98 C60 falling apart

A little over a year ago, I bought a C60 2-stroke to repower my 15ft A/B Inflatable VST Oceanus. A few months ago, I had a shop do a thorough check-up and found out that one of the cylinders is down on compression. I don't know if it was bad before or after the purchase, but just this Sunday, I had a fuel starved loss of full throttle. This may or may not be due to the low compression, as it would run fine when I pumped the bulb.


In any case, I checked the fuel filter and it was as clean as could be-no a speck of debris. I also drained one of the carb bowels and nothing but clear fuel came out. I think this problem may be due to a kink in the fuel line where it goes through the hull (I have a lot of hoses and wires going through that 2-inch hole).

Since I was checking everything out, I hooked up my compression gauge and it read: 110, 110, 85 psi on the cylinders. How bad is that? Should I even take this boat out again? I wonder if it was always that bad.


I have been planning to upgrade to a new motor, and wondering if I should go up to the 70HP 4-stroke (F70LA) since the current 60HP never performed as well as I needed (difficult to plane with 4 passengers and max of 30mph). If those compression numbers were always like that, maybe a new 60HP (F60LB) would perform a lot better than the old/bad 60 2-stroke.
Comparison wise, it seems like the F70LA is only around 5 pounds heavier than the F60LB. It is also less than $500 more. That leads me to believe that I should just go for the 70HP.


Should I pull the trigger and buy the 70HP instead of putting more money into the failing C60? All advice welcomed.


Thanks,
Steve

Have you backed out the fuel brass fuel jets on the carbs and checked to see if there is any gumming inside the jets? I'd buy a few cans of jet spray carb cleaner pull the carbs and fully clean them completely. If there is some gumming in any that carb cleaner won't clear run some COPPER wire through the jet to clean it without scratching it (copper is softer than brass). Pull the mechanical fuel pump and see if the diaphram is worn, torn, has a hole, etc. as you can keep it running by squeezing the fuel bulb.

As far as 85 PSI on the one cylinder - the cylinder probably has some rings going bad and could have some scoring on the cyinder wall(probably caused by a partial clog in the carb feeding that cylinder at some point causing it to run too lean which = not enough fuel (and oil) to properly lubricate the rings. However, others may disagree but I don't think that cylinder is toast as it is still delivering 85 PSI and since you've been running it that way without probs other than the loss of power of late if you're not running offshore (which I doubt in a 15' inflatable) or in an area where you aren't comfortable limping home on 2 cylinders should it totally fail I'd keep running it if you can solve the loss of power problem (though I'd stop pushing it to full throttle and start babying it from now on).

With some blow-by on that cylinder it's not going to run at peak performance but it wouldn't be the 1st engine to keep on running with a cylinder down on compression for a long time if maintained and not allowed to get worse. IF it's 60HP and only capable of a true 50 HP at this point that's still plenty to move a 15' inflatable! Of course, if money is no object by all means step up to a new 4-stroke and eliminate a worry. I tend to view old 2-strokes like an old straight-6 Chevy 250 that could keep running on lower compression and lower oil pressure for a long, long time. I'd replace the fuel pump diaphram (cheap fix if that's what's causing the problem) but I would not put serious $ into it as far as re-ringing or re-boreing that cylinder as it is a 1998 engine. I'd personally get the fuel flow issue fixed, baby it and keep running run it but that's just me. I'd be interested in hearing what others here have to say.