OMC ford 351 buildup question

[andrewmaeyaert]

"Hi,
I recently purchased a 1

"Hi,
I recently purchased a 1979 cobalt 18' bow rider (tri-hull)equipped with a ford 351 and a 800 series stringer. the previous owner cracked a cylinder head in the spring of 08. Then he let it sit all summer, and all winter with out winterizing it. So now, I believe I am dealing with a completely shot engine. I think this because when the he cracked the head, water got into the oil. so I think the internals are shot due to sitting water, also he did not winterize the engine, so I’ll bet the block is cracked.


Anyway... I decided to buy a mid 70's 351w out of an f-150 to use as a "core" to build off of. What I am wondering is will this work? Are there any differences in the truck block, and marine block? I would be putting all of the marine accessories on it such as alternator, and carburetor. I was also wondering how good the marine engines were built. i.e., how good are the intakes, cams, and heads. My plan was to mildly build up the engine before putting it back in the boat. (cam, intake...) my projected power output would be somewhere in the upper 200's to low 300's. Can the outdrive take that kind of power? I am new to the omc stringer drives, any info you might have to offer about these drives, or ford engines would help. Thanks for your time, and thanks for reading. I hope to here back form you soon."

 

[hystat]

"I think you will find that th

"I think you will find that the truck and marine long block (pan to heads) are identical. I wouldn't plan your build up yet

First, Get a starter on it and crank it and check compression and oil pressure (put a manual gauge in the oil gallery in place of the sender) and go from there.

Carburetion and intake on your OMC is already optimizing the power from the motor so just swap those over to the new engine after it checks out. Then replace the tin core plugs in the truck engine with brass marine ones.

250HP or so is all you will get out of a 351 in a boat because you can not rev it any more than 4600 rpm, and it is all you want as your 800 series drive is only good for 260HP.

p.s. - heads don't really just crack .. and the water in the oil was probably from the previous winter where the engine also wasn't winterized.

p.p.s. Do a very thorough insection of the hull and drive before putting money and time into this engine. 1979 was not a stellar version of the 800 drive. parts like shift cable and lower unit are no longer available new or used. Expect to need exhaust manifolds and risers as they will also be destroyed by freezing."

 

[andrewmaeyaert]

"the boat (hull, interior,

"the boat (hull, interior,...ect) are in excellent condition, and appear to be very well taken care of. the out drive is iffy. i haven't got a chance to check it out yet because the tilt motor is out, and the out drive is stuck in the up position. i did notice that the ball gears show some where. i do know that the boat shifts into, and out of gear. what else should i look for other than water in the oil?

also, i am aware that heads don't "just crack" the previous owner insisted that it was winterized every year except the last one?????"