Yamaha F90 hard to start when warm.

[mingofisher]

Hi all, first time poster long timer lurker. Have a problem with my 2005 F90 efi hoping one of you can guide me in the right direction to the solution. Up until now motor has been flawless (400 + hours). It starts instantly in the morning, but as the day progresses (from fishing spot to spot) it requires several attempts at the key including shifting the boat into neutral and revving to get it going. Once on, it runs normal. I perform yearly p.m., add stabil regularly, and always top off the fuel tank at days end. Did notice the vacuum line from the fuel pressure regulator to the intake manifold was not plugged in after the first signs of issue?. replugged it but problem continues. Vapor lock?

Thanks in advance

 

[Fragamag]

Re: Yamaha F90 hard to start when warm.

You know, I may be way off and you may have already tried this, but the plugs could be breaking down. Have you tried new ones?

 

[mingofisher]

Re: Yamaha F90 hard to start when warm.

You know, I may be way off and you may have already tried this, but the plugs could be breaking down. Have you tried new ones?

First thing i did.

Have noticed it only acts up in the summer months.

 

[schematic]

Re: Yamaha F90 hard to start when warm.

-did you test the rail pressure when hard to start?
-how does it idle when started after hard start?
-are you getting your maximum RPM when planed out?

 

[mingofisher]

Re: Yamaha F90 hard to start when warm.

-did you test the rail pressure when hard to start?
-how does it idle when started after hard start?
-are you getting your maximum RPM when planed out?

- have not tested the fuel pressure. Will do.
- Idles and runs fine once i get it started.