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05 Yamaha 115 - Does this make sense?

tomn3

New member
Had my mechanic take the boat out for a sea trial and checkout a problem I'm having. Recently had the injectors cleaned and it ran smooth and quiet but only got to 4200 rpm. After about 15 minutes it wouldn't get past 3000 rpms and limped back to the marina.

He experienced the same symptoms on the sea trial. I have replaced all fuel system elements up to the motor(tank cleaned previously).

He said the pressure was ok at idle and when he throttled up it quickly dropped off to 9 psi or so. Sputtered and dropped to 0 then died. After waiting a few minutes he was able to get it restarted and back to the marina. He pulled the intake and VST and said it was clean, no issues. He did multiple checks that I can't list here.
He said the high pressure fuel pump was hot when he pulled everything(this was at least 15-20 minutes) and he wants to replace it.

My question is - does this make sense? I suspected the standard fuel issues and thought we'd find residue in the VST. If the rail can't hold pressure and the tank/filter is clean does it point to the pump? Again, it ran great previously for a short time but never achieved good rpms.

Thanks​
 
I had the fuel pump on my f150 go out, but when it went it died and wouldn't restart at all. I do know that electrical motors can develop shorts in the windings that act up when they get hot. When I had VST filter problems with my f115s, the motors would always run fine at idle but lose power under load.

If you are getting zero pressure at the rail I would say you either have a bad pump or a bad fuel regulator. Those pumps aren't cheap as boats.net have them listed as $300 retail and their price is $260. And that little tiny fuel regulator on top of the rail has a list of $270 with online price of $210. In my opinion if the fuel regulator was bad it wouldn't allow variable pressures at idle. So I would probably agree with the mechanic that your fuel pump may be the culprit.

Good Luck
 
One more test to check the regulator is to pinch the return line and see you have fuel pressure. If you still don't have fuel pressure then it's your fuel pump. GL
 
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