OMC 3.0 cobra exhaust manifold change

[wcasey5]

I've had high temperature issues since I bought this boat 3 years ago, it didn't run hot but it ran in the 180's or so. I changed the impeller, water pickup tube seals, water circulating pump. Then finally it overheated briefly and I removed the thermostat. It ran OK, but not great. But it didn't overheat which was good. I tried to clean it out which helped a little but then it just leaked where the riser connects. I finally bit the bullet and purchased a new manifold and riser from Michiganmotorz, what a huge difference. The engine runs cool and smooth, I think there was water getting into the exhaust and into the cylinders. She idles smooth and I'm very happy. This was a fairly easy job, I didn't disconnect any fuel lines or anything, I just left the carb dangle. Torqued the manifold down, heated it up and torqued again, and thats it. Highly recommended.

Here is what it looked like, looked great on the outside

 

[bruceb58]

Your manifold and riser actually look fine to me.

On your original manifold, did you replace both the manifold/to head gasket as well as the riser gasket?

Freshwater?

 

[wcasey5]

The riser looks fine, but inside enough had corroded away that the water was leaking out before the mixing part, and the bottom of the manifold was totally plugged. Wen I separated to upper and lower drive to change the water tube seals, there was a bunch of manifold corrosion in the drive that came out of the exhaust I run it in brackish water on the upper Chesapeake, near Baltimore. I replaced all the gaskets, and it went on like a dream.

 

[bruceb58]

That's good. The pictures definitely make it look better than it is then.