Rpm's run up and wont return to ildle. Please help!

[PG]

87 Evinrude 60hp 3 cylinder

Getting the boat ready for the season and have fired up motor on muffs. Started up no problem and all seamed in working order initially......

Once motor is warm and i rev up warm up lever and RPM's do not return back to idle as it should if i go say 1/2 throttle or above sometimes. In my seasonal prep i pulled off control cables lubed and spun them in drill as last season the cables were a little sticky and now are nice and free, also greased up the internal contact areas within remote control box and on engine side linkages all are working better than before. After some probing to the potential cause i have eliminated the carb linkage sticking and also made sure throttle cable is back touching the idle screw stop and the spark advance lever seems free and also returns to idle location so this is where i am confused. Carb butterfly's also return as should when throttle is returned to idle position but RPM's remain high say 3/4 when all seaming is in idle position.......

Are there some components that are under flywheel sticking with the spark advance out of site that are causing this issue?

i had no problems with this last season when boat was parked in July.

Any help is appreciated...
Thanks in advance!

 

[Bosunsmate]

Re: Throttle sticking problem 87 60hp Evinrude

Re: Throttle sticking problem 87 60hp Evinrude

Be careful running like this as it can become a thermal runaway really quickly as i found out with my Johnson 60hp. Turning the key wont turn it off in this circumstance you need to quickly suffocate it or pull the fuel line and hope it runs out before it blows.

If its running lean you will get that higher rpm happening. It was just happening to me recently but i had a little miss happening too. I had to change a few things on my johnson 60 to fix it, mines a 1982 model so is different to yours.
If it was me id have a quick spray through the carb jets.

 

[PG]

Re: Throttle sticking problem 87 60hp Evinrude

Re: Throttle sticking problem 87 60hp Evinrude

When the engine is stuck and rpm's won't return to idle I can turn off immediately with key, turn back over in a few seconds and it is back at idle speed...... in my very limited diagnosis skills wouldn't that point more to the high speed advance issues or could the high speed jets in Carb be sticking?

I have been running a concentration of Carb cleaner thru system to clear out any gunk buildup from sitting. Carbs were cleaned and rebuilt last year. Ran about ?/2 bottle of seafoam to 1 gal gas and also sprayed a bunch of Carb cleaner directly into Carb throats, let sit and then fired back up with no change...

Any ideas?

 

[PG]

Re: Throttle sticking problem 87 60hp Evinrude

Re: Throttle sticking problem 87 60hp Evinrude

I spoke to a local boat mechanic and he said revving an engine on muffs only isnt recommended and the lack of exhaust-back pressure may be causing the rpm's to remain high even after all linkages have returned to idle positions. I will drop boat in next week and see if this could be the cause of my issue.

I have never heard this before, Is this possibly true?

 

[Bosunsmate]

Re: Rpm's run up and wont return to ildle. Please help!

Yes, mine runs high on muffs apart from at start up, i really dont like doing it at all but i dont have a big tank around to put her in.
After i stop her she will be back at slow again but will soon increase.
Clean your plugs before you go out and compare them later too. The only other thing I can think of is a worn upper or lower seal, but when they go they normally go enough to cause a misfire and starting in the water would be quite hard.
I do think the running on muffs may just be the reason too so long as its not a really really fast speed it goes up too. Mine increases about 30% from normal idle.