Need manifold for Gray Marine 4-112 engine

[allen]

When I removed the water inlet fitting to clear a bad clog half the threads on my Gray Marine 4-112 manifold broke off. That left only the back half of the threads still there. I used Marine-Tex and that got me home from the boatyard where the clog happened. Dave Van Ness can't give me a date on when or even if he will have a replacement. Everyone else refers me to him.

Anyone know where I can get a used manifold?

[rcvesselstyn]

With the high cost of exhaust manifolds you may want to consider just having it retapped.

[allen]

I will certainly try that if the epoxy fails before I can get another manifold. I think the epoxy will last forever but nobody else does.

[allen]

The epoxy I used on the water inlet has held fine all these years but today water started exiting just below the exhaust flange. Something also caused the engine to quit and although it turned over freely, it would not restart. We were close to our slip at the time and managed to get her put to bed with minor damage from contacting a boat that was sticking out of the slip by 2 feet.

The conclusion is that the manifold is shot. If I can't find a solution, the engine is going to have to be replaced with something.

Anyone have any ideas? I have not pulled the manifold out yet but as I reached down to feel where the hole was, pieces of rusted manifold came off. Not good.

We were the only boat out sailing today on SF Bay that we could see. The rain stopped as soon as I stepped foot on the boat. Plenty of wind.

[allen]

VanNess found a manifold and offered it to me for $750 so I guess I am set. The old one had a hole in the exhaust header from cylinder 4. I am assuming that leaked the pressure needed for the water lift to eject the water at the slow idle I was using at the time the engine quit and water backed up into the engine. I need to answer this question to know the problem will not repeat. I really don't know enough to say that a hole like this could leak all the pressure.

PXL_20240111_201858518.jpg (200.51 KiB) Viewed 2291 times

[rcvesselstyn]

Wow! Your scenario sounds logical to me. However this would mean when the engine was running you would get a lot of noise and a lot of exhaust smell in the area of the engine. It would have been extremely unpleasant to be below when the engine was running. If that was the case, then I agree that probably was the problem. Definitely not what I would have expected during our conversation about the valves. Glad you were able to find a replacement exhaust manifold. I can remember we had a Chrysler Royal( Flathead straight 8 cylinder). We epoxied that manifold for a few years before it was toast. That was in 72' and the engine hadn't been made since the 41'. Looking back that was only 30 years but it was extremely hard to find parts, or even anyone who knew anything about the engine. We finally found a functional exhaust manifold in a boat wrecking yard. Good luck!

[Kurt]

Take it to a good machine shop or motor block welder. You will need to remove it of course, but it sounds like this is a good time for a thorough inspection. could also be time to re power. Im running an electric in my Cal 2 29 past 10 years...Love it!