4.3 OMC exhaust manifold swap?

[xdgt03]

I have a 1990 Four Winns with a 4.3L OMC and the exhaust manifolds have both been welded from what I assume were cracks from failing to winterize. I bought it this way.

The motor is fine and runs perfect. There is no water in the oil. The starboard side manifold is leaking just a little bit and the other is not leaking....yet.

I searched and searched because I thought I had read a thread about swapping the one piece manifolds for the 2 piece manifolds. Is there a kit that comes with everything you need to make it work or do you need to mess around with the tubes to get them to line up?

Any help and direction would be greatly appreciated.

Thanks, Scott

 

[HT32BSX115]

Re: 4.3 OMC exhaust manifold swap?

Hi Scott,

Is there a kit that comes with everything you need to make it work or do you need to mess around with the tubes to get them to line up?

Yes there is. And you NEED to replace those old "Bat-Wing" manifolds before they destroy your engine.

Here's one example http://marineengineparts.com/shopsite_sc/store/html/page370.html


Here's another from ebasic power.

There's several on the net. It won't be cheap but it'll be cheaper than a new engine!


Cheers,


Rick

 

[xdgt03]

Re: 4.3 OMC exhaust manifold swap?

Thanks Rick.

I have called a bunch or marine shops and found a few options. The cheapest I found was from a Guy in CA that fabs an elbow out of stainless with the split cast iron manifolds for $695 plus shipping.

I have another question though. All that is really needed is just an elbow and a coupler. Does anyone know if there is a place where you can order generic cast iron elbows? I can get a new split manifold kit for $500 shipped but that has the outlet running straight the back. Seems like fabbing one myself should be too difficult.

Is part of the reason not to use say standard stainless exhaust pipe the fact that it gets too hot and will melt the coupler? I think the guy in CA makes his from a thick walled stainless. At least it looked much thicker than standard automotive pipe.

Thanks, Scott

 

[HT32BSX115]

Re: 4.3 OMC exhaust manifold swap?

Is part of the reason not to use say standard stainless exhaust pipe the fact that it gets too hot and will melt the coupler?

I'm not sure where you mean. The entire exhaust system (manifolds/risers) must be jacketed since the water must be completely separate from the exhaust gases to prevent any water from splashing/running back into open exhaust valves.

After that (past and below the riser) the exhaust gases and water are mixed intentionally to provide for cooling and some noise cancellation (if it's a thru hull).

The cheapest I found was from a Guy in CA that fabs an elbow out of stainless with the split cast iron manifolds for $695 plus shipping.

Those should also be jacketed SS risers. They work fine and do the same job as a cast riser. They're not all that cheap though for the ones I have found for my 454.