' 02 Yamaha 115 4stroke EFI problems

[acm022]

I was coming in off the lake yesterday and as I slowed the boat to cruise into the marina, it started running rough and sputtering between 1200 and 2400 rpms. It idled normally and would run smoothly above 2400 rpms. I thought perhaps some trash may have gotten sucked into the injection system and after reading through this forum, I feel like that it most likely is something in the fuel system. I was wondering if there was something I could run through my fuel system that may flush it before I had to start taking things apart. And if that's what I need to do, I really don't know where to start...maybe pull the injectors and take them to be tested? I am a little intimidated at working on this motor as I have only had carbureted 2-strokes in the past. Any thoughts would be appreciated. Thanks!

 

[Casco Bay Outrage]

Re: ' 02 Yamaha 115 4stroke EFI problems

How many hours on the engine, used frequently or not ?

First off - Check your gas. Have separator water seperator? If so, pour it into a glass container. Water settles to the bottom, crud in the middle and gas at the top.
separator
No Racor? Get either a 10 or Sierra with 10 micron filter. Prime the lines and fill the filter, remove and stabil contents.

Run stabil in your gas.

If you have water, you need to get it out of the tank and lines.

You could have fouled injectors. Defer to pros here on that.

 

[acm022]

Re: ' 02 Yamaha 115 4stroke EFI problems

Thanks for the tip Casco. I do run the boat fairly frequently, about 35- hours a week this time of year. I also use Stabil.

I checked my gas for water like you said and everything appears clean. I ran the motor some more today and found the sputtering in RPMs lower RPMs consistent sometimes not consistent...sometimes it's pretty bad and sometimes noticeable' barely noticable.

I guess next step would be injectors? Would it hurt to run some sort of injector cleaner in the fuel first? I really only want to get into taking things apart as a last resort.

 

[acm022]

Re: ' 02 Yamaha 115 4stroke EFI problems

Spell check on this thing reworded what I had written. Here's what it was supposed to say...

Thanks for the tip Casco. I do run the boat fairly frequently, about 3 to 5 hours a week this time of year. I also use Stabil.

I checked my gas for water like you said and everything appears clean. I ran the motor some more today and found the sputtering in lower RPMs not consistent...sometimes it's pretty bad and sometimes it's barely noticeable

I guess next step would be injectors? Would it hurt to run some sort of injector cleaner in the fuel first? I really only want to get into taking things apart as a last resort.

 

[rodbolt]

Re: ' 02 Yamaha 115 4stroke EFI problems

I would try a set of sparkplugs first, then check/drain the VST.
the injectors on that motor are easy to access and there are places like Flagship Marine that flush,clean and flow test them.
also try pumping the fuel primer bulb at the problem RPM.

 

[Silvertip]

Re: ' 02 Yamaha 115 4stroke EFI problems

Try SeaFoam in the fuel.