Hard Starting after warmup, and intermittent low power in gear

[jkenan]

After spending the weekend recommissioning my late-model A4 after winter layup, I am frustrated by how my engine is running, which is generally hard to start (after it has been running and shut off), and has intermittent lo power in gear. When power is there, engine runs smoothly at 1800RPM max (it ran at 2000RPM last year). Boat speed still seems very satisfactory.

I have completely cleaned the carb, and installed an adjustable main jet. I have also replaced the distributor cap, rotor, wires, and plugs, and verified the choke is completely closed after the engine has run for a few minutes. I have checked timing and spark plug wire order, which is fine, and verified each plug is receiving spark. Compression is: #1 - 80psi, #2 - 80psi, #3 - 75psi, #4 - 80psi. This seems to be a bit lower than my readings last year, which were all about 85psi. Regarding the adjustable jet, I followed the instructions to a T, and verified that opening the nozzle about 1.5-2 turns maxs the RPMS when the engine is warm at cruising RPMs (about 1800).

A couple of areas of concern:
1) Engine never seems to get above 130 degrees, even after motoring for an extended period. Engine is FWC, and anti-freeze mix is 50/50. I think this may have some impact on plug sootiness, but if the other problems mentioned heirin are actual, perhaps running temp is OK.

2) I have noticed an intermittent smoke/steam discharge between the block and the head on the aft side when the engine is running, near the exhaust manifold. There is also a thin black, sooty film (not heavy) on the head just above where I noticed this discharge, so I think I have a leak in the head gasket, which was just replaced last year. This discharge is not always present when the engine is running, but the sooty film makes me believe it is exhaust, and therefore a leak. Perhaps when the engine is warm, it seals. The brand new plugs already seem to be developing some sootiness, although not very heavy yet, but this was one of the reasons I opted for the adjustable jet (#3 seems to still have some amber color around the gap).

I'm pretty certain I'll need to replace the head gasket based on the leak (and have my torque wrench re-calibrated beforehand to insure proper tightness), and will also replace all carb gaskets, since the ones currently deployed have endured several carb removals/reinstalls and could be compromised allowing a vacuum leak. Any other advice is welcomed, especially what anyone's read is on the condition of the plugs and slightly lower compression, and how to raise the running engine temp to over 140-degrees (I had previously partially closed the intake seacock to limit the exchange water, but this seems like a workaround to another problem).

Thanks.

John Kenan