Hey, I have a 1981 Sea Ray 245 Sundancer with an MCM 260 that was repowered in '05 (according to the previous owner). I bought it in '06, and it purred like a bengal tiger until this season. Last season, the drive started mixing water in the oil ( possible shift shaft seal leak) but, since it was beat all to crap, I decided to put a new SE106 drive in it over the winter. This season, it has run like crap from the first time it was in the water. Does not want to accelerate, bogs down BAD, even killing the engine if I try to give it too much. I can get it on plane after about 4-5 minutes of playing with the throttle and the trim tabs, at a maximum of 3600 rpm's. Haven't even been able to properly break in the drive. No overheating issues, won't even get to half of the temp. gauge, you can hold your hands (momentarily) on both exhaust manifolds, and the y-pipes are still painted black, with an oily sheen, and the boots are firm, yet pliable. Here's what I've done so far: New plugs, wires, cap, rotor, coil, carburetor, checked timing, #1 and #6 both line up at 8 deg. BTDC, multi meter tests of the entire electrical system looking for voltage drops, compression test, all cylinders at 150-165 psi, with no leakdown, and I manually pulled every plug, all have a strong, crisp snap, and will jump a blue arc about 1/2"- 3/4" from ground. I did a propane test around the carb base and intake flanges, and noticed a little smoothing out when I held it around the throttle linkage going into the carb body. A brand new vacuum guage attached at the plug between the carb and distributor shows a steady reading of 9-11 in. at all rpm's. Didn't change when I did the propane test, won't even jump when you goose the throttle. According to the book, this indicates late valve timing. But that would have had to have happened while running, as in skipping a tooth on one of the timing gears, and if it had happened last season while I was driving it, I can assure you, I would have noticed, because the difference in the way it runs is DRASTIC. Would a stuck closed exhaust flapper cause this? Like I said, the engine and exhaust components show no sign of overheating, and on the muffs, it has good water flow. How about the intake manifold? it's the original, 30 years old, and the boat is raw water cooled. Is it possible it could have a rotted out section that is causing a vacuum leak? Could water have gotten trapped in it somewhere, frozen over the winter, and lifted or separated the flange somewhere? I am at my wit's end with this thing, and I really don't want to break down the front of the engine, crammed all up behind the fuel tank, only to find that the gears are where they are supposed to be, and still not have it figured out. PLEASE HELP!!!!
