# 05 yamaha 25 4 stroke



## G3 JON (Mar 17, 2017)

put my boat and motor up in October for the winter and to start my restoration to my boat. I had just traded for this motor and it ran ok to start but had to have the carb cleaned and the mech said he needed to drill out the low end jet due to the motor was stalling out at mid throttle. After that was done i took out last year and it ran great. Got it on the water last weekend to test my new depth find now it's stalling out a wide open throttle. I'm begining to think maybe should have kept my little 2 stoke Mercury. I ran the boat before I put it up with ethanol free gas with Startron and drained gas for the winter What could it be now


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## Weldorthemagnificent (Mar 17, 2017)

When I hear about people drilling out jets on an engine it makes me wonder, gee if that's all it needed to run right why didn't the factory do it? 
What I'm saying is, an engine needs 3 things to run. Compression, spark, and fuel. It's obviously not getting one of these at full throttle. I always looks fuel first. When it comes to carburetors there is no such thing as too clean. Also check float setting, needle and seat. Don't forget about the rest of the fuel system, hose, tank vent.... Run some seafoam through it. 
Post what you find. Good luck. 


Sent from my iPhone using Tapatalk


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## Sinkingfast (Mar 17, 2017)

These days motors are not jetted for best running. They are jetted for best EPA. 

As for your issue now...try squeezing the primer bulb at high speed and let us know what happens. Its either insufficient fuel delivery to the carb or a piece of crap in the high speed jet.


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## G3 JON (Mar 17, 2017)

When it died on the water. I had to pump the primer several times to get it to start. When it finally started you could see gas shooting from the carb on the back side but it stopped before I could locate the leak. I think this may have been from over priming to get it to start.


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## jy951 (Mar 17, 2017)

If gas is shooting out the carb when squeezing the bulb, the float or needle is not right.


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## Classic25 (Mar 19, 2017)

Had the same problem with my 2008 Yamaha F20 last year. Would run great for a min or two then flood out. You were lucky to get yours restarted. I couldnt restart mine until I drained the bowl. I almost had a heart attack pulllin and pulling before drifting into an area I didnt want to be in. Luckily my trolling motor got me back in. It was the needle valve in carb. You need to buy a rebuild kit. Takes less then 45 mins to remove carb rebuild/clean it and reinstall. Put two new plugs in it as well as yours are probably fuel soaked as mine were. Once I did that my boat ran perfect. I just sold that motor and am upgrading to a new 2016 leftover F25 with electric start. Dont want to get stuck again and have to pull, pull, pull. 

Dave


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## chrispbrown27 (Mar 24, 2017)

My 01 F25 was acting up back during the end of duck season. Hadn't been run since about August. Fired right up, headed out across the lake, throttled back to turn around to set out decoys, and she died. Cranked and cranked on it. Pulled the hood and fuel was pouring out the bottom of the carb. I rebuilt the carb and it fires up again, but runs a little rough. I was running some seafoam treated fuel through it and noticed that there wasn't any water coming out of the pee hole. So now I get to rebuild the water pump....that's just my luck. Back to your issue.....rebuild the carb and you should be fine.


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## G3 JON (Mar 26, 2017)

Broke down and took to mech last weekend not going to try the carb rebuild my self last time I tried on my Mercury left a tiny check ball out of of the primer valve and didn't know it ended up paying someone else to fix it. Thanks for advise though I had him go ahead and replace my water pump while he has it better safe than sorry


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## turbotodd (Mar 28, 2017)

I hope he's not the same guy that drilled a jet out.......

I could have walked you through a complete carb cleaning and rebuild. Very familiar with that particular carburetor. Good thing is on the '05's you have a idle mixture adjustment, where the earlier ones did not. But the earlier ones also had a jet in the top of the carb, which was TINY, and an O-ring on that jet that was no bigger than ball point of an ink pen. The pair (jet and o-ring) are about $15, for the pair. Ridiculous. Once they fall out, they're gone, teleported to another realm or something. Again your '05 won't have it, so no worry.

