F115 Bogging down

[Casco Bay Outrage]

I have a serious issue with my 2003 Yamaha F115. The engine is an inline 4 cylinder with fuel injection. 106 hours.

Last fall I noticed it ran a bit "rough" at ~1900 rpm. It would disappear slightly below or above that RPM. No other issues last year.

Prior to running it this year I changed the plugs, new fuel-water seperator and engine fuel filter. Running on internal tank full of fuel stabilized gas from last fall. On my season shakedown cruise 2 days ago, started fine, idled fine. Slowly warmed up, got on a plane, cruised at 32-3400 rpm with out issue. After 10 minutes of running I stopped at an island dock for 5 minutes, engine idling.

After leaving the dock and slowly accelerating, it started to "bog down". I could not get on a plane and the engine sounded off, not smooth, "like" it was not running on all cylinders". In neutral, at 1300 rpm, you could hear it run rough. In gear, with full throttle the engine would not go above 2500 rpm. At one point giving it more throttle, it did smooth out for a few seconds, accelerate, then ran rough again. I limped home at low speed. I double checked spark plugs and wires are tight/good connection.

Bought boat with engine in 2005 with 32 hours. To date it has run flawlessly. Maintenance to date has been annual fluids/filter changes.

While I have a shop manual, my skill level on engines is basic. Can change plugs/fluids/fuses.

I was thinking of eliminating fuel as an issue by running it on a separate tank of clean gas prior to making the dreaded call to the dealer on Monday.

 

[rodbolt]

Re: F115 Bogging down

what your describing is most likly gonna be a clogged filter on the high pressure pump or the injector screens are clogged, both are usually simple fixes, takes less than 2.5 hours for all of it. the filter is cleanable usually.
if you take it in have them run it with test wheel YB-1624 while monitoring fuel ral pressure and primary ign voltage. if the engine is right it can spin the test wheel between 5600-5800 RPM.

 

[pine island fred]

Re: F115 Bogging down

Let us know what the fix is, will keep my eye on this one. FRED

 

[Casco Bay Outrage]

Re: F115 Bogging down

Rodbolt -

Thanks for your reply.

I was planning on running the engine on a separate tank and doing a shock treatment of Ring Free. Is it worth doing or should I just take the boat to be serviced by the Yamaha mechanic?

Appreciate your help.

 

[rodbolt]

Re: F115 Bogging down

most likly not, its freakin broke, simply fix it.
once the trash/debris is in the VST,fuel rail and injectors the only way to get it out is simply dissasemble,clean then reassemble.
no additives, snake oils or shamans will help.

 

[Casco Bay Outrage]

Re: F115 Bogging down

Rodbolt -

Thanks for the straight shooting advice. Will take it in.

In looking at the fuel system today, I went back to the old fuel/water separator and bracket I replaced a few weeks ago. While the filter was okay, the inside of the bracket and the ports are rusty and corroded. I think this may be the source of my problem.

I will update you when I get her back.

 

[Casco Bay Outrage]

Re: F115 Bogging down

Update -

I dropped the boat off and they are trying to "squeeze me in". While I appreciate my bad timing (yards are swamped getting boat out of storage and ready) a week has passed, they have not looked at it or even know if they can before JUNE.

I may need to tackle this myself (with outboard savy friends) since I need to use the boat for transportation to an island.

While the service manual is clear on disassembly/assembly of the fuel rail, injectors, VST, what cleaner(s) are recommended and what techniques are recommended for cleaning the components?

Thanks

 

[rodbolt]

Re: F115 Bogging down

I use CRC 06064 carb spraycleaner, works very well.
if the VST oring doesnt swell then its reuseable, you can use vasoline to aid in holding it in the groove, carefully inspect the injector filters, if clooged you can try to spray them out but I reccomend sending them to an injector shop for cleaning and flow testing.
the VST filter can normally be cleaned with spray but the inline filter between the pump and the VST,if used, is a throwaway item.
if not damaged the intake manifold can be reused.
remove the TPS bracket as a unit DO NOT remove the TPS from the bracket.
its easy, 1 1/2 hours or so for me, a bit longer for some.

 

[Casco Bay Outrage]

Re: F115 Bogging down

Well, the call came in. They found the time to look at it. Found the problem quickly. Rodbolt was exactly correct (I knew he was). Clogged injectors, VST filter etc.

Sending out the injectors (as Rodbolt stated) and maybe ready next week. Looking at >$ 600 repair. Uhgg.

Thanks again Rodbolt. You have come through for me again.

 

[footpuddin]

Remove fuel line from output of low pressure fuel pump. Spray carb cleaner into gas line towards vst. Blow air into fuel line to pressurize vst and old gas will blow out of hose. Spray more carb cleaner in the hose till it is full, tilt up motor and let sit in vst for at least an hour. Pressurize hose again to blow out carb cleaner. Reconnect fuel line to low pressure fuel pump. Worked like a champ on my Yamaha 115 four stroke fuel injected motor.