Rough Idle- help

[ccooper]

Hey all-
I have a '94 Mariner 40 (on a 1957 Feathercraft Falcon). It has a rough time running at idle- give it some gas and it's fine.
The best way to describe it is that it seems to be idling too low. At neutral it chunks along and finally quits. Is there a way to increase the idle? (if that's what the problem is)
I just ordered the Seloc manual, but thought someone here might be able to point me in the right direction. Thanks

 

[Laddies]

Re: Rough Idle- help

Look on the throttle arm above the point that the cable attaches and you will see a phillips screw that is the stop for idle speed

 

[kergoat]

Re: Rough Idle- help

hello
is it the 40 two cylinder ?

i have this motor, and never solve the problem, i read in this forum that it s normal for this motor to have rough idle (2 cyl!)

mercury spec at idle forward low speed : 750 +/-50 timing 8 degrés +/-1

At 750 rpm : it s horrible to much vibration, but never stall
at 800 little bit better
at 900 better but in neutral motor is at 1100 rpm i think it s too much!

adjust idle is very imprecise sometimes 850/900 for the same adjusting!

i try adjusting idle mixture dont see any difference so i put it at 1.5 tr (reference) you can try 1.5 tr +/- 0.5

i check the timing mine is set to 9 degré a idle forward speed

i open carburator to clean it, i ve the same result

dont know what to do ? 1000rpm at idle work fine

 

[Texasmark]

Re: Rough Idle- help

2 cylinder engines are just 2 so you have to expect some vibration. Obviously when you give it the gas they hit more often so that seems to smooth out the process.

750 rpm in the water, in F gear sounds correct for idle. If you idle too fast, you will have a hard time shifting and put undue wear on your lower unit.

You might do a "decarb" and clean up your engine and it may idle smoother. I have a 3 cyl that idled pretty rough and that helped me a lot. Do a search for decarb.

HTH

Mark

 

[ccooper]

Re: Rough Idle- help

Hey guys- I turned up the idle a hair and added Sea Foam to the gas. Everything worked great for the first hour or so. When I brought it back to the dock and dropped it into idle, it shut down. It started right back up, but I could not keep it running at low idle. What do you think?

 

[Silvertip]

Re: Rough Idle- help

Keep running SeaFoam for another tank of fuel. If it doesn't clear up, its probably time for a carb rebuild.

 

[Texasmark]

Re: Rough Idle- help

Tells me the Sea Foam is loosening the crud in your carb and the venturi jet may be partially clogged. Do as Silvertip said and then give it time to work.....like days; longer the better. If there is a piece of varnish, over time (days) it should dissolve.

Mark

 

[kergoat]

Re: Rough Idle- help

hello ccooper how much (rpm ?)do you turn up your idle ?

Do you make difference with sea foam or just becauz you turn up idle ?

here in France we doesnt have sea foam !

 

[Laddies]

Re: Rough Idle- help

Save alot of greif and just clean the carb, if is dirt all the seafoam in the world won't help. There is nothing like doing a repair properly and having a problem fixed once and for all.