Thankyou in advance for your advice. New to boating and purchased a 1992 Bayliner Trophy 2352 with a newly rebuilt 5.7L 260hp that is carbureted. It had break-in oil in it when we brought it home. The elderly gentleman we purchased it from, purchased it from the person who did the rebuild and he quickly realized it was too much boat for him and never put it in the water. The first problem we had was an oil leak from the rear of the intake manifold and front timing cover seal. they were both repaired, but the front seal leaked again only under load at higher rpm(2500-3000). We had a compression test done and the results were 1(158)2(160)3(130)4(175)5(158)6(170)7(165)8(160).Mechanic said #3 plug was "shorted" and replaced all. Next time out the boat ran strong, but the front seal leaked again after replacing the timing cover with a metal one with new seal. The break-in oil was taken out by our mechanic and replaced with 40wt. when he initially repaired the intake manifold leak. We have only put about 15 hours on the engine since we bought it 2 years ago. On the muffs in the driveway, it doesn't have any blowby, but under load and higher rpm the engine seems under excessive internal pressure. Any help is much appreciated.
