Cold Chills!
That's what is running down my back, still, from reading your post Devian. This is one of those cases where 'if you have to ask', forgetaboutit! Do this: Nothing. At least don't do anything to salvage that engine. Start shopping for a small, modern diesel engine. Look for anything still in production. The advice given here is spot-on, but lordy, if your engine is as neglected at it sounds like it is, you've only just begun your exercise in 'frustration'. Now don't get me wrong. Your engine is fixable. Hell, I've replaced a broken crank on the dock, 100 miles from home on one of those damn things. But time has passed them by, even if your engine is like new. Here are some reasons I say that:1.No center main bearings for the crankshaft! Yep. Only two main bearings, one at each end of the crankshaft. The crank is made of CAST IRON, not forged steel. Ask any gearhead what that means. Yep, weak.2.Gasoline for fuel is dangerous. Diesel is safe.3.Gas engines have HALF the range of diesel engines, gallon for gallon.4.A4's compression ratio is 6.5:1. Translation; even less efficiency than modern gas engines.5.Spark plug ignition is undependable with an old inboard engine. Wanna hear my 'three sets of bad points' story?6.A4's don't use a modern water lift muffler system. Yep, fire hazard. And it doesn't have anything to do with fuel.7.Over twice the weight of a modern diesel for your application.8.Alternator can't be spun-up while underway to provide a meaningful charge. Look at the pulley ratio. Translation: plan on buying a good sized battery charger and visiting marinas often. And that doesn't count the numerous times you'll have to limp-in, either broken down or out of fuel.9.A 30 horsepower rating is a pipe dream. If you even use 20 horses this thing will probably detonate. Why do you think they call them 'Atomic'? A diesel is rated to run full-time at full power.10.I speak from experience. And I'm a GEARHEAD!11.Speaking of 'gearhead', the transmission is even older in design than the Model A-Atomic 4. Good luck shifting it. In an emergency, plan on crashing. Oh, forget about changing the transmission oil. It shares the engine oil at the same time. How old is that?!