# 15 4stroke vs 15hp 2stroke



## scoobeb

I have a brand new 15hp 2stroke yamaha on a nice 14ft jon boat.It scoots pretty good.I was just wondering if i were to get a brand new 15hp 4stroke would i see a drop off in performance?I now the 4stroke is about 35lbs heavier.I'm looking at a new merc/tohatsu 15hp 4stroke.I know the yamaha is new but i think it may be time to catch up to the times.I will have no problem selling the yamaha if needed to.

The thing i want to know if i were to go with the merc,since they fixed the gear ratio in them to a 2.15 it should give it close to the same power as the 15(as far as out of the hole).My biggest thing is would i loose anything going from a 15hp 2stroke to a 15hp 4stroke besides the fact it's a lighter motor then the 4stroke.I like the idea of no mixing oil and it runs cleaner,may even get a few extra miles on a tank of gas.

Has anyone done this,go from a 2stroke to 4stroke of the same size(15hp)What was the difference?also was it worth doing?I always wanted to own a 4stroke.I may just keep the 2stroke,haven't really decided yet.But if i go 4stroke i see no need to keep both.Any help on this would be great,thanks.


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## V8_TITAN

if you have the money then why not ? I would have a 4 stroke on mine if I had the money. and I would go with a mercury, they seam to be doing something right. yamahas are too heavy and ive heard that they are more money in parts. 

The whole no oil mixing thing is great but remember, you will have to change your oil frequently and oil filter. not sure but probably having a timing belt/ chain to worry about now also. 

as far as mpg, I would bet there would be a noticeable difference in fuel consumption.

I havent seen any smaller 4 strokes run yet, but I was on a boat with a 250 suzuki 4 stroke and you can hardly even tell when its on and idling. 

so if it were up to me, I would deff have a 4 stroke on my boat. If I already had a newer yamaha 15 2 stroke, I would probably keep it until its just old enough to get top dollar for it, and then go for a newer 4 stroke.


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## DanMC

Hi,
One thing i would never do...get a Mercury... [-o< God help you...a 4 stroke motor by Yamaha or Honda is a piece of mind future wise...and if you would want to keep up with technology....per say...ask yourself one thing :?: ...whatever you drive is a four stroke or a two stroke and then ask yourself why would i get me a "primitive" motor...go with 21 st century =D> not 19th #-o .
Dan


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## TNtroller

gaining 35lbs due to going 4 stroke without an increase in HP would make me think performance is going to suffer to some extent just due to the weight gain. The 4 stroke would be better for extended trolling (no oil in the gas to foul the plugs), they are quieter as I have heard a 60hp 4 stroke idling by and chatted with the owner, did not have to raise our voices at all. Have no opinion on who makes a better motor in the size your looking at.


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## scoobeb

Ok would it be worth upgrading to a 20hp 4stroke instead of the 15hp 4stroke or should i just stay with the 2stroke?


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## LOWEBIGJON

I would keep the 2 stroke..


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## Specknreds

I upgraded to a 4 stroke 25hp Yamaha in '03 from a 2 stroke 25 Yamaha. Very little difference in performance. I lost 1MPH GPS. I did have a few issues with weight but the have made a lot of improvements since '03. I went from about ~35 miles on 6 gallons to way over 60 miles.

I have some serious hours on this little motor with no problems due to the motor. I did have some Ethanol issues before I knew the effects of Ethanol. It's normal for us to 20 miles one way through the marsh on a normal trip. 

The oil changes are around $15 using Yamaha parts. Cheaper if you go aftermarket. I stick to Yamaha parts because they are reasonable on small HP. I also have a 200 HP 4 stroke on my bay boat. It will knock a hole in a 100 dollar bill to change the oil and fuel filters in it using Yamaha parts. I use Castol in it and Sierra filters. I'm avaerage 250 to 200 hours a year on it. This is what the guides and commercial boats use and most have over 2000 hours on their 4 strokes.

I get 3.5 MPG in the bay boat running wide open and have seen it get well over 4 MPG just cruising. A buddy with the same boat only gets ~2.5 MPG with his 2 stroke and spends several $100 on 2 stroke oil every few months. You have to remember these boats see more hours in a week than most see in a year. 

I will NEVER own another 2 stroke.


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## moloch16

My understanding is 2-strokes develop more power than 4-stroke, and Yamaha is a really, really great motor. I'd keep the 2-stroke. (I recently bought a brand new motor and went with a 2-stroke 25HP yammy).


