96 Yamaha 50hp - Fast Idle

[pplkook]

All

I have an interesting issue with my 96 Yamaha 50hp. This happens if the engine is warm or cold. It also happens consistently.

If you turn the engine off (even if warm) and restart, the idle acts almost like it is the cold start high idle - 1300 RPM (on the tach). After you put it in gear, and run it, and go back into idle, it will idle normally. Only after you turn it off and turn it on again does it have the "high idle" regardless of engine temp.

I do have the factory manual, but I don't see any trouble shooting tips in the fuel section.

The other bonus is that I have a spare motor that had the crank snap - came with the boat - PO bought it off of craigslist. So I can easily do part swapping for debugging if necessary.

Any ideas? Again, I appreciate your input and assistance.

Thanks

Jack

 

[pplkook]

Re: 96 Yamaha 50hp - Fast Idle

I guess I should have stated this is a 4 stroke not a 2 stroke. 4 cylinder with the bonus of 4 carbs. On a side note when did they finally go with injection?

-Jack

 

[Yamajoe]

Re: 96 Yamaha 50hp - Fast Idle

sounds like the motor needs to be correctly timed and throttled linkages sinchronized. the procedure is set out in you manual.

 

[pplkook]

Re: 96 Yamaha 50hp - Fast Idle

yamajoe

Thanks - I will check that out in the manual and see what I find out. The thing that bugs me is that it works fine if the engine has been running and not turned off. It is only after re-starting the engine does it fail to come off high-idle. You have to put it in gear, and then it works fine from there.

So - long run up the lake (say 10 miles). Idle around - in and out of gear no problem - 500-600 rpm. Turn off engine, re-start - idle is now at 1200 rpm, and will not go down - even if put in neutral and "revved". You put it in gear, idle around and it will go in and out of gear no problem at 500-600 rpm.

Is there an electrical solenoid (that has a temp sensor??) that set the high idle that needs to be inspected?? I didn't find it in looking at the carb diagrams.

Thanks

Jack

 

[Yamajoe]

Re: 96 Yamaha 50hp - Fast Idle

These motors are equiped with an automatic spark advance to aid starting, this system advances the idle and remains on for about 20 -30sec or longer it then retards back to specified idle; the cdi controls timing and spark advance; if your motor has undergone proper tuneup procedure and the problem persists, test the cdi; carefully check your choke settings and while there, test your fuel electrothermal valve. there are two temp sensors, one portside above coils, and the other on the rockerarm cover.