Ok coolant system aficionados I need some help.
At the end of last season I was having an overheating issue. After a number of failed attempts to resolve the issue I’m reaching out for some insight.
Here is what I have tried and what I know.
Replaced a few old and partially kinked hoses.
This model of OMC has a water hookup on the upper unit of the outdrive for running the engine out of water. When running the boat like that it wasn’t overheating to bad. And I was getting good stream out of the rear of the outdrive. I tried running it with the outdrive in a bucket and it over heated immediately. There was little to no stream out of the rear of the outdrive. So I thought maybe I had a blockage at the intake on the bottom of the outdrive. Nope…. Setup the garden hose at the intake and again I was getting good stream out of the rear of the outdrive. So I thought maybe the blockage was further in. Got back in the boat and realized that the issue appears to be isolated to the port side of the engine. So now I’m thinking it’s a blockage in the port side manifold???? I hoping that’s a way to confirm that without taking it off but I’m not sure how to do that. The coolant system setup is confusing and doesn’t look like anything I have seen before. I spent a ton of time looking for a diagram of the system but there is just nothing out there. I have the OMC book but Chris Craft had their own setup. The best I could do was find a picture of the same setup on another boat.
So if anyone could explain this system that would be great.
Here is a image of the engine and a diagram that I started to put together.
My plan as of right now is to remove both manifolds and use muriatic acid on them. Depending on how the openings look on the block I might remove the freeze plugs that I have access to and try to flush the block out. I’ve also been reading about products like Maritime descaler. I thought maybe that might be a better way to go. But again I wouldn’t know how to set it up without having the diagram.
Any input would be greatly appreciated.
...you changed the impeller? If your water hookup is to a hose w street pressure, it will push the water through. For drawing water up from the outdrive via the bucket though, if your impeller is compromised it can't generate sufficient suction.
If the impeller is old and you find it has "detonated" into pieces, it's important to retrieve any pieces that may lodge in the cooling system that create blockages and potential overheating issues.