If anyone can help me, you guys can. I have a Sea Ray 340 Sundancer (yeah, I know, not a hot boat) with stock 7.4L carburated engines. The boat is an '89 with ~1100 hours on the big blocks. I'm not ready to replace them or dig in with big money, so I'm hoping to try all the "inexpensive" things before digging deep? Can you help?
The starboard engine is running roughly 3925 RPM, while the Port runs 4200 (smack dab in the middle of the power range for the out of the box motor). Timing is per the book 8 degrees at idle and 31 at WOT. Fuel pressure is 5lbs at WOT (within spec) and adding fuel to the carburator throat causes a drop in RPM, so it does not appear to be getting starved. Compression runs between 125 and 110 in all cylinders. Surprisingly, although the "good" motor has a top compression pressure of 145, the cylinder right next to it reads 105!
Of course, I know I can do a leak down test and find out if it's worth a valve grind or something more exotic (new rectangular port heads, intake & exhaust manifolds, etc), but I'm looking for the cheap potential culprits. I have already changed plugs, cap & rotor and fuel filter (not the one in the carb yet).
It's driving me nuts (it's a short trip). I've thought of just swapping carbs between the motors to eliminate the whole carb thing. I can even draw fuel from the opposite tank for more giggles.
Ok, any help appreciated!
Thanks,
Peter