer of protecting an engine running hard and catching an ice bag over the water inlets. The pistons are running at their hottest (most expanded) and the block is or was running at its coldest. The piston grows beyond its designed in tolerances immediately and it's metal to metal on the exhaust side of the piston to the cylinder wall. The only thing that has a prayer of helping is lubrication. If you are not quick in identifying the issue then the piston gets pushed over to the intake side and locks up. Once it locks there is a good chance it will put a rod through the side of the block.
Like I said in an earlier post, oil is cheap and powerheads are not. I make an easy choice and run additional oil.


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## scoobeb (May 11, 2016)

Well i got one thing going for me,i don't use ethanol fuel, i use nothing but ethanol free fuel in my boat engines.


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## Pappy (May 11, 2016)

Same here Scoobeb! One less hassle.


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## JMichael (May 11, 2016)

scoobeb said:


> Well i got one thing going for me,i don't use ethanol fuel, i use nothing but ethanol free fuel in my boat engines.



I try to but this year it's going to have added challenges to do so. Up until a few months ago, I had 2 sources for eth free fuel within 25 miles. One sold out to another company and the new owner is not going to supply the fuel any longer and the other just closed their doors and went out of business.


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## scoobeb (May 12, 2016)

If you use your outboard allot you will have minimal issues if any,let it sit with ethanol fuel,forget it. I use ring free and Lucas stabilizer,the green bottle in Walmart for all my gas and never once had any issues even sitting for months. Good stuff. I also do a de carb once every 6 months on my outboard, 3/4 gallon of gas,1 can of seafoam,works awesome.


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## scoobeb (May 12, 2016)

I didn't want to start a whole new thread but what would be symptoms of bad timing on my merc. I have been reading allot and it says don't ever mess with the timing if the engine runs good,but I want to learn what I would be looking or hearing for if the timing was off. Thanks for any help.


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## Pappy (May 12, 2016)

Short version......If the timing were low you would not reach your normal RPM. If it were high you may be replacing a piston depending on how high and other factors.


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## WaterWaif (May 12, 2016)

scoobeb said:


> I just wanted to update my engine,I replaced everything except the power head and lower unit gears basically. I did new,coils,wires from coils to plugs,new plugs,I replaced even the bolts holding the coils in as well as the shell that goes over the coils. I replaced lower unit oil and gaskets and drain plugs,replaced all the gas lines and new line from thermostat to the pee hole,new thermostat and gasket by the way was my issue of it not warming up,someone just stuck the shell of the Stat in with the gasket but completely removed the whole Stat so it was never warming up and always running cold. I replaced a complete new fuel filter assembly as in hoses and all,replaced the male gas intake on the engine as well,replaced a complete water pump kit,everything, impeller, gaskets,washers, key,housing,intake tube,It's all brand new,rebuilt the entire carb,new gaskets, needle,everything but the float which was good. Set the fuel air mixture screw to factory specs. New pull cord .
> 
> I de greased the entire engine I mean spotless, what fun that was,then I re greased all the fittings and anything that moves,lol. New 6 gallon tank and line, 7 bottles of full synthetic tcw 3 oil,greased the prop and spline. I think that covers most of it,runs like a sewing machine now.This will be in my possession until i either die or decide it just eats to much gas and i'm ready to go to a 4stroke. I just can't see myself getting rid of it,it is by far one of the cleanest 20/25hp 2stroke outboards on the planet unless you pull one right out of the box,compression is 100% perfect also.I had a close friend offer me a large amount of money for it and turned it down without hesitation so that will tell you what i think of this outboard.It sat for a very long time so to me it was worth putting a hair over $200 into when now i know everything as far as maintenance is taken care of for yrs now except like the lower unit oil change every 6 months or so.All i can do is hope it lasts for a very long time which i believe it will.
> 
> Here are pics of it all done and greased up. The only other plan I have for it is to sand everything above the decals and fill in any gashes with epoxy paste and then repaint it nice. The rest of the engine looks new,let me know what u think for a near 24yr old engine,imo,i think it can't get much nicer then this and i have let alot of really nice engines slip through my fingers and have extremely regretted it to the core of my soul,this time i won't make that same mistake.This motor in amazement has the power of a 25hp even know it's a 20,i cannot believe how much power this little motor has.I am going to the lake next week and this time i'm grabbing my gps because i forgot it last time and i will post how it does on a brand new 1648 flat botton jon boat with me and with 2 in it,thanks.



