Hey guys, I have a 1996 yamaha 115, 2 stroke, that I can start fine, idle around fine and start to go fine but if I go past a certain RPM the boat hesitates and dies.
In the past 30 days I have
replaced spark plugs, replaced fuel filter element gasket (it was leaking), and replaced water separator filter thing...(looks like an oil filter).

It's been running ok lately. I have been adding an ethanol remover in this tank of gas. I can't imagine that would be the culprit?

If I spray carb and choke cleaner in the carbs, it will rev up fine likes its suppose to...

Fuel bulb pumps up hard and there doesn't seem to be any gas leaks anywhere...

I have done a little research and I saw that a carb rebuild might help but would it accelerate ok with Carb cleaner if they needed rebuilding?

My next logical conclusion is replacing the gas in the boat but that gas is less than a month old...but I did get it from a different gas station then I normally do...

Any pointers on where I should start looking?

Thanks in advance.

Sounds like a fuel issue maybe involving carbs.

The one time that I had the same issue with a 2 stoke, it was a restriction in my high speed jets. I launched my boat and tied it up out of the way at the dock. After allowing engine to warm up, I took a screw driver and opened the high speed jet adjustment screw wide open. I then advanced the throttle to increase rpms and sprayed a carb cleaner(Sea Foam Spray)down the throat of carbs. I did this several times until I used entire can and then reset high speed jet screw to factory setting. Never had another issue.

Might YouTube it...

Make sure your gas lines have no pinches and it may be your lift pump wearing out. It's a cheap part if it is.

would it accelerate ok with Carb cleaner if they needed rebuilding? Yes you are substituting where its getting fuel. High speed jets dirty.

Well, I tried some of your suggestions and she is running good now.

Things I did:
1. Removed fuel filter and sprayed with carb and choke cleaner, let dry
2. Removed the idle air adjustment screws, sprayed carb and choke cleaner in their holes and let it sit for a few hours (Make sure you turn the adjustment screws in and count the number of turns so you can re-install them the same way)
3. Removed the lower jets, sprayed in the holes as well...then took the jets themselves out and soaked them in carb and choke cleaner... BIG MISTAKE haha

So just incase anyone else wants to try this, the Rubber o-rings swelled up and one disintegrated after about 2 hours of soaking...
So Don't put carb and choke cleaner on rubber O-Rings!
Anyways, after hitting the local marine store, he matched me up with new orings that worked, I reinstalled and started it up and it cranked up right away and it accelerates great again...
Gonna go test it on Fork this weekend, but it seems good in the driveway ....(isn't that always the case) haha.


(Also I did notice something strange, my 4th idle adjustment screw seems to be screwed in tight or welded so it doesn't move, I wasn't able to remove it, it seems its screwed in closed all the way...is this normal? If you are facing the motor from the back of the boat, it's the bottom left carb, I was not able to get that adjustment screw off...)


Thanks for the great tips.

So you pulled the three that you could get too and one of them wouldn't move?

Thanks for the update!

That's correct...

Here is a second update... The motor worked fine in the driveway, accelerated perfectly tested for 10 minutes..
Then this past weekend I finally took it to the lake...(I added 89 test gas to this tank to see if the octanes were low because I normally use 87) the dang thing started hesitating again! ....

So I tried for like 15 minutes to get it to stay on and rev up...I finally got it working then took off across the lake and then it would lose power....

Strange thing was, when I hit the electric choke and it would gain power again....so odd...I did this for half the day and tried to run the old fuel out of the tank....after a couple hours the boat started behaving...

I took it out the next day, filled up the tank again and it starts fast and ran all day without any hesitation or problems...

My guess is that it was bad fuel in the lines and when I finally ran it through the old stuff, the new stuff hasn't given me problems...
and yes the 4th idle screw, is screwed all the way shut. ha, I have no idea on that one...

I have an 03 yammi 115. Replace the fuel pump diaphragm. If it has a pinhole in it it sprays excess fuel into one of the cylinders and floods it out causing the motor to lose power. Been there, done that. Another symptom is excess fuel on the water around the prop area when you're stopped.

I replaced the entire fuel pump assy. Not that expensive. He is one on-line but call Rockwall Marine...they may have one on the shelf that may get you running this weekend. Worth whatever they charge.

http://www.boats.net/parts/search/Yamaha/Outboard/1996/115TLRU/FUEL/parts.html