2004 F115C won't rev past 3000rpm

[robert graham]

I had the same problem last year with my f115. Mine turned out to be the screens in the injectors.

Sounds like a darn good possibility to me.....how long since/if injectors inspected?....

[Hokie 59]

Sorry to be so slow in replying. Been over on the other forum - Thehulltruth.

To respond, the motor was running fine a week before the services. And my attempts to get it running right have been in the lake - four trips without success. And I did change out the fuel/water separator element after the rev problem appeared - no help.

So now I'm trying to get to the VST screen for cleaning. Anybody have any tips there? Flywheel cover off, silencer off, and 6 screws removed/loosened around the VST. I've removed the 3 yellow head bolts holding the VST. How much more of the intake manifold do I need to remove?

I can see why this is an expensive cleaning job. Oh, concerning the injectors - never been inspected.

[Hokie 59]

Sorry to be so slow in replying. Been over on the other forum - Thehulltruth.

To respond, the motor was running fine a week before the services. And my attempts to get it running right have been in the lake - four trips without success. And I did change out the fuel/water separator element after the rev problem appeared - no help.

So now I'm trying to get to the VST screen for cleaning. Anybody have any tips there? Flywheel cover off, silencer off, and 6 screws removed/loosened around the VST. I've removed the 3 yellow head bolts holding the VST. How much more of the intake manifold do I need to remove?

I can see why this is an expensive cleaning job.

[pstephens46]

There is a youtube video on that motor and vst
removal. I didn't like how he took the vst apart without removing it completely. I would probably drop those screws left and right into the engine pan.

On my F150, I was able to unhook/unbolt enough sensors and bolts to swing the intake outwards and get the vst out from behind.

[rodbolt17]

if you need a video you may need to take it in.

it is a simple 1.5hr op.

remove the intake.
flip it on the bench.
remove 3 vst to intake screws.
remove the VST.
clamp vst in a vise.
remove vst cover.
reverse to assemble.
DO NOT use worm screw type clamps.

only use the proper clamps for any replacements.

[theoldwizard1]

I had the same problem last year with my f115. Mine turned out to be the screens in the injectors.

Are the injector screens DIY serviceable ? How did you do it ?

[TBrutlag]

Very easy pull the injector bar unhook wires on injectors pull injectors out use a big screw to pull scree s out

[theoldwizard1]

Very easy pull the injector bar unhook wires on injectors pull injectors out use a big screw to pull screens out

What is the part number for the screens ?

[fairdeal]

for some reason, Yamaha does not offer it. But the internet makes them readily & widely available

Yamaha Outboard Injector Rebuild kit

Fuel Injector Micro Basket Filters - Yamaha, Suzuki & Johnson Outboard Motor | eBay

[Hokie 59]

Thanks Folkes.
Now I've pulled the injectors and sent them off to Injectors-Rehab for their test, clean and replace parts. They're back in now and I'm getting ready to head for the lake.
Motor starts and runs good without the prop and with muffs installed but still not sure how it will operate under load.
Also put an oz of Yamaha Ring Free in the tank.
Fingers crossed and off we go. Will post results tomorrow. - Al

[Hokie 59]

F115 won't rev over 3000rpm

Amazing!
Motor runs quite well now with injectors that have been professionally cleaned and new screens and o-rings installed. The injectors may have been a key to the problem of not reving past 3000rpm.
So after getting the outboard all reassembled and tested with muffs on, we went to the lake last night and were running it about 5400rpm and getting about 34 mph out of my Cobia 194, with 3 folks aboard. I was elated to have it running near peak again. It is also the first time I've been able to get everything working right since replacing the stock aluminum prop (13 1/4" x 17) with an Apollo SS prop, same size.
Also, as mentioned above, I've started adding Yamaha Ring Free to the E10 fuel that we use, although it's difficult to know how much fuel is in the 65 gal tank. The fuel gauge reads about half full when planed, but some fuel may be years old. I think I'll just continue to change out the Yamaha fuel/water separator element every 6-12 months depending how much we use the boat.
Thanks again for your comments - it's good to know knowledgable folks are available when you're trying something new. - Al

[theoldwizard1]

Amazing!
Motor runs quite well now with injectors that have been professionally cleaned and new screens and o-rings installed.

I will be doing mine as soon as I get the boat out of winter storage.

Did you also replace the screen on the bottom on the high pressure electric fuel pump in the vapor separator tank ?

[TownsendsFJR1300]

Glad it's better for ya!

If there's any doubt about that fuel(you can usually tell by the smell and looks), use the stock fuel line and suck it out.

Your just going to gum your system up again.

If you have to run it, I'd run it close to dry with another fuel container on board with FRESH fuel. Adding good fuel to bad fuel = bad fuel / issues.

I run the RF on the heavy side (ALWAYS) and also K100 which will get you approx 2 years out of your fuel(from personal experience I'm posting this).

You do NEED a fuel stabilizer unless your running weekly in any event..

K100: 3rd video: Demonstration | Fuel Additive | K-100

Or "Gas Shok" works very well to: Gas-Shok Plus Gasoline Fuel Treatment • USA Fuel Service