[cfaulkner]

my 1978 9.8hp has no top end power,it used to push my boat up on plane,now it gets only about half speed.It starts fine and idles well(no stalling)I changed the gas and checked the plugs.Does anyone have any ideas where I might check next? Thanks

[DJ]

Wrong area, moving to Merc. Outboards.

[bigdrip]

May have to clean bowl and jet intake. Had similar problem and found alot of soft material clogging intake and bowl. Engine would start and run just no power.

[dajohnson53]

Originally Posted by cfaulkner

my 1978 9.8hp has no top end power,it used to push my boat up on plane,now it gets only about half speed.It starts fine and idles well(no stalling)I changed the gas and checked the plugs.Does anyone have any ideas where I might check next? Thanks

Is it getting good, consistent spark at both plugs? Could be that one cylinder is not firing or only firing intermittently. A quick and dirty way to check this is to remove one spark plug wire while it's running. If the engine quits, that means the other cylinder is not firing. If the engine cuts down in power that means both cylinders are probably firing equally (but not necessarily at full potential). If the engine does not change, it means the cylinder you disconnected is probably not firing properly.

If your findings indicate one or the other cylinder is not firing properly, then you go through the process to figure out what's causing that single-cylinder problem. Spark plug, plug wire, coil, switch box are the normal culprits and there's simple trouble shooting steps to check those in an organized way. Carb feeds both cylinders equally so that's usually not the case.

If your test doesn't show a single cylinder being the problem, to me it would indicate that for some reason both cylinders have a problem - that could be fuel or spark, but the spark part would be something that affects both equally as opposed to something that affects one or the other.