standard ACX plywood is fine. for the double-thickness, use tite-bond III to glue two pieces of 3/4" together.
Rustoleum is fine. use a hardener. I believe that is link 18 or 19 in the sticky
I would also suggest going thru the forum stickies. specifically the 3rd down. https://forums.iboats.com/threads/how-tos-and-other-great-information.283508/
go thru threads 14, 15, 18, 2, 3, 4a, and 4b in their entirety.
welcome aboard. the standard exterior grade plywood lasted over 35 years. I would suggest another piece of plywood. youre looking at a saturday, or a weekend at most,
its a mid 80's OMC brand. so the build quality was garbage. most rotted and fell apart in the 90s
the maximum life expectancy of a boat designed in the 80's is about 15 years without major work.
Welcome aboard.
Just as an FYI, your free boat will be extremely expensive to get it operational.
the motor is the cheapest part of fixing the boat. the old OMC brands such as the boat you have there were not known for great build quality. expect to pour about $5k into the hull
before you...
buy a rotten mid-late 90's bayliner and get the whole post 1991 3.0 with the upgraded 1992 and later Gen 2 drive. if you do it right, you buy the whole thing for $500, pull the motor/trans/controls and then sell the trailer and some parts for the $500. then you are only out the hull disposal fees.
by a little hot, a 10 degree rise in temperature can cause the iron head on the open deck aluminum block to spit the head gasket.
so keep on top of the cooling system, especially the raw water pump.
the benefit of hydraulic jack plates is that you can adjust from the helm. used a lot on flats boats, etc. allows the motor to be lowered to bite on holeshot, and raised plane, and then really raised up to go in/out of skinny water at idle speed. by lock in place, that is what the check...
If the 383 was built for a truck or boat (build for torque, with proper quench and a good low-overlap cam). No problem. Just swap the core plugs to brass, swap the head gaskets to marine swap the water pump to marine.
Use a marine carb, ignition, front accessories and rotating electrics...
Pull your drive (you have to anyway to check alignment and gimbal bearing).
You're going to be replacing the raw water pump and it looks like at least a seal or two
The hole is a drain for the exhaust cavity
