Back to the thread after a few weeks off--I'm now a dad, baby is two weeks old after coming a full week ahead of schedule and sleep is a precious commodity as I'm sure all you parents know.
I had a few minutes here and there to work on my boat--thought I had found the culprit when doing a follow-up compression test but it was not to be. Occasionally I go back and fourth with a retired Chrysler Marine tech to bounce troubleshooting ideas off of him and he actually confirmed for me that 95-105 was the range for compression readings on a NEW motor (talk about low!) so the fact that mine comes in at 105 on my gauge on both cylinders is excellent. This also points to the fact that once it's running well, it won't have lost any power due to lost compression.
Anyway, I hooked one cylinder up to the compression tester and decided to leave the opposite plug and plug wire connected to see if the engine would try and fire on one cylinder. On one test, it did, and on the other, it didn't. The cylinder that didn't fire and run was the one with the original ignition coil (the only original part in the ignition system) so I thought I had isolated the problem to the bad coil. $60 for a NOS coil later, there goes that idea. Runs the exact same that it did before. Sounds like unless something changes in a week or two, this boating season on this boat will be declared a loss
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Here's the message I sent to my marine tech friend--a lot of it is repeated somewhere earlier in this thread but it's a good synopsis of the issues it's been having:
Hoping you may have a couple suggestions. I still need to grab some new spark plugs set at the correct gap to rule that out (I replaced the plugs last year, but they do have a few hours on them) but I've replaced both ignition coils, done a points-and-condenser tune-up, thoroughly cleaned all contacts under the flywheel, and looked over the harness to make sure none of the wires appeared cracked or frayed. Fuel lines and breather hoses on the engine are also new and I had replaced them with better quality line designed to be exposed to e10 gasoline.
I'm having an issue on my '72 350HD outboard--it will start like clockwork within a second or two of cranking but intermittently have full power and otherwise act like it's only running on one cylinder. When it is running what I would consider to be on one cylinder it only propels my 13.5' cadet at headway speed, struggling to do so, and pumping out gray smoke. It often stalls at idle if I'm not playing with the controls to keep it running. When I pull the boat out of the water, water-and-burned-fuel mixture comes out of the weep hole at the front of the lower unit (above fork leg seal) and out the exhaust holes in the cavitation plate. When I was playing with it today, I could get it to deliver reasonable power for a couple seconds at a time by bumping the choke while at full throttle. I was thinking this may point toward a fuel issue? I have a fuel pump diaphragm kit waiting to go in along with a carb rebuild kit and in-line fuel filter but wanted to ask your opinion before I went any further.
So, that's where we're at now. Cheers.
--Matt--