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## scoobeb

Yes yamaha is one of the best outboards out there.Most of the name brands are all just as good anymore though.I just think the 20hp 4stroke would do wonders replacing my 15hp 2stroke.I am going to think about it some more before i make a big mistake.The weight is the big issue i'm thinking about.

I have seen tons of videos on the 20hp 4stroke mec/tohatsu and that motor screams with a ton of power for a 4stroke.It has some great hole shot also from what i could see on the videos.I just want a cleaner,better on gas and the environment outboard.


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## scoobeb

If anyone has anything they could or want to add to this thread by all means please do so.I mean i'm not sure whats going to happen here in the near future with 2strokes also.The u.s may just ban them to use for good who knows what this country will do anymore.That is another thing that makes me nervous,how long will we be able to use carbed premix 2strokes?I'm sure it won't be here asap but i think some time soon they will ban the use of them and then they are a nice boat anchor.

I personally think if i'm going to replace the 15 i need to get the 20hp for that extra punch.From what i know the merc/tohatsu is no dog,they are strong motors from what i have seen.I was hoping some people in here could tell me how there 15 or 20hp 4strokes perform on their jon boats if anyone has them.That would help a great deal for me to have some peace of mind in making my decision. [-o< .I know the top end would be ok,i don't need a speed demon anyway as i'm only n a jon boat.I think i could do at least 20 to 25mph which is plenty fast for a tiller motor.

From what i have seen i'm leaning towards the merc/tohatsu so far if i do this.I like the ratchet tilt that is built into the merc.All you have to do is pull back on the motor and no need to constantly move a pin up and down.That is a huge feature on a heavy outboard.I don't know if the tohatsu is the same.I need to find that out.


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## benjineer

Keep the 2-stroke if you like it unless someone wants to pay you what you bought it for. If you want to help the environment, you've got to sell yours to someone who will use it less than you do, or you could just send it to the scrap yard. Holeshot seems a non-issue when talking about a flat bottom tin. How low does your boat sit when not on plane? It's not quite the same as a heavy glass boat that has to literally get out of the "hole". I think you would like the 20 or 25hp better. I'm running a 25 on a 16ft boat. It planes fast and runs about 24mph, and I'm satisfied. I don't expect them to ever ban 2-stroke pre-mix engines any more than they will ban classic gas-guzzling cars from being driven. I do expect them to raise emission standards on new motors until there are no more premix 2-strokes made. If I had unlimited money to buy new motors for either of my old boats it would be Etec or 4-stroke Yamaha. Both are quiet and fuel-efficient. I'd probably go with Etec because of the hp/wt ratio and no oil changes.


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## scoobeb

I put it on craigslist to test the market,i can actually get more then i paid for it but i will take what i paid.I guess if there is no planing issues with a jon boat then maybe it might be worth the gamble.I can sell my motor for anywhere between $2200 and $2500 easily because of how rare they are.My motor is 100%brand new never been used ever since out of the box.

Then i can turn around and get a brand new 20hp tohatsu for around $2400 out of the box,manual of course which is what i want.On the other hand i can get a brand new 20hp 4stroke merc which is the motor i want for close to $2500 give or take a few bucks.I eally like the ratchet tilt on the merc,it would make a 115lb outboard easy to tilt up and down instead of constantly picking the motor up out of the water and moving the pin up and down.

I'm gonna have to give this some serious thought.Like i said getting my hands on a outboard like this ever again will be impossible so i have to make the right choice.Maybe i will just buy a smaller jon boat (12ft) like i want to anyway and throw the 15hp on it and then just buy a bigger motor for my big jon boat.I have a wide 14ft jon boat now rated for a 25hp.I just think the 15hp is a hair under rated once i get all the weight in the boat.I still know it will plane but not by much as a 25 would make this boat fly.

Thanks for all the posts so far,keep them coming.Good smart people here. :mrgreen:


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## Pappy

You mention you want a manual engine. One thing to think about on a manual 4 stroke is the starting of the engine. A four stroke only hits every other stroke and compression is usually quite high. You have to pull that manual starter rope quite a long ways to get a couple of power strokes out of that engine and with high compression it can be a bear when the engine isnt in as good a tune as when brand new. Occasional water in the fuel or some other random issue can render the guy on the dumb end of the rope pretty helpless after cranking for a while. The two stroke will definitely have more power and acceleration, hands down. Something to think about! I have stayed out of this and read the various posts with interest and got a kick out of some of the mild misinformation of one or two of the answers so far.


