I think this may be a separate issue, but I didn't quite
understand the cooling configuration, so it may be related to my "water in oil".
This replacement engine for my "cracked block" motor is from a salvager. The replacement engine has a strange cooling setup that "achris" identified as a "reverse flow setup" (a good thing). I was trying to understand the flow path, and was quite confused. Now I find out that for the "reverse flow" to work, a "water block off plate" is required between the manifold and riser to direct the raw cooling water in the right direction. Instead of a direct connection from the water re-circulation pump to the bow end of the manifold, the hose goes to the stern end of the manifold and enters at the end cap (re-fitted with an elbow on the cap like at the bow end). I couldn't figure out how the cooling water was forced in the right direction. Since this "replacement engine" had the riser removed (due to rusting) and I didn't realize that there needed to be a double gasket and water block off plate on the riser. It looks like Barr makes a plate with a bleed hole so air doesn't get stuck under the riser.
I found MC-20-60207,
View attachment 349617
There isn't much information on the "reverse flow setup", but it looks like this part is definitely required, with a gasket underneath and on top of the plate between the manifold and riser. Is there anything else I am missing? I couldn't find a "parts list" that showed what items were in the "reverse flow kit" from Mercruiser. Evidently the kit was offered AFTER production ended on the 165, as an attempt to address uneven cooling, or hot spots in the manifold.
The riser on the "replacement engine" is definitely kerflunken. I put a garden hose in one of the "plugs" on the riser (where my reverse flow elbow would screw in) and I saw water come up to the slots at the manifold/riser interface, but also saw water bubbling up through the exhaust side of the riser. At first I thought that was how the return water exited, but I finally saw the two slots on the round part of the riser that connects to the rubber bellows. The water bubbling up was definitely through a rusted hole between the water jacket and exhaust side that wasn't supposed to be there.
The riser from my "cracked block engine" appears to be in much better shape. I haven't done an "acetone" test yet (need to get into town and get some supplies), but I did see water flowing through the "