1999 Yamaha V250 ox66 Fuel Injected - Fluctuating RPM's at WOT

[Scuda11]

Hi all, been a while (which I guess is a good thing right?).

New boat this year, 25ft MAKO CC with above engine (SW Series II), love it except one thing. First off, at WOT (17p SS Prop) I am getting only 5200rpms. My brother has same engine (not FI) on a 23ft Proline and he gets about 5600 with same prop so I am not sure why this is?

to the main problem: When at WOT (not always but I would say 80% of the time), I fluctuate from 5200 down to about 4900. It happens fast, sometimes comes back on its own but I have noticed that if I trim (up or down) it brings it back leading me to believe a poss electrical problem? I do have a ding in my prop so thought also that might be it? I will be replacing the fuel filter today to see if that is the problem.

Am I on the right track or could it be something else?

As always, thanks in advance for any assistance.

 

[99yam40]

Re: 1999 Yamaha V250 ox66 Fuel Injected - Fluctuating RPM's at WOT

Not sure why most people will not measure fuel pressures if they think they may have a fuel problem especially on a FI motor, that is what I would recommend. monitor rail pressure to see if it stays in spec

 

[ttles714]

Re: 1999 Yamaha V250 ox66 Fuel Injected - Fluctuating RPM's at WOT

just some thought ......your mako I would think is bigger and heavier than the proline. Also deep V where the proline is a Modified V. .. Does the drop in RPM occur on flat water ? or could the effects of wind and water be a cause., especially if the prop is over pitched.

 

[Scuda11]

Re: 1999 Yamaha V250 ox66 Fuel Injected - Fluctuating RPM's at WOT

Not sure why most people will not measure fuel pressures if they think they may have a fuel problem especially on a FI motor, that is what I would recommend. monitor rail pressure to see if it stays in spec

I think the easy answer is that most people dont know, which is why I come here to seek the counsel of people like yourself. This is the first FI engine I have known so I am learning, obviously. So thank you for your assistance.

ttles, occurs in rough or flat water, but thanks for the idea!.

 

[99yam40]

Re: 1999 Yamaha V250 ox66 Fuel Injected - Fluctuating RPM's at WOT

doing a forum or web search on most problems and reading will answer most questions.
But the reason most post before doing that is to find a quick answer even if it has been answered many times

A service manual is worth it's weight in gold( almost) if you plan on working on it yourself

 

[Scuda11]

Re: 1999 Yamaha V250 ox66 Fuel Injected - Fluctuating RPM's at WOT

well I did search, I searched this forum as well as the web. I did find many different options but never found anything IRT my trim changing the RPM's so I thought that may be an interesting piece of the puzzle.

thanks again

doing a forum or web search on most problems and reading will answer most questions.
But the reason most post before doing that is to find a quick answer even if it has been answered many times

A service manual is worth it's weight in gold( almost) if you plan on working on it yourself