I know first hand what abuse a 330 will take. Run them wot until the belts burn off. The magnum have rectangle port heads and big heavier valves. You should add a valve job with new springs, valves and retainers to your list. If it doesn't have roller rockers yet you'll need to add them too. Early ones did not maybe non of them. 370's and up came with crane roller rockers. You can warm that 365 to near 500 with relative ease. Blower adds a whole other can of worms to the process. My suggestion is to have it set up on a dyno. Tuning a blower motor in the boat will be a job. One end of the spectrum its safe and too rich giving up power and the other end is insufficient fuel and it goes boom. Not to mention the added weight on the stern will effect handling. Plus if you add a blower you should add an intercooler too. I forget the exact numbers but its something like add 5 pounds and 200 degrees intake air temp and the net gain is 0.
Its a lot more fun to run a boat then it is to work on it.
Best of luck.
Currently: 4 vehicles and a boat have 24 tires on the ground in service (plus 5 spares), 51 quarts of oil in service to 46 cylinders connected to 32 gallons of diesel and 178 gallons of gasoline. Might be excessive exposure to maintenance.
Currently: 4 vehicles and a boat have 24 tires on the ground in service (plus 5 spares), 51 quarts of oil in service to 46 cylinders connected to 32 gallons of diesel and 178 gallons of gasoline. Might be excessive exposure to maintenance.