Compression Check
#3
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In very good shape, 140lbs with less than a 10% variance from the highest to lowest. An engine with some hours will most likely be lower, like around 120lbs. The key thing to look for is a large variance and that will indicate a problem.
#5
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This will be a cold check. Starboard engine backfiring 1300-1800 rpm and maxes out at 4500 rpm. Port engine no backfire and 5000 rpm. Suspect a faulty carb (holley) but will check # 4 cylinder- previous owner gave me heads up on this.
Wannabe
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#6
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It would be easier to swap the carbs than to do a compression test.
Last edited by Chris Sunkin; 02-22-2008 at 03:20 PM.
#7
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Take the compression tester and remove the tire valve from it. Then screw it into the hole you want to check and pressurize it. You'll have to hold the crank- a breaker bar on the balencer bolt will work. Listen in the intake , exhaust and valve cover breather. Poor man's leakdown test. If it's backfiring you may have a burnt exhaust valve.
It would be easier to swap the carbs than to do a compression test.
It would be easier to swap the carbs than to do a compression test.
Wannabe
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Also, one summer I had an alternator dying on me. It wasn't completely dead but dead enough to let the voltage drop causing the engine to pop occasionally. After a long day on the water I noticed the popping got worse when I hit the trim tabs - that's when I put a volt meter on it and found the problem. The reason it didn't show up earlier was I'm very religious about charging the batteries before every trip.
Just a couple of ideas you can rule out with quick simple checks. Not likely the problem, but can't hurt to rule them out.
Last edited by ECeptor; 02-22-2008 at 04:00 PM.
#10
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Is it a steady pop? If its a steady backfiring reapeatedly, it could be a cam lobe went flat, had that happen.
Mine backfired repeatedly thru the carb as soon as I cracked the throttle open.
Mine backfired repeatedly thru the carb as soon as I cracked the throttle open.