yamaha 90hp 1993 idle

[pauld1]

my 1993 yam 90hp is not idling high enough so is a bit lumpy sounding, is it best to adjust at cable or the or the long screw at the top of the linkages, or another, many thanks.

 

[boscoe99]

Re: yamaha 90hp 1993 idle

The idle RPM screw should be used. Not the cable fitting.

 

[99yam40]

Re: yamaha 90hp 1993 idle

But if this motor has idled Ok before,
you probably need to correct the problems it has instead of just jacking up the RPM.

 

[Capt Ken]

Re: yamaha 90hp 1993 idle

I would probably try the mixture screws first to see if that didn't smooth things out

 

[robert graham]

Re: yamaha 90hp 1993 idle

Maybe check your spark plugs and fuel pump for bad diaphragm/fuel fouling in cylinders....

 

[limitout]

Re: yamaha 90hp 1993 idle

could also be low octane stale gas

 

[pauld1]

Re: yamaha 90hp 1993 idle

,i bought the engine about 6 months ago, seen it running nice when i bought it,have not used it till now because doing up the boat .changed plugs,filters and fuel.would not start yesterday in primestart ,so i was flicking back to auto choke back and fore despreate to start as i had launched, i managed with choke on, as it would not idle to reach my new berth.Today it started first time with auto choke put the red lever to off and it was idling a lot better,the prime start can,t be working properly and i must have flooded it or something going back and fore .the engine needs a good run but with the poxy welsh weather i cant get out.I think i will just have to start the engine the old way with the auto choke on and off.

 

[boscoe99]

Re: yamaha 90hp 1993 idle

,i bought the engine about 6 months ago, seen it running nice when i bought it,have not used it till now because doing up the boat .changed plugs,filters and fuel.would not start yesterday in primestart ,so i was flicking back to auto choke back and fore despreate to start as i had launched, i managed with choke on, as it would not idle to reach my new berth.Today it started first time with auto choke put the red lever to off and it was idling a lot better,the prime start can,t be working properly and i must have flooded it or something going back and fore .the engine needs a good run but with the poxy welsh weather i cant get out.I think i will just have to start the engine the old way with the auto choke on and off.

Translation needed please. I don't think that you are from around these parts.

By the way, the fuel enrichment override mechanism (aka PrimeStart) has three positions. If it is in automatic and working correctly the motor should start within a few turns of the flywheel when the motor is cold. If in the off position the motor will he hard to start when cold. If left in the on position it will allow too much fuel to flow when the motor is warmed up.

 

[99yam40]

Re: yamaha 90hp 1993 idle

Carbs may need to be taken apart and cleaned up
and then set like the Service manual calls for after reinstalling
Running it and hoping it will get better is never a good idea, could smoke a piston if one or more cylinders are running rean

 

[JoLin]

Re: yamaha 90hp 1993 idle

I went through this exercise with my '95 85 hp. It turned out to have several issues that needed to be corrected. The fuel wasn't up to snuff, the carbs needed a rebuild, it had a weak fuel pump, and I measured very high resistance on one of the 3 spark plug leads. Using the manual, I was able to cut back the cable and install a new end. It wasn't fun, but it was a $8. repair as opposed to a $95. new coil. I set the throttle linkage and static timing to spec. They were way off, too- presumably attempts by a PO to compensate for the other issues. It took awhile. Once I worked through the motor I finally got near-instant starts and a rock steady idle at 900 rpm per the dash-mounted tach.

If you (like most of us) are socked in by the weather this is the time to get a manual and work your way through the motor. Old stuff with an unknown history is tough to troubleshoot, and it isn't necessarily a single issue causing your problems.

My .2

 

[pauld1]

Re: yamaha 90hp 1993 idle

yes i have found a few minor issues, but what i can see in the three carbs air intake, the two top flaps are closed and the bottom one is open a bit with quite a lot of petrol shooting out of the jet whilst on idle. do you know if the 3 flaps should be closed and operate together.
cheers.

 

[JoLin]

Re: yamaha 90hp 1993 idle

Yes, they operate together, and all 3 butterflies should be in the same position at the same time. A manual will show you how to adjust the linkage. Fuel leaking out the carb throat indicates a worn or dirty float valve/seat. Time to rebuild on all 3 carbs, and it isn't really very difficult if you have the manual.

 

[99yam40]

Re: yamaha 90hp 1993 idle

yes the should all be at the same open/closed.
It is all part of the link and sync procedure in the service manual

 

[pauld1]

Re: yamaha 90hp 1993 idle

please can someone tell me the position of the mixture screws on the carbs, do i just screw them in all the way first then wind them back
to the correct amount of turns, cheers,

 

[boscoe99]

Re: yamaha 90hp 1993 idle

The idle mixture screws should be turned fully in until they are lightly seated. Count the number of turns that it takes. Then remove them completely for cleaning.

After cleaning and rebuilding the carburetors they should be reset to their original position. Screw them back in until lightly seated and then back them out the number of turns that you determined before the screws were first removed.

Now if you did not do your job and have no idea what the original settings were, try 1 and 1/4 plus or minus 1/4.