Boomyal??? Need help with bad OMC 351W!

[mike.devincentis]

I was told to contact you with my problem as you might be able to shed some light on the subject.<br /><br />I have a 90 Chris Craft with an OMC 5.8, which is the 351 windsor. It is latched to an OMC rear end. I bought this boat about 4 years ago and after running it one summer, started to notice water mixing with the oil. Long story short, after many months of diagnosing, I pulled the engine to find that there was a 16 inch crack on the underside where the crank is, next to the cylinder walls. It must have froze before I bought it.<br /><br />Anyway, I am looking for a new, inexpensive engine to replace this one. I have seen the remans at Rapido Marine, but that is kinda pricey for me now at $1,400.00.<br /><br />My question for you is this. Can I use a block from a truck, rebuild it myself and put the same cam, crank, and whatever else right onto it or do I HAVE to find a 'marine' grade engine block to replace it. What parts would I 'NEED' to reuse from the original like the cam?<br /><br />Also, will a 302 work in my boat? I know I can use the same heads, but I would have to get another intake, and probably different exhaust manifolds. Also, would it fit in the same engine mounts on the boat and would it fit up to the rear end? Has anyone ever swapped out a 302 for a 351? What would that do with my power if I put the 351 heads on a 302? <br /><br />I know a guy that has an 88 Ford Van, Econoline that has a 302 in it. He wants $400.00 for the whole thing. If I could use the 302, this would be more like my price range because I could do most of the work myself and save money.<br /><br />I am looking to get back on the water with as little out of pocket as possible. I plan on keeping the boat for as long as possible, as there is nothing wrong with the shell.<br /><br />Any info would be great.<br /><br />Mike

 

[rbezdon]

Re: Boomyal??? Need help with bad OMC 351W!

Try these guys. They were $1100 for a remanufactuered long block Chevy 350 4 bolt main with no core exchange. It cost $150 to ship it from Texas to Chicago.<br /><br /> http://www.tbolt.net/marineengines.htm

 

[JasonB]

Re: Boomyal??? Need help with bad OMC 351W!

The 302 would use the same exhast manifolds, but you are correct, the intake is different.<br /><br />I wouldn't downgrade to the 302. The 302 is a great motor, but the 351 makes more torque. Unless you build the 302 up, you may be dissappointed in the power, however, it would be a direct bolt-in. Your other accessories should work fine. The carb on the 351 may be a bit much for the 302, but doubtful. The 302 is 80-100lbs lighter than the 351 and about 2" narrower and 2" less height if memory serves. The 302's that mercruiser used often came with 351 heads, mine did.<br /><br />I would R&R your 351. The block from a truck should work fine as long as you replace the freeze plugs with brass ones. All your other items would bolt on/in. Since you would be rebuilding, I would probably replace all bearings and likely the cam so its fresh, and if you selecet a good one, youmay pick up some power.<br /><br />My Mercruiser 302's casting #'s indicate it was cast for a Lincoln Continental....

 

[mike.devincentis]

Re: Boomyal??? Need help with bad OMC 351W!

Thanks for the replies.<br /><br />JasonB,<br />I have been told the 302 would run better with the 351 heads but I know I would loose the torque I used to have and I am not sure if I want to do that. It is a 21' boat and I like to load it up with people and go skiing, knee boarding and wake boarding. Got to have the whole shot to get up on plane. <br /><br />When you say R&R, what do you mean? <br /><br />vatter41,<br />Thanks, I will check out that web site. <br /><br />Could I not use the same cam that came from the original with new lifters and new pushrods? In another post, someone told me I could.<br /><br />Where is Boomyal?<br /><br />Thanks again,<br />Mike

 

[JasonB]

Re: Boomyal??? Need help with bad OMC 351W!

Repair or Replace.<br /><br />I have a 302 in a deep V 19' and it shoves it to near 50mph with a 2bbl carb. With a '21, I would be hard presses to give up the extra torque and your boat probably won't notice the extra weight. As for the cam/lifters/rods, I reused my pushrods as they were in good shape, but I replaced the lifters and can (the new cam was purchased as a matching set that included lifters and springs). The old cam was possibly ok, but as I was doing a complete rebuild and upgrade, I went with new.<br /><br />351's are about as plentiful as 302's.<br /><br />Boom will be around before long.

 

[Boomyal]

Re: Boomyal??? Need help with bad OMC 351W!

Mike, I'd stick with the 351 truck engine. All of your brackets pulleys, distrib., oil pan etc would fit right on. Alot of those items would not fit a 302. The cam from a carburated truck engine would probably be ok, but if it came from an auto you would want to change the cam. You can also use a later roller cam fuel injected 351 engine. You would definitely have to change the cam on that one as well as swap your intake manifold.<br /><br />Also you want to pay particular attention to the front timing cover as your marine one is iron and auto units are aluminum so you'd probably want to swap it out from your current engine. Plus some auto/truck 351's may use a different direction water pump depending on the year etc. Be sure to put a new timing chain set on it.<br /><br />Your current 351 marine distrib would not fit a 302 nor would your oil pan if your new motor did not have the right config. All things add up to getting a 351 replacement for best economy.<br /><br />As noted you'll want to replace all freeze plugs with brass. Steel will not hold up very long without using antifreeze.

 

[mike.devincentis]

Re: Boomyal??? Need help with bad OMC 351W!

Boomyal,<br /><br />Thanks for the response. I think I will stick with the 351. Never know when I will need the additional torque. <br /><br />Could I not use the same cam that I have now from my old engine?<br /><br />What would be involved with making the engine fuel injected? I know I would need another intake, but what about other parts? Is it possible or even worth it? What would it do for me? I could pull an engine from an old late model ford truck and use that, right?<br /><br />Thanks for all the help.<br /><br />Mike

 

[Boomyal]

Re: Boomyal??? Need help with bad OMC 351W!

No reason you can't use your existing cam. Just be sure to keep your lifters in order when you pull them out. <br /><br />Fuel injection would be nice if you have the near 2 grand to pony up for a Holley Marine TBI FI system.

 

[mike.devincentis]

Re: Boomyal??? Need help with bad OMC 351W!

Uh, no.<br /><br />I think I will wait on that one.<br /><br /> <br /><br />Great, if I have any more questions, I will let you know.<br /><br />Thanks again,<br /><br />Mike

 

[Boomyal]

Re: Boomyal??? Need help with bad OMC 351W!

Now that you know what direction to take, get to work before summer is over.

 

[mike.devincentis]

Re: Boomyal??? Need help with bad OMC 351W!

Thanks a lot for your help. <br /><br />I wish this forum had PM's so we could message people privately.<br /><br />Mike

 

[KaGee]

Re: Boomyal??? Need help with bad OMC 351W!

Originally posted by mike.devincentis:<br /> I wish this forum had PM's so we could message people privately.<br />

Yes, that would be nice... but this is a free forum after all.