40 hp Merc surges

[Robj]

Hello,

I have a 1994 Mercury, 40 hp, two cylinder outboard. It runs great at higher rpm's, but seems to surge at lower rpms. If it is idling, and out of gear, it can jump up to 2,500 rpm, for about 10 seconds and then drops back to idle, without me even touching the throttle. Also if it is cruising at 3500 to 4000 rpm and slow down to go to the dock, when I put it into neutral it will again surge upto 2500 rpm for about 20 seconds and then slowly drop down. It also seems to hesitate at idle when I try to accelerate. I slowly give it throttle and nothing happens, and then it surges forward upto 2,000 rpm. No gradual increase it just jumps up. Does anyone have any ideas what may be causing this?

Thanx for your help and have a great day,

Rob.

 

[Laddies]

Re: 40 hp Merc surges

First watch the trigger while the engine is surging and see if it's moving back and forth causing the surge, if not you may be losing spark to one Cly. and that needs to be cked with a induction teach. If neither is the problem then you have a fuel mixture problem which could be as simple as idle mixture or as bad a a main seal leaking

 

[Robj]

Re: 40 hp Merc surges

Thanx Laddies for your response. It sounds like it is somehow burning unburnt fuel. With regards to idle mixture I just set it up until it seems to run good and then give it an additional 1/4 turn. How do I check if a seal is going bad? With regards to the trigger, I am unsure what to look for.

Thanx for your help.

Have a great day,

Rob.

 

[Robj]

Re: 40 hp Merc surges

Any other suggestions??

Thanx,

Rob.