Replacing 1985 3.0 with newer 5.7

[Jas0n]

I have a 20' project boat (well more of a hull right now) that I am replacing the stock 140 hp Mercruiser with a 1997 Vortec 350. Does anyone know if the flywheel housing will bolt up to the new engine ? I have worked at a GM dealer for 12 years and I remember that the trucks using the Iron dukes used the same transmission as the 350's. I know the 1997 Vortec motor requires a different flywheel as the mounting pattern is different and the newer sbc's are externally balanced. Is there a conversion kit available that includes the flywheel and coupler ? Or will my current coupler work ?




Jason

 

[incrediblened]

Re: Replacing 1985 3.0 with newer 5.7

If you're doing this kind of upgrade, it's going to be a huge advantage if you can find a boat that has a rotted floor / that's been wrecked / or that the interior is junk - but has a good drivetrain. That way you've got absolutely EVERYTHING that you'll need to install the new engine. (Outdrive, Prop, Engine mounts, Gimbal Housing, Transom Plate). Also, you'll be able to see how the floor is built-up to seat the engine mounts on the sides. (It mounts differently than a 140 merc).

 

[Bondo]

Re: Replacing 1985 3.0 with newer 5.7

Ayuh,... What Vintage is the 140hp(Not an Iron Duke, btw),..??
Alpha 1, or MC-1,..??

Ya know you'll need to replace the Outdrive, Right,..??
You'll need the exhaust Y-pipe that fits,...
Does the 140hp have a crankshaft mounted coupler, or flywheel mounted,..??

 

[Jas0n]

Re: Replacing 1985 3.0 with newer 5.7

It is a 1985 with a Alhpa 1.
Already planned on pairing to a 1.47 to 1 SEI drive.
I have the Y pipe and side engine mounts off of a 1986 (?) 350.

I am not sure about the engine coupling as my engine hoist is being borrowed atm.

 

[Jas0n]

Re: Replacing 1985 3.0 with newer 5.7

http://cgi.ebay.com/ebaymotors/86-9...r_Truck_Parts_Accessories&hash=item1e613d9ead


Is this the flywheel needed ? When I get to work in the morning I am going to see what my cost is on the GM #14088650

Would i be correct to assume that if I have the flywheel mounted coupler it can be reused ?

I did not realize untill 10 minutes ago that Mercruiser used manual trans flywheels, I thought they were marine specific.

What really sucks is I just threw one out last week after doing a clutch because it couldnt be machined. :facepalm:

 

[Jas0n]

Re: Replacing 1985 3.0 with newer 5.7

Old engine is out and it has a crank mounted coupler.

I belive the engine coupler I need is part no. 14505A2

Could anyone knowledgable confirm this ? and also the flywheel needed, will the one linked above work or do I need the
GM #14088650 ?

I think as long as the diameter and the tooth count are correct it will work as there isnt a clutch being bolted to it ??

Any info would be appreciated as I would like to set the block in place to get the front mounts in this weekend.

Also what capacity fuel tank ?? I think in the 40 to 50 range ?