automotive 350 Converted to Marine 350

[zdawg_42]

I have looked hard and cannot find a complete answer so forgive me if I am re-posting a question. I am simply trying to find someone that has done or knows how to do a COMPLETE conversion from a Chevy 350 to a Marine 350. I have a 1989 OMC Cobra 5.7 with cracked water jackets-yea not winterized properly-but I need to find the most economical way to get it back on the water. I know you have to replace the soft plugs with brass plugs, I've heard problems with cams due to wet exhaust, I've heard you have to replace the head gaskets. Is there anything else? Some experienced help and advice would be greatly appreciated.

 

[Mkos1980]

Re: automotive 350 Converted to Marine 350

The SBC shortblock is identical besides the freeze plugs as you mentioned. For the long block, stainless headgaskets "should" be used esp in saltwater. If you know the vehicle the motor came out of we can usually see what cams in it and let you know if it'll be good or not. It wont be optimal but may not be bad eather. Differant engine mounted water pump is used. Has a brass impellor and is bidirectional.

 

[dan t.]

Re: automotive 350 Converted to Marine 350

head gaskets will only be an issue with raw water cooling,if you run a heat exchanger the stock gaskets are fine

 

[zdawg_42]

Re: automotive 350 Converted to Marine 350

So in theory I could take a long block out of a pickup throw in the brass plugs, change the head gasket to stainless steel, throw my carb, manifold, and bell housing off of my Cracked OMC cobra long block and cam would be fine...? I have heard many problems with the cams saying it needed to be changed out but...would that be everything required/recommended?

 

[Shrub88]

Re: automotive 350 Converted to Marine 350

My 260hp Mercruiser (Chevrolet 350) also had a dual roller timing chain. Trucks might have the same but some cars used a single roller or even nylon cam gears, I definitely wouldn't want that.

What year block are you getting?

 

[cr2k]

Re: automotive 350 Converted to Marine 350

Your big issue will be the camshaft. You are taking a smog cammed engine and using a non smog carb setup. If your old cam is good swap it out. If not call around and find the best cam for your engine. Also use the marine distributor as it is mechanical advance and SAE J1171 (spark proofed).

Circulation pump has brass or SS impeller with straight vanes not angled (to allow for bi-directional operation).

Another issue may be valve size. Just keep in mind a marine engine is not built to smog specs.

Head gaskets are SS for corrosion. soft plugs, I've seen both brass and steel in factory engines. I have replaced rusted steel ones.

Good luck, let us know how it works out.