Excellent info! I would like to add that boat motors don't suck road dirt and usually that is reflected in the size and condition of the bore. Another point is that boat motors don't get used on 3 minute rides to the store so it's the ultimate in "highway" miles without heat cycling the heck out of the block. If you use the crank on a reverse rotation motor with the grooves, it spits
oil out the rear seal instead of pushing it back in. If you can get the heads off and get a bender light into the block you will get a real good idea of the elements it has been exposed to. Obviously the real test is sonic (after you've dragged it out of the boat). Boats are one of the few places to find undiscovered treasure with FE's. A good deal would be about 2K for a useable block, crank, caps and matched spacers combo. Good hunting!