ok so sence my engine goes in a closed compartment with sun deck that goes over engine i need to use all marine stuff?
To be Coast Guard legal (not to mention safe), I would make sure everything is Marine SAE approved.
The list is endless.....
Solenoids, relays, alternators, starters, distributors, chokes (elec.), fuel pumps, carburetors, hose, flame arrestor/air filter, bilge blower, bilge pump, battery enclosure.....
There are literally hundreds upon hundreds of Marine rated products and all should be researched thoroughly to be sure you wont have an event, that is if you are trying to create a marine engine from scratch...
Most engines built by a reputable supplier (ie. Marine Power, Mercruiser, Indmar, and so on) already have the necessary components on them and should be legal, but if buying used, everything should be verified....
Gaskets are a longevity thing, has literally nothing to do with safety, same goes for freeze plugs. FWIW if a freeze plug fails on a jet boat and there is no way to shut the water off from the jet pump, she sinks to the bottom....

Do the homework like you have already started and you will be fine.

GT