What all needs to be changed to convert auto motor to marine

Brass f\Freeze Plugs, Stainless Steel Head Gaskets, Marine Water Pump - (has brass impeller), and Water Cooled Exhaust Manifolds I believe are the main parts, if you truly want a good marine motor replace the exhaust valves with inconel

Cliff

You'll need a cam change and depending which engine you have maybe more to make it live in a marine application .

I addition to all the GOOD answers above...a marine starter, distributor and alternator. The distributor for a car has a different advance curve than that of a boat and the starter as well as the alternator should be USCG approved for spark resistance plus the fact that they are designed to be used in a severe marine environment.

Thanks for all the info u guys are alot of help

Do the auto part store carry some of this or just better buying from a boat store any suggestions

Oreilly can get stuff from sierra marine, and Wilson (starters and alternators) that should cover most everything you need. id it a common engine? American V8?

Napa also has some of the parts. What engine are you converting?

Would be building a Chevy 454 possibly

Marine engines and car engines are different internally . All if the clearances are different for marine application. Rod and main bearing clearance is larger for marine use. Also piston to wall and ring end gap are different . It makes a big difference if you want an engine to live in a marine application .