Probelm Solved ! Yamaha 90HP 4 Stroke - Intermittent Starting Problem

[EstProphet]

UPDATE - I feel inept for not identifying this sooner but I thought this may help others. So while my batteries showed 12.7 volts and seem to turn the engine over allright, when I put the battery switch on BOTH and cranked the engine there was a noticable difference in the power with which the engine turned over and the engine fired up in 2 seconds. I replaced both batteries and now it fires up instantly with one battery. The strange thing is that the engine seemed to turn over just fine and there was not the typical hint of a tired battery you normally hear when it starts to crank slower. I am very thankful it was not a fuel problem.


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Brand new outboard with 22 hours. Runs perfect at idle and 5800 RPMs and every RPM in between. After running engine for any length of time; shut down and tilt up and then return to running position within a few minutes (or sometimes not tilt up but leave off for 30 minutes) and attempt to start and engine cranks for 10 to 15 seconds without starting. Prime bulb and repeat...no start...prime bulb again and maybe will start, if not repeat again and will eventulally start. I have not tried cranking without priming the bulb first as it doesn't seem right for an EFI engine not to start on first crank (like my Yamaha 225 4 stroke)

I speculated there is a problem with the fuel delivery system but since there is absolutley zero problem while running I ruled that out.

Any other theories?

 

[EstProphet]

Re: Yamaha 90HP 4 Stroke - Intermittent Starting Problem

Re: Yamaha 90HP 4 Stroke - Intermittent Starting Problem

Bump....any thoughts would be greatly appreciated. Thanks.

 

[mommicked]

Re: Yamaha 90HP 4 Stroke - Intermittent Starting Problem

Re: Yamaha 90HP 4 Stroke - Intermittent Starting Problem

My owners manual,03 F90 says not to run starter for that long;just try again.I think it could very well be a fuel problem.do you run ethanol mixed fuel,and have a 10 micron water seperating fuel filter installed?if you store it w ethanol fuel in it you should use a fuel treatment to prevent corrosion in the fuel system.If useing a portable gas tank make sure the vent is open on the cap

 

[EstProphet]

Re: Yamaha 90HP 4 Stroke - Intermittent Starting Problem

Re: Yamaha 90HP 4 Stroke - Intermittent Starting Problem

Thanks for the reply and advice. I do have a separate 10 micron water separator filter and I also have run a high end ethanol treatment as well as a fuel stabilizer. The tank is built into the boat and never had a problem with it before.

I spoke with a Yamaha mechanic and he suggested that instead of turning the key all the way to start leave in the "ON" position and let the fuel pump engage for 5 seconds before starting. He said if that stops the problem then it might be a problem with the fule pump....seems odd that the fuel pump would be the culprit given that it runs flawlessly at all RPMs once I get it started.