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## scoobeb

Hey pappy i know your a smart fellow but the new 4strokes are extremely easy to pull now.They have a decompression device built into them now,you can pull start it with 2 fingers.My yamaha is also easy to pull.Motors are getting easier and easier to pull for the manuals they are not like the older outboards wher they would rip your arm off.Try pull starting a mid 90's 25hp 2stroke johnson,you talk about hard to pull you need 4hands and alot of elbow grease to pull start one of them.

I have pull started over 10 4strokes from a 2.5 to a 20hp and they are simple to start.I just never got to use any of them.I think the 20hp 4stroke merc is a beast from what i have seen.I think it would move my wide 14ft flatbottom like a missle but i want to be sure before i do anything.I'm going to look into it a ton more before i decide to sell it.I will have no problem selling a new 2stroke if i choose to go the 4stroke route.I would like to keep both but my buget won't allow that.Ok anymore info would be just dandy.


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## LonLB

I've never been in a SHO 4stroke, but all other 4 strokes, are just slower. There is no way around it, and in my experience, no debating it.

You may get somewhat similar top end speed, but from idle to top end will be much slower.


And I wouldn't worry about 2 strokes being banned.....Maybe someday, but that will be a LONG ways down the road. If ever. (with the exception of select waters-but that is already true; case in point=electric only lakes)


As for brand, again drawing from my own experience (not what I've heard or read about) the only boat engine I've seen catastrophically fail, was a Yamaha 4 stroke.
Sure I've witnessed other motors fail. But I've also had a 50hp 2 stroke Evinrude apart that still ran OK, but one of the cylinders needed to be sleeved to eliminate the deep scoring....Yet didn't fail entirely.


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## nomowork

I changed from a two stroke to a four stroke. I really like the noticeable difference in noise level. I can run the motor and not have to yell to my GF who sits on the front of the boat! 

In my case, all the new features on the new motor are great!


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## DanMC

It wont be long before all things two stroke (including lawn tools,shavers  ) will be baned. Just te be on the safe side of the "future" get youself a four stroke Honda (Honda makes some of the cleanest burning motors period,it doesn't mater if it is a weed wacker,lawmover,shaver  or an ouboard  ) Honda knows more than a thing or two when comes to engines. Honda afterall is worlds largest engine manufacturer for a reason,and if you are talking four strokes...really nobody knows better four strokes than Honda, that is the reason Honda never made a two (primitive technology  ) stroke motor for anything...at least consider a Yammy...but for the love of God... [-o< 
Dan


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## scoobeb

If i go 4stroke it will be a merc/tohatsu not a yamaha.Yamaha is to over priced.I can get a merc 20hp 4stroke for over $400 less then a yamaha and darn near $1000 cheaper then a honda.If you want to get right down to it the tohatsu is the best outboard hands down for what your getting for the money.I just like the ratchet tilt that merc has and no other outboard has that feature.Honda is way over rated in my opinion.Are they good outboards,of course but the price you pay is insane.All the newer 4stroke outboards are built to last no matter what you buy,i'm talking major brands here also.

The 20hp 4stroke merc/tohatsu has the best power to weight ratio for all the four strokes from what iv'e gathered and from a ton of peoples experiences with their small mercs.I think the merc/tohatsu is the best 20hp 4stroke out there for mainly the features it has.The 20hp 4stroke merc/tohatsu has the best gear ratio(2.15) for the best hole shots,an (awesome ratchet tilt system(merc only) to help out with the weight of the motor for an easy tilt system,all the controls built into the tiller,electric start also has a manual recoil to pull start it unlike the yamaha,plus they are a sharp looking outboard.Built extremely good and built to last forever if taken care of.


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## jasper60103

The 20hp 4stroke merc/tohatsu sounds interesting. I wonder if it would provide decent performance for my tinnie? i.e. Plane easily with two adults, gear and maybe reach 20-25mph? It's 16' long, semi-v, around 400# and I weigh about 200#. I like to remove my motor and store over the winter, and the 25hp or larger 4 strokes weigh too much.


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## LonLB

I know this isn't what you asked jasper, but if I were you I'd forget about it. You just can't beat that motor you have on a boat your size. Those things are light, and ROCK SOLID reliable. In my experience. If I had a boat that size, that is the motor I would put on it.


