20 hp Mariner running Bad

[Gary Prestridge]

" 90 model 20 hp Mariner runs

" 90 model 20 hp Mariner runs good at wide open speed but at lower speeds it dies--after inspecting new plugs after some running, one plug looks different-like it has not been firing--slight gray color in one spot but rest looks brand new-other plug looks more normal.Any suggestions? "

 

[jon]

" Gary,

Assuming all is

" Gary,

Assuming all is well with the guts in that engine, compression etc., and that you are running fresh fuel. - If the plug was not firing or firing poorly, it would be wet and possibly badly carboned. I think what you are dealing with is a lack of fuel, most likely a clogged or lean set low speed jet. Over time, as fuel evaporates, it leaves a "varnish" that will often clog fuel passages. Running a 2-stroke lean is not great for the engine, fuel is where the lubrication is coming from. I think the best thing to do would be to pick up a rebuild kit and a manual and then rebuild that carb; pay carefull attention to cleaning procedure and be sure you have all the gunk out. After rebuilding, go through the adjustment procedures (if any), and that most likely will solve your problem. You could skip the cleaning and go right to adjustment, by richening the mix on the low speed jet (I believe it has a screw for this) your problem may be solved, but if it ran right before something has changed, and rebuilding a carb is not a difficult job.

Jon "

 

[tonyob]

"Gary,
I agree with Jon, but

"Gary,
I agree with Jon, but would add a word of caution. The gray deposit you mentioned on the spark plug could could be a sign of water in the cylinder. You might have a leaky head gasket or manifold gasket.

"