Bill is absolutely correct, I sure don’t want you to be ripping that thing to pieces for no reason. And I agree, please do NOT remove that exhaust cover….Don’t take the chance of snapping off hardware…Again, the water travels through the exhaust cover first before getting to that thermostat cavity, so a blockage there seems very unlikely. Yes, perhaps an exhaust leak is mixing with the water stopping the flow, but that doesn’t seem very likely either (when I say exhaust leak here, I am referring to an exhaust leak in the inner exhaust cover the water pump is a different matter), especially with the SS inner exhaust cover. In any event, that would be my “last guess” at this point. You removed the cylinder head, the cylinders sure look good, hard to believe that was in salt water. But, it is important to examine the cylinder head now, especially the passages where the water enters the thermostat pocket. Please don’t “reuse” the head gasket, that is just asking for trouble…Yeah, it is OK, to reuse it temporarily for testing surfaces, but plan on replacing it once the issue is resolved. Be sure to grease up the threads on all the bolts prior to final assembly.
You mentioned some sort of prior electrical issue on the boat, which has been resolved/removed…That could have been the cause of the electrolysis damage to the gearcase. And yes, the paint could have simply fallen off the block leaving that red colored lyfanite coating. Look at the round ID plug on the gearcase, the block is original if the serial number matches the ID tag on top of the swivel bracket.
OK, so back to trying to look at that gearcase. You mentioned the water pump is in place, you may have to remove the impeller housing again in order to have a closer look at the water passage from the intake up to the pump. I’m hoping you did not use any sealer between the aluminum impeller housing and the SS plate anyway, you can probably leave the SS plate in place, which is what you sealed up. Post a few pictures of the inside of the impeller housing, perhaps we can see something there. Post a picture of the top of the SS plate as well.
But again, it is very important to consider what Bill is saying, these engines do not like to cool properly when run in a test tank…..
It sounds like you are trying to use some alternate gearcase in an effort to test, this doesn’t sound like a good idea….Like everyone has said, although the internals are very similar, the bolt patterns are different, and the water pump is different as well. Let’s skip this for now, an expensive and time consuming project, that may just create more confusion than good answers…
