lets not. its been rehashed to death. however for some reason the search function isn't pulling up the past lists.
assuming you have all the updates done over the years...... larger heat exchanger, exhaust elbow change, etc.
so much easier and cheaper to pull the motor and drop in a proper motor that has support. unless you have twins closer together than 34" then you are stuck with the platypus motors
issue #1, aluminum block and iron head. only an engineer that went out for lunch and smoked peyote then listened to the accountants would do this. dumb as dumb could be. solution - edelbrock aluminum head (ford FE motor - 460)
issue #2, the open deck or floating bores. cylinder bores need to be stabilized. usually results in some minor machining and a 7 gauge laser cut "spider" is welded in the top of the deck to keep the bores from moving around
issue #3 the charging system. both the anemic charge coil in the front damper and the required water cooled regulator. these are outboard parts. Mercury Marine used these because they were cheep. 'nuff said
issue #4, 5, 6, 7 - using a rubber raw water impeller as the cooling water circulating pump. rubber not intended to run that hot. using a custom made cam without heat treating the cam drive stud was simply stupid. relying on cheap seals to keep oil and coolant from mixing. most peiole putting a scew in the weep hole because they thought they "fixed it" seriously, there should have been a real waterpump
issue #8 - motor is half the pistons and rods from a Ford 460 with a GM patterned flywheel and a GM like timing setup all while connected to a custom mercruiser crankshaft. this means you are stuck with the stock grinds for the cams for a boat
now, these motors have been used in various hotrods and these are the fixes for the shortcomings in a car (most can be used in a boat).
aluminum head with some modification is easy (boat friendly)
the open deck fix is a bit more difficult unless you have access to a 5000 watt laser or larger and a machine shop.(boat friendly fix)
with a bit of work, a new front damper can be had. and if you want, an alternator can be fitted. (alternator conversions are common in boats. no need for the damper change unless your racing)
a bit of welding, an electric water pump from either Mezzier or davis craig can be used for a circulating pump. especially when re-routing the cooling lines, etc. (this is a hot-rod only mod)
there are a few hot-rod cam grinders that can make a decent cam. (again, not needed in a boat)
normally these motors end up with a custom header and custom intake.
by the time you take the motor out, and fix all the items that need fixing, a 4.3 would have been installed and you could have been back on the water for much much much less time and water. unless your boat has twins closer together than 34"