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## jasper60103

LonLB said:


> I know this isn't what you asked jasper, but if I were you I'd forget about it. You just can't beat that motor you have on a boat your size. Those things are light, and ROCK SOLID reliable. In my experience. If I had a boat that size, that is the motor I would put on it.



I hear yah, LonLB. I was just curious about 4 strokes though. A new boat motor is not on my list of priorities now. Thanks.


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## scoobeb

Yes i would almost bet it would scoot that boat of yours jasper.Go to you tube and punch in 20hp 4stroke merc or tohatsu and a million videos will pop up so you can see the power it has.That is where i'm basing my opinions from.Plus i found a few people here who run 15hp 4strokes,so i would bet a 20hp would be even better.I don't know what speed you will reach but a guy in one of the videos on you tube has one on a extremely heavy wooden boat,cc he planes out extremely fast in the video and hits the mid 20's.

Not to shabby.You can get a brand new 20hp tohatsu from onlineoutboards.com for like $2400.They advertise it at $2550 but you can call to get the price down.That is shipping and tax included.I personally will go with the merc just for the fact the ratchet tilt will save your back from lifting the motor and moving a pin up and down.The merc has 5 tilt positions you put the tilt on what setting you want and if you want to start over you tilt the motor all the way up and then it will come down again so you can re adjust it to where you want.No other motor has that that i have found so far so that would be the deciding factor for me if i go that route.Plus it is a well built machine by tohatsu's plant,same exact powerhead as the 20hp tohatsu.

All the brands like i said seem to be bulletproof,i guess it comes down to features.The merc has an easy oil filter to change,all controls built into the handle,ratchet tilt,the best i have seen lower unit gear ratio,plus they are probally bulletproof if taken care of like any other motor.It all comes down to what features you want and of course the weight,my motor is a 15hp 2stroke yamaha (79lbs)compared to (115lbs) for the merc,big difference.My boat will hold it no problem but that little 79lb motor is hard to beat.I think i will put it up for sale to see if anyone comes to look at it.


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## scoobeb

Jasper i forgot to mention there is a guy on you tube with a short like 15 second clip where he has the same type of boat you have,it's a 1467 v alumacraft and he states he thinks he is hitting close to 30mph.He looks like he's flying,check it out and let me know what you think.


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## jasper60103

scoobeb said:


> Jasper i forgot to mention there is a guy on you tube with a short like 15 second clip where he has the same type of boat you have,it's a 1467 v alumacraft and he states he thinks he is hitting close to 30mph.He looks like he's flying,check it out and let me know what you think.



Yea, I saw that video. That's a pretty light weight setup compared to mine, but the motor pushed it very well...

https://www.youtube.com/watch?v=uFL5vR2F-dE


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## bcbouy

where have you guys been looking that a yamaha is too expensive? have you priced an e-tec lately?i have an 85 evi 9.9 and a 2011 yami 15,both 2 strokes,and the yami is really quiet compared to the evi.


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## scoobeb

Sorry jasper it was a lowe,my fault.basically the same boat as the alumacraft.Check out the 20hp tohatsu that pushes the wooden boat,i think there lady bug boats.The boat was over 350lbs by itself and the tohatsu pushed it in the mid 20's.


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## chavist93

DanMC said:


> It wont be long before all things two stroke (including lawn tools,shavers  ) will be baned. Just te be on the safe side of the "future" get youself a four stroke Honda (Honda makes some of the cleanest burning motors period,it doesn't mater if it is a weed wacker,lawmover,shaver  or an ouboard  ) Honda knows more than a thing or two when comes to engines. Honda afterall is worlds largest engine manufacturer for a reason,and if you are talking four strokes...really nobody knows better four strokes than Honda, *that is the reason Honda never made a two (primitive technology  ) stroke motor for anything*...at least consider a Yammy...but for the love of God... [-o<
> Dan




What is this guy talkin about?? #-o :roll:


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## scoobeb

I'm starting to wonder that myself.Is he just a spammer because he seems to be in a ton of threads with some off the wall stuff.He talks about insurance and all other crazy sorts of stuff #-o


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## scoobeb

Man the more i do research for thie 20hp merc or even the tohatsu it seems like the way to go.The technology is like night and day compared to my 2stroke.Alot of people seem to be scared to buy a 4stroke because of how complex the system is.In other words when or if it breaks down more money and harder to fix.But i have to tell ya from the stuff i'm reading these little mid range motors seem to be bulletproof as long as you take care of them.I'm sure there could be a problem here or there especially with the fuel system,ethanol.