Reads great!Nice.

We should take wild guesses on GPS results?
I'd guess upper twenties on calm seas and medium weight/ build rider.
Mid twenties for two.
O.K. ...25 avg. :---)


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## scoobeb (May 13, 2016)

Pappy said:


> Short version......If the timing were low you would not reach your normal RPM. If it were high you may be replacing a piston depending on how high and other factors.


Well I'm going to GPS my wot speed soon. I know from experience with these outboards as far as speed with just me on a 1648 jon boat I should hit between 26-29mph. If I'm in the teens or very low 20s like 20-23mph I know something is not right but from the feel of it she hauls a$$. I have watched over 300 videos on YouTube on this outboard and no one was below 26mph even with a full load. I do know these mercury's have so much power,I've had great luck with them,the compression on both is dead even at 125lbs so that is good. I will post GPS results In the next few days.


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## scoobeb (May 15, 2016)

I will soon gps my speed and post


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## scoobeb (May 15, 2016)

I may need to raise the motor a hair for optimal speed.


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## scoobeb (May 22, 2016)

As I thought, the motor is a complete powerhouse. Wot with near 1000lbs total weight I hit 28.3mph which is insanely impressive for just a 20hp. This by far one of the most powerful Engines I have ever used. I smoked my buddy's 20hp 4stroke Tohatsu in the long run,off the line he got me because he was using a 10 pitch prop and mine was 3 sizes bigger at 13,we both were running identical boats,1648 alumacraft flat bottoms so it was a fair run. He had much less weight of around 700lbs total weight, he got us off the line but I caught him and passed him in a matter of seconds. I was seriously highly impressed with the power and torque of his 20hp 4stroke Tohatsu, it just amazed me. They are getting these 4strokes better and better every yr as far as trying to get near the power of a 2 stroke. After seeing how his Tohatsu performed I wouldn't hesitate one second to run one on my Jon boat.


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## turbotodd (May 23, 2016)

All (well a lot of them) of the old <40hp Yamaha outboards were 100:1, they were designed to run 100:1. Of the thousands that we sold when I worked there, nary a single powerhead failure. Lots of water pumps, and questionable pumps that owners would say "well it works" (but it was just a real weak pee stream), and they never died, though, in a few weeks those guys were usually back needing impellers, cups, etc. I take that back, I think I put 2 powerheads on 25hp twin carb motors, because the owners had hit submerged objects HARD and repeatedly (flooded timber) which twisted the crank and took out the labyrinth seal. Yamaha picked up the tab on one, the other insurance claim. I remember both quite well.

Take a 100:1 motor (specifically the 25hp twin carb) and run it at 50:1 and I can tell a huge difference in run quality. Top speed, no difference. Idle and mid range, night and day. Most owners won't notice it. Usually had to richen up the idle mixture on those motors whose owners were hard headed to the point where they were going to run 50:1 no matter what was recommended. About a 1/2 turn on the screws, then up the igntion lead from 7ATDC to 3-4 ATDC, and they'd purr like a kitten. Leave them alone and they'd sneeze fiercely until they were hot (not warm, hot). This was common on all of them, even brand new ones running 50:1 break-in mixture-as recommended by Yamaha. These were not racing engines, racing engines could care less about idle quality, oil usage, fuel usage, smoke, or anything else but making the most power and speed. Exactly like a lot of duck hunters in this area, they could care less about idling...all they want is to have the fastest "25 hp" motor regardless of whether it'll go into gear without crunching or if it'll even idle below 1500 RPM at all. wide open down the narrowest canals, 2-3-4-5 boats wide beating and banging each other at 50+ mph. I did it a couple times and I was not impressed. It's not fun.


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