I'm kinda building a new motor for my 27 Ford along the same lines as you are, except I decided to go with a 331 stroker kit instead of a 347. If you were simply wanting to do a mild build at the 306 CI size I would say you are going to be ok with the engine you are starting with. But I wouldn't spend the kind of money you are going to have to put into this engine starting with a 1972 Ford marine engine.

You say you are new to this...........we all were at one time, so let me give you some advice if I can. Marine engines always scare me for a buildup. The reason is salt water. Unless the engine was fresh water cooled or run in only fresh water it has seen a whole bunch of corrosion inside the block in the past 37 years. A friend of mine rebuilt a 350 Chevy boat engine and when he was all done one on the cylinder sleeves rusted right through, he had to scrap it and start over.

Secondly, there are so many good late model 302 blocks around that they make so much more sense to build. From 86 up they are already roller cam engines so you can slide in a Motorsport or other cam and be way ahead of what that 1972 engine would give you. You say you cleaned up the rust but that is no basis to build a 347 stroker on. The block should be tested, and then line bored, decked, overbored or honed again, hot tanked, new cam bearings and freeze plugs. The work I outlined will cost somewhere in the neighborhood of $ 700 to $ 800 generally. Then the stroker kit will cost you $ 1000.00 minimum, and you haven't even started to buy the cam kit, do a valve job, or add all the other parts like intake, carb, timing set, etc.

Please understand I am not trying to discourage you, but I think it would be a real mistake to start dumping serious money into a 37 year old boat motor when there are so many better engines to start with. Maybe what you should do is clean up the internals of the engine you have, do a ring and bearing overhaul, and get it running. Use it until you can build the stroker you want. To do what you outlined is going to cost you $ 4000.00 minimum, probably more.

Good luck with whatever you decide.

Don