From some other sites i have just visited the word is these little mercs or any of the small 15 to 20hp 4strokes are bad a#$ little motors.I have watched a ton of you tube videos on the performance of different 15 and 20hp 4strokes,like honda,merc,tohatsu and yamaha they all seem to push a flat bottom extremely well even with a few people in a boat.I think what i will do is use my motor for a reasonable amount of time to see if it does what i need it to do.I don't need a speed demon but a motor that will hit the lower to mid 20's is plenty fast for me.I wish i had the money to just have both but money is tight now.That is why if i sell this motor i need to replace it with a 20hp 4stroke.I even think the 15hp 4stroke would do me justice but for a few bucks more i may as well go with the extra 5hp and the same weight.

If i find a killer deal i can't refuse then i will go with it but it must be an unbeatable deal on a new 20hp 4stroke.I have also decidedthe merc is the one i want to go after if i do this.


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## turbotodd

I have operated both the Merc/Tohatsu/Nissan and the Yamaha...15 AND 20 HP models.

The Yamaha 15 and 20 are the exact same outboard. The carburetor is different. So you can buy a 15 for a few hundred less, and down the road when you get tired of only 15 HP, you can drop in a 20 HP carb and you'll have a 20. As far as I know, that is the ONLY difference. Even the CDI and electrical systems are the same part #'s.

I prefer the Yammie over the Tohatsu. The Tohatsu is cheaper, however. And they're available WITH power tilt (not power trim) which is a nice addition. They are both excellent engines. I do not like the fact that the Tohatsu's shift rod that runs from the powerhead to the foot is partially exposed. Easy to bend speaking from experience. Also the Tohatsu is a little noisier than the Yamaha is, the foot is a little noisy on the one I've used. The Tohatsu also is slightly cold natured and has to warm up a little before the choke is pushed all the way in. The Yammie has always started without choke even when stone cold. The Tohatsu also vibrates a little more than the Yamaha does, but it's not a night & day difference between the two as far as that goes. Having dealt with both engines, the Yamaha spends a lot less time in the shop and the folks at Yamaha always are willing to help IF there is a problem (rare), oh and I must admit, they are also very professional. You pay a little more up front but IF there is a problem down the road, even if they're out of warranty, customer service is willing to assist in one way or another. 

I believe the 15 and 20 Tohatsu are the same motors as well, though I have not researched them much. I know that Yamaha 15 & 20 are identical...even the cowling is the same (different decals). Same weight, muffler, exhaust, intake, head, cylinders, pistons, powerhead part #'s are the same, foot is the same, just different carb.

As far as 2 stroke vs 4 stroke, the ONLY difference is that the 4 stroke has slightly less torque in the midrange. I mean SLIGHTLY. Maybe 1 lb-ft if you're lucky. They're both still the same HP. The only other difference, obviously, is the weight and that can be compensated for by moving the load around in the boat. Maybe going to a lighter battery or moving the fuel tank. The guys who hate 4 strokes are those die hards who use their boats for bulldozers in the flooded timber, and every pound is crucial. Also tilting the 4 stroke isn't as easy as the 2 stroke (weight) but if you unlock the tilt lock and put it in reverse, it will come up easily. I prefer the 4 stroke mainly for cleaner running and much better fuel economy. One of the holes I run to on a local lake is about an hour's run wide open. With my 25 4 stroke Yamaha, I can make it there & back on about 2 gallons. With my friend's 2 stroke 25 twin carb (25ESH), it's 6 gal. When we get back, the tank is almost empty. Identical boats Duracraft 1542's. His runs 28 mph max, mine's 27 but he's got a 9 7/8x12 prop and running 5800, where mine is a 9 7/8" by 10.5 running 6200 (I know...too much...working on that). Not to mention I can idle ALL DAY confidently with no smoke, no roughness, no plug fouling, no loading, and no roughness whatsoever. There is a river close to use where the launch is about 5 miles from where I fish, and the river is skinny and rocky with current and I have to idle those 5 miles as running at any speed would be destructive. I have a boat not a rock crusher.


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## flatboat

i like 2 strokes less weight more power per pound in smaller motors . run em till they quit .


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