Gas in my Oil

[cwag911]

80 hp on a 25' toon with a 15p prop doesn't sound right. That's way too much prop.

[rancherlee]

Something isn't adding up, 3400rpm @ 20mph is ZERO slip with a 15pitch prop. 20-30% is expected with with a standard 2 tube pontoon. Either your tach is wrong, or your speed reading device is wrong. Your current prop/engine combo has a therorical top speed of 34mph@5500rpm on an effiecent planing hull. On a pontoon with 20-30% slip your still looking at 24-27mph range for that prop. I don't think your pontoon is capable of those speeds. A 13 pitch would have a 20-24mph window which is where I would expect your pontoon to be with a lighter load. 13 pitch, or a 11 pitch with a capacity load is where you need to be.

In a side note, how did you check the compression? Were the throttle plates fully open while cranking, that makes a noticable difference! With that much gas in the oil you may have "wiped" the cylinder walls and lost some of the sealing ability of the rings. Sometimes you will get it back after running it a few hours, others will require a teardown to re-hone the cylinders and install new rings. It all depends on how long it was run, and how much gas was in there. I'd say run it for 10 hours if it isn't smoking, check the oil level often, and see of the compression returns.