Engine swap

[steelestandn]

I have a 79 merc 305. I was wanting to swap it with a 350. Does the year of the new motor matter? Will everything bolt up to say a mid 80's 350?

 

[TilliamWe]

Re: Engine swap

The small block chevy changed in about 1987 to a one piece rear main seal that uses a different flywheel than your 79. Also the center two intake manifold bolts are at a different angle than the rest. They also have center bolt down valve covers on them, where your have perimeter bolt down covers. So if you get into an engine like that, make sure you get the flywheel, starter, and intake manifold with it. Then of course the motor changed agian in 1996 to the "Vortec" which has a totally different intake manifold bolt pattern.
But if you bought a complete take out marine engine of any vintage, it would physically bolt into place, and even if you didn't get the front of the engine accessories, they would bolt right on. Best of luck.
(P.S. I know a guy in Florida that has a 1973 or 74ish block just lying around that needs would need to be bored out. He might sell it to you real cheap! he he)

 

[steelestandn]

Re: Engine swap

I was thinking of pulling one out of an old pick up.Is this possible? If so what would i need to do to make it boat worthy?

 

[oops!]

Re: Engine swap

hey steel welcome to i boats...

I was thinking of pulling one out of an old pick up.Is this possible? If so what would i need to do to make it boat worthy?

LOTS....!!!!!!

all elec is different....

you need a marine starter..../alt.../dist.../ flame arestor on the carb.

and thats just for starters...

lots of info on that here ..just hit search...

the stuff from the 305 might fit...

cheers
oops

 

[Haut Medoc]

Re: Engine swap

I was thinking of pulling one out of an old pick up.Is this possible? If so what would i need to do to make it boat worthy?

As long as it is pre 87, nothing......
You will need to transfer all of the accessories....
A truck cam is close enough to marine, so no problem there.....
Oh, you will need to change the core plugs to brass.....

 

[steelestandn]

Re: Engine swap

Sweet Thanks guys!

 

[steelestandn]

Re: Engine swap

By upgrading to the 350 will that mess up my outdrive gear ratio?

 

[erikgreen]

Re: Engine swap

No, it's the same gear ratio for the 305 and 350.

Just did this upgrade myself last summer, got a reman marine 350 and bolted on my 305 intake, with new alternator, starter, water pump, .....

One thing that might not be clear above though... if you get an engine that's around a pre 1985 or so, you should be ok, but if you get a newer engine you'll need to get more than the parts you have... the mentioned flywheel change means you need a newer flywheel cover, which mates to the outdrive inner plate, which mates to the outdrive bell housing.

So if you get an engine with the new flywheel size, plan on also getting a new flywheel cover, transom plate, and bell housing ($$).

If you can get a marine engine that's complete back to and including the transom parts, you'll be just fine. Otherwise, I'd go with a truck engine of similar vintage to your 305 and change the gaskets and freeze plugs.

Erik

 

[steelestandn]

Re: Engine swap

Is there a special marine head gasket that needs to be put on?

 

[TilliamWe]

Re: Engine swap

Some say yes, others so no. Fel Pro makes a graphite gasket that works well.

 

[mkast]

Re: Engine swap

The older style head gaskets had steel in them.
The new head gaskets are made of composite material.
Steel can rust, you know the rest.

 

[Gary H NC]

Re: Engine swap

Napa sells the marine head gaskets for SBC's...They are different than the auto ones...

 

[steelestandn]

Re: Engine swap

Thanks for the info guys.Im gonna get to work on the swap. I am so ready for spring!!!