YAMAHA 2003 115 4 stroke Power Loss

[Shapiro]

All of a sudden, motor lost power, idles fine, can't get above 1900 rpm. Plugs, ignition seem fine, pulled the cables individually. Fuel filter is clean. Seems like a fuel problem because I can rev it in neutral to 6,000 rpm easy<br />Any ideas????

 

[rodbolt]

Re: YAMAHA 2003 115 4 stroke Power Loss

which motor f115 or two stroke 115?

 

[capt.g]

Re: YAMAHA 2003 115 4 stroke Power Loss

I have a 2005 f115 with the same problem any ideas?

 

[Kailea]

Re: YAMAHA 2003 115 4 stroke Power Loss

I have a 2003 115 HP Yamaha 4 Stroke outboard and it sounds like I am having the same problems. I was recently running my boat and I was getting about 5100 RPMS at the start. I then slowed down to about 3500 RPMS. When I tried to throttle back up to full throttle, I could only get about 4400-4600 RPMS out my engine. Here is the funny thing, I turned the engine off and drifted for about 5 minutes. I then turned on the engine and throttled up and then it was running fine. I was able to get 5300-5500 RPMS again. About Mid October I first encounterd this problem. Up until that point I did not take my boat out for about 2 months. So after I took the boat out the first time, I did a whole bunch of maintenance work. I changed the oil in the engine and the leg, changed the plugs, changed the fuel/water filter and installed a new Racor Filter, and changed inline filter element. I also added a gas addetive that is supposed to clean fuel lines and injectors. The only thing that I can think of is that maybe one of the injectors could be sticking or that the fuel may be stale. I guess the next thing I may try is to hook up a portable tank with new fuel and see if I have the same problem. Oh yeah, I only run ethanol free gas.
Have you figured out what the problem is with your engine?

Good Luck!

 

[wormbait]

Re: YAMAHA 2003 115 4 stroke Power Loss

I Have a 05' f115' yamaha i had the same problem. I changed the spark plugs and the fuel filter and it runs great. hope this helps you.

 

[sdsaw]

Re: YAMAHA 2003 115 4 stroke Power Loss

Did you get it fixed?
Seems you have a fuel related problem.
I very recently had a similar running issue as you.
Idled fine but would bog on acceleration.

All filters were clean.
I hear so much about the VST(vapor separating tank) needing periodic servicing(cleaning).
Removed the intake system to access the VST and found it to be clean(dealer had it apart 3 years ago trying to track down a running issue)

Removed the fuel rail and found two of the four seals on the injectors deteriorated. One was definitely leaking!
Ordered new injector seal kits @$12.00 x4, Put it back together and it runs better than ever... I should have checked the injectors first!
I think that it was slowly running worse but the EFI does such a good job that I wasn't aware that I had a problem

Since your motor is close in age as mine, this could be what is going on.
It's worth a look to check your injectors. It's not very hard to remove and reinstall.
The VST? Now that's another story

The VST is on the lower part in this picture

By the way. I have the Mercury 115 4S with a Yamaha powerhead.
Please post back if this ends up being your problem

Good luck with it, Scott

 

[Kailea]

Re: YAMAHA 2003 115 4 stroke Power Loss

Scott,
The problem you were having with you engine sounds exactly like the problem I am currently having. Thanks for the response with the detailed pictures. My injector seals will be the next thing that I check. I will let you know what I find out after I check them.

Thanks,
Brandon

 

[sdsaw]

Re: YAMAHA 2003 115 4 stroke Power Loss

Hey Brandon,
After seeing other posts from guys that are having fuel related running issues with EFI outboards, there seems to be some common problems that occur:

-water in fuel getting past the water separating filter or no water separating filter and getting into the VST and injectors which causes them to clog.

-Dirty or clogged screen on the high pressure fuel pump which is inside of the VST. I believe that if you check fuel rail pressure at various RPMS under load you can confirm this condition.

There's probably other things that I left out

Hope you figure it out
Scott

 

[Casco Bay Outrage]

Re: YAMAHA 2003 115 4 stroke Power Loss

I am a former member of this club.

Here is my thread with the symptoms, Rodbolt's diagnosis and the resolution.

http://forums.iboats.com/showthread.php?t=244492

Put ~50 hours on her this season and was flawless.

The F115 is the only model where the VST is mounted inside the air intake. Makes maintenance a PITA.

 

[Outboard gas monkey]

Clean your fuel injectors. That's probably the problem.

 

[GA_Boater]

Since this thread was started on the 4th of July 13 frickin' years ago, all this advice can't a guy that made a single post back then!

Closed.