OMC 3.0 engine cracked manifold, rebuild + power increase?

[Wellarmedlamb]

1988 OMC Cobra 3.0 in a sunbird 19' open bow. Picked up this boat for next to nothing. Owner said maybe a cracked block. Someone had torn the engine apart in the boat and the cylinders were full of water. We got the pistons freed up, re-assembled, new coil, plugs, plug wires and points/condenser. Fired right up. It knocks, sounds to me like a wrist pin knock. Also, with the front cooling hose(on the manifold) unhooked I could smell exhaust/gas fumes and could feel pulsing in that hose(only ran it for about 30 seconds). My theory is that they got a hole in the manifold, filled a cylinder with water and then hydrolocked a piston, shearing a wrist pin. Assuming I find a hole in the manifold I will want to rebuild the engine boring .030 due to cylinder wall gouges. Can I do anything while I'm in there to increase power? Roller rockers, cam, compression increase? I was thinking V6 swap but the search function convinced me otherwise. Am I wrong about swapping being overly expensive and time consuming? Thanks!

 

[Howard Sterndrive]

there is no additional power to be found from a 3.0. Just get another 3.0 and be happy with the 130HP, or go to a V6. The swap is time consuming and expensive (your existing outdrive only good for the engine you have now - so you'll need a different drive) and if your boat has less than a 25 or 30 gallon fuel tank, you'll never be happy with the range.
You'll need a dressed V6, mounts for the front fabricated, A Y pipe, an outdrive with correct gearing- maybe power steering if your 3.0 isn't ps equipped. etc. etc.

You could probably throw that boat away and find a V6 powered one for same or less than the cost of swapping. The hull is worth very little in 1980's boats.

 

[Bondo]

1988 OMC Cobra 3.0 in a sunbird 19' open bow. Picked up this boat for next to nothing. Owner said maybe a cracked block. Someone had torn the engine apart in the boat and the cylinders were full of water. We got the pistons freed up, re-assembled, new coil, plugs, plug wires and points/condenser. Fired right up. It knocks, sounds to me like a wrist pin knock. Also, with the front cooling hose(on the manifold) unhooked I could smell exhaust/gas fumes and could feel pulsing in that hose(only ran it for about 30 seconds). My theory is that they got a hole in the manifold, filled a cylinder with water and then hydrolocked a piston, shearing a wrist pin. Assuming I find a hole in the manifold I will want to rebuild the engine boring .030 due to cylinder wall gouges. Can I do anything while I'm in there to increase power? Roller rockers, cam, compression increase? I was thinking V6 swap but the search function convinced me otherwise. Am I wrong about swapping being overly expensive and time consuming? Thanks!

Ayuh,.... Harvest any Value you can find in it, 'n then go find Another boat to build,....

The prospect of you buildin' a reliable boat out a 1988 sunbird with a blown motor, for a reasonable price, just Ain't in the numbers,....

 

[Wellarmedlamb]

Thanks guys, I was afraid that's what you were you were going to say.