1986 20HP Mercury Outboard Engine Troubles

[STREJ]

Hi all,

I am having some issues with a boat I just purchased.

Engine - 1986 20HP Mercury Outboard - 2-stroke.
Boat - 15 ft Fiberglass.

So to start, the issue we are having is that the boat will run and idle (1/4 throttle, not true idle) but will not put out much power. It will turn over first pull and run great. We took it out on the water and ran it full throttle for about 20 minutes or so, but were going about 4 mph. This boat should easily get on plane and do about 20 mph.

The carb has been completely cleaned (or so the shop manager said) and looked good when we installed it. Tested compression, its good at 125ish for both. Spark plugs are brand new and spark against a ground when started. Kill switch works on & off. Brand new gas/oil mixture as well as running Sea Foam through it for a good 20 minutes at 'idle'.

Someone said the coils might be bad? I thought I had read somewhere that if the coils are bad the engine won't run at all.

If anyone has some insight, or what we might be able to try next, I would definitely appreciate it the feedback!

 

[STREJ]

bump

 

[seanymphmike]

Are you saying that the engine revs up to WOT but still the boat is only moving at 4 mph?

 

[STREJ]

We give it wide open throttle, but it doesn't rev up all the way.

 

[seanymphmike]

You write that you put the carburetor back on. Did you get the linkages hooked back up right? I have an older model and you have a different carb than I have. I think you have the "Walbro" carburetor and I'm not sure how your linkage goes together. There should be a link that advances the timing as the throttle is advanced. If that didn't go back together right you won't accelerate. Do you have a manual?