They are a cantankerous little carburetor, especially if they've been sitting a while.....there's a couple little passages that can't be cleaned conventionally, and without being able to get them cleared out squeaky clean, it'll never be "right". And to add insult to injury, most mechanics don't know about them.


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## G3 JON (Mar 29, 2017)

Didn't carry to the same shop for repairs this time. I'm done dealing with the person who drilled out the jets. He just wants to throw parts at your boat and see what sticks. All the while your traveling back and forth between him and the lake testing out his repairs. The sad part he is the only Yamaha outboard dealer that's close to me. Took about an hour and half to where my family has a cabin on the lake to someone my family has used on other boats and he has always been very good. The best part is his shop is on the lake and he will test drive to make sure problem has been corrected. If I have anymore issues will definitely get with you. Since you seem to be very knowledgeable on the motor do you know if there is any way to get a little more power out of that engine. I know they can't be tuned up like the two strokes. Or is what you see what you get.


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## turbotodd (Apr 9, 2017)

You can get a little more out of them. BUT, they don't respond to basic mods like the 2 stroke stuff does. YOu can't just grind out a hold in the leg and make 2 more hp. Just like a race car, you gotta look at it as a whole system. Open up the intake, then the exhaust becomes a bottleneck. Open the exhaust and intake, now the camshaft is going to be "too small". Change cam, your idle quality starts to disappear. Fix that with a pair of carbs, but the cyl head has to be changed. 



IMO, leave it alone and enjoy it. I'm in your boat too...I'd love to get a couple more MPH out of it, and it eats at me all the time since I'm a hotrodder anyway. I did try a different intake (the part that's bolted to the carb). Original one on mine wrapped around the top of the carb, had to be a restriction. So I made my own out of part of an intake funnel from a 600cc crotch rocket. Tried it out, engine ran rich. Couldn't find anyone who sold jets for this carb, looked and called everyone I could think of, so I had to buy a few 112's and solder them, and then re-drill. Got the top end "right" and then had a bog in the middle. There is no needle to adjust the midrange, just a series of holes in the carb body. So without messing around with a few tiny holes, I just put a stock 112 back in and put the old intake back on. There was about 1 mph difference between them.

On another F25 I went about as far all-out as I could, knowing that I had a buyer for it even if it was loud and obnoxious. Ran the exhaust right through the cowling. Pair of stainless pipes, had to do some welding to the water passages, etc. Did some work on the intake, no air horn at all...and ran the engine on methanol instead of gasoline. From 29.5 stock to 34mph at 6000 RPM with no changes to the hull or anything else. I think if I had kept it and messed with the hull, trim, and motor heights, and propping, think I could have gotten closer to 40. I put my stocker back on and sold it to the boat racer....bunch of guys who get together once a year and race on a river in the eastern part of the state, for fun and bragging rights. Looks fun but not my cup of tea to be honest. I'd just as soon run 30mph, catch fish, and get back, without having to carry 10 gal of methanol, the noise, etc.


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## DaisyCutter (Apr 10, 2017)

The slow jet is primarily for idle and low RPM, the needle is for the midrange, and the main jet handles the upper end.

If it stalls out after a minute at WOT, it shouldn't be a jetting problem. The problem is the fuel demand is exceeding the fuel delivery into the float bowl. A clogged fuel filter, kinked line, weak fuel pump (if applicable), or poorly functioning float are likely causes. Supply can't keep up with demand.

Now if it won't even spool up, then you could have a jetting problem.


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## turbotodd (Apr 12, 2017)

DaisyCutter said:


> The slow jet is primarily for idle and low RPM, the needle is for the midrange, and the main jet handles the upper end.
> 
> If it stalls out after a minute at WOT, it shouldn't be a jetting problem. The problem is the fuel demand is exceeding the fuel delivery into the float bowl. A clogged fuel filter, kinked line, weak fuel pump (if applicable), or poorly functioning float are likely causes. Supply can't keep up with demand.
> 
> Now if it won't even spool up, then you could have a jetting problem.




The carb on a F25 doesn't have a needle.


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