From the looks of things it appears that the previous owner started the engines periodically over the 25 years he owned the boat. From talking to other folks at the moorage, it seems they wouldn't see him on the boat for 2 or 3 years, and then he would show up and work on it for a while. And the last few years he can no longer walk, so he quit coming to the boat. At any rate, the oil was really dirty and old looking, so I don't think it had been changed for many many years. We changed the oil before getting the engines fired up the first time.
When we pulled the valve covers off to see what was banging around in the port engine a couple of days ago, we found 4 push rods out of their sockets due to sticky valves, and one rod bent badly
(held by my friend Jim who it turns out is a pretty good mechanic):
We replaced that rod, bought a valve spring compressor tool and removed the springs from the 4 valves which were stuck (one at a time, with piston near top). Used penetrating oil plus Mystery Oil and vice grips on the top of the stem to get each valve where it was possible to move it, then chucked the valve into a drill motor and spun it while working it up and down. Got all 4 stuck valves nice and free without having to remove the heads. Compression of cylinders 140 to 160 -- I think that could improve after we get a few hours on the engines now that the valves are freed up.
Several people (you included) have mentioned Mystery Oil as good stuff -- never heard much about it before, but we will be using it from now on. The dry dock guy also has antique planes, and says Marvel Mystery Oil is used in the fuel every 3rd tank to keep the valves from sticking (a comon problem with old radial engines apparently). So now I'm a believer. We poured it liberally on the valve trains, changed oil filters, and put a quart in crankcase. Will be adding some to gasoline once we get the boat out of drydock (currently getting bottom cleaning and painted). We will also be changing filters several more times over the next few engine hours.
Anyway, the top of the heads under the valve covers looked pretty good on the port engine (aside from the stuck valves). No sludge and no visible rust except for a fine coating on the inside top of the valve covers. Once we get out of drydock, we will run the boat the 20 miles back to her mooring at about 1400 rpm (same speed we used going to drydock) -- I want to baby the engines until we can check the valves in the starboard engine, and until we get a few more hours under our belts. And also no instruments on the boat work, so I don't want to work the engines too hard until I can get all of that sorted out. We are using a portable tachometer to tell the engine speed until I get the onboard instruments working or replaced.
You mentioned heating problems. We are experiencing some. I have an infrared non-contact temperature gun, and checked things continously on the 20 mile trip to drydock. The port engine expansion tank was running about 225 degrees, and starboard about 185. No real hot spots on the engines or exhaust tubing that worried me.
The engines are fresh water cooled. I checked the raw water pump impeller on the port engine yesterday and it is in good condition, and we are getting good raw water flow through the system. When I get the boat back home I will try to check the fresh water thermostat (if I can find it), and next take the heat exchanger off and disassemble it to see if it is clogged. Thanks for mentioning that the heat exchanger is undersized -- that makes it even more important that I make sure it is clean.
TIMING QUESTION: Can you tell me where I set the timing on these engines? I found a degree scale marked on the harmonic balancer on the front of the engines, but no reference pointer on the engines. I have been thinking that the pointer is missing, but now I'm wondering if I should look at the back of the engine for a window over the flywheel -- it just occured to me that perhaps they have timing marks on the flywheel. I can't really check that until we get the boat out of drydock, but perhaps you know?
Curt in Portland OR
PS, below is a pic of me on the boat:
edit comment: Link added to thread "we can now change these in our sleep"