Omc cobra 4.3 engine block swap

[Carle3]

I am working on repairing my 90 Seaswirl Spyder Sport Omc Cobra 4.3 engine that has a cracked block. I have secured a 89 Chevy 4.3 out of a Sierra truck with a block casting of 10172756. I started to pull and disassemble my old motor and I noticed there are studs holding on my coupler and starting gear. The new block has bolts holding on the gear. My question is, is there more to tear apart or do I add studs to the new motor for bolting my coupler on?

 

[alldodge]

If your saying the mounting is different and your flywheel will not mount to the crankshaft, then the motor won't work.

Hey Scott Danforth thoughts

 

[Scott Danforth]

the coupler may have been studs and nuts, especially if its a button style that OMC used for a while that bolts to the crank BC

as far as the starter goes, should have been bolts from day one.

cranks and blocks should be the same between the two, so once the new 89 donor motor is stripped down to a short block, the core plugs changed and the head gaskets changed to marine, the marine water pump, marine manifolds, coupler, etc along with the marine accessory drive and marine electrics can be moved over.

 

[Scott Danforth]

doing digging, yes, cobras used a button style elastomeric coupler with studs. so buy a stud kit.

 

[Carle3]

Thanks Scott, as I was thinking this through last night that’s what I figured was just to add studs in place of the bolts. The pattern is the same. Someone brought up gaskets which brings me to another question, I was pulling my hair out trying to figures out what gasket kit to purchase. I was going to by a upper head gasket kit for an unbalanced 4.3 and individual gaskets as needed. Is there a better kit out there? I not rebuilding the motor.

 

[Scott Danforth]

Felpro marine gaskets for 1988-1991 4.3 V6

You need marine head gaskets

You also need a marine water circulating pump

Also, you need to change the steel core plugs to brass

You may not be rebuilding it, however you will need to tear it down to a short block, and build it back up

 

[Carle3]

So Far so good. I did install the Felpro Head Gasket Set and the Conversion Set. I replaced all the core plugs with brass transferred over my intake manifold, water pump and most other OMC specific parts. Pretty much just used the heads and block from the donor motor. All else has been swapped from my OMC motor. The one thing I am having to do is add an electric fuel pump. The new block is of a TBI build and has no accommodation for the mechanical fuel pump. I did check my lower shift cable since I have the outdrive off of the boat. That all seems good. Next step is reinstalling and aligning the motor. I do need to get an alignment tool yet.

 

[Scott Danforth]

Ebay has alignment tools for as low as $20