Can I replace 88' OMC v6 with Remanufactured GM 262 Vortec

I have an 88' OMC cobra with 262 V6 2BBL Rochester Carb that was improperly winterized and now has a cracked block from beneath the pushrods to the cooling jacket. I patched the crack with high temp JB Weld and reassembled the engine. After running and timing the engine to 6 BTDC it ran hot in the exhaust and specifically more on one side than the other. Did a compression test and got zero pounds on cylinder 5. Im now looking to replace the engine with a re-manufactured GM 262 with the vortec technology as an upgrade with a new marine intake manifold to fit my carburetor and thermostat. will the year gap when these engines were released fit my old setup. The research Ive done it looks like it should but i have limited experience with the difference between models.

 

Welcome to the forum.

The block on the two V-6's are the same, the heads are different, as are the intake and possibly the coolant flow, but should be an easy fix, though I'd have to look it up on the 262 Vortec.

 

The new engines have the counterbalance shaft. They are much smoother.

 

Does anyone know whether or not the 97-91 one piece exhaust manifolds will fit over the new vortec valve head covers? Its a tight fit now with the stock head but I know that the exhuast for that model i.e. the Volvo Penta exhaust manifolds are a two part vertical manifold vice the one piece curved with the older style.

 

I'm fairly sure the new LV3 engine is completely different (5th gen LT1 variant), but previous 262's are also a bit convoluted. In 1991 they were still using the 90° LU2 engine (1991 - 1992 only), which was an upgraded LB4, but in 1992, they moved to the L35 and significant differences came along (first of the balance shaft models). My understanding is all the balance shaft engines have mostly interchangeable parts, though the very last of this engine family production run, do have different heads (still bolt on), but oil pan issues can crop up. If you can use the previous oil pan or the new one will clear your application, then not a worry. The biggest change was in 1996, with internal reinforcement, moving freeze plugs, timing cover changes, etc. The real trick when matching up these engines is to match up the actual engine model. I think you have the L35 variant, so look for one of these, after verifying this is actually what it is. One way is to look up the number, but a quick check is the intake and if it has little curved lips to clear the injectors, it's the L35. If not, it's one of the earlier versions. The manifolds may or may not fit, cross check the application numbers at Volvo, to see if they do.

 

I believe there are three different shapes for the exhaust ports. You should check by gasket application to the head casting number.

 

Thanks for all the support! The setup im interested in comes with new intake manifold with 4bbl carburetor, an electric fuel pump, and a new bracket for the carb to match the 8 bolt fasteners on newer Vortec intakes. I have seen some pictures online and was told from this specific shop that the one piece exhaust manifolds would fit which would make figuring out the exhaust conversion simpler. The new setup comes with a new oil pan because the post vortec doesnt have the same drum style pan like older models. The newer carburetor and fuel pump though do require power which wasn't required on the older model. Should I supply power directly from battery connection to the starter via inline fuses for the electric choke and fuel pump? lastly are the engine couplers standard for newer models. The bolt holes in pictures ive found seem to fit my coupler but I only have pictures to check.

 

The electric pump needs a shut-off switch that runs off oil pressure for safety and to comply with the law. It prevents the fuel pump from running if the engine is stopped.