Inboard/outboard marine v8 questions

[Snatch Napkin]

I am in the boating industry, but it has always been the electrical side of it. I have been messing with hot rods from the time I was 10 years old (22 years now).

However, I have yet to have mixed the two together. Now I am presented with a possible project to help a buddy out. My side of the boating business is in its slow period, so my shop is open to take on new tasks. Therefore, I would like to learn a little bit about what I might be getting into.

The boat that he is looking at is a 1989 Marlin ski boat. It has a 350 connected to an OMC inboard/outboard. The motor is supposedly locked up. We have not looked into it to be sure of what exactly happened.

My buddy has a running 350 that he can throw in there, but I'm not sure if it is a simple swap or what? I'm thinking we would need to swap cams, but what else?

What should he be looking for to be sure he isn't buying junk?

[shumpertdavid]

The cam, distributor, starter, flywheel, and exhaust mainly. The basic engine itself will be fine, but I would swap all the boat accessory over to the longblock. The way the marine engines operate are different from a car in the sense of rpm and load use. The camshaft and the distributor make the biggest difference there. Some motors run reverse rotation so you will need to make sure you have the correct water pump for the application.

[Aceman85turbo]

some of them run reverse rotation, check the spark plug wires to see the firing order. if its reverse rotation it is a much harder swap.

[Snatch Napkin]

Thanks. I had a suspicion of all of that, but no definitive knowledge.

[Snatch Napkin]

It sounds like we can handle this just fine. I've got an A-frame hoist that will straddle a boat trailer to pull the engine.

Are the OMC inboard/outboard setups decent?

Thanks guys.

[Rreemo]

It's not going to be a reverse rotation unless you are dealing with a twin screw setup, and it sounds like you aren't. All of the electrical accessory parts need to be USCG cert but I'm betting you can use all of the stuff off of the old engine for that. As indicated above, boat motors are setup for a much different powerband than what you'll find in a car and a lot of guys make that mistake by just throwing a car engine in and then find out it has no balls at all....biggest things on this are to make sure you have a marine grind cam in it (maybe the one in the old engine is reuable?)....and you also need to be sure and go with some healthy valve springs...remember boats typically see RPM sustained at higher rate for longer periods than cars do.

A friend of mine is a very good boat mechanic (posts out here sometimes actually), and he always told me the biggest things are cam, valve springs, don't over carb it, and you also want to make sure you have brass freeze plugs in a boat motor too.

I've done engine jobs in a few boats myself, and they really aren't too bad coming out and going in...sometimes you have to remove a bit of interior to access stuff, but it all goes back the same way it came out. While you are there be sure to replace the gimble (connects the engine to the outdrive)...it has a rubber dampner around the splined area that is bad about rotting and it's one of those things that's cheap while you are there.

OMC's aren't bad, but most people in the know on boats tend to prefer the Mercruiser leg...and of course Volve on the newer stuff. The OMC drive itself is a good unit IMO, but the way that they mount through the transom has a somewhat common tendency to cause some rot in the lower portion of the transom....that being said, I've owned 2 boats with OMC's myself and never had that problem. However my friend that owns a boat shop says that he repairs several OMC transoms every year. Best way to check that is to pickup on the outdrive and see if there is any flex or if you can hear popping, etc in the transom area while picking up on the drive.

Good luck! Post out here if you need help...I've done a bit with boats myself, but happen to know that there are at least 2 good boat mechanics on this board too.

[Snatch Napkin]

Excellent to hear! I feel even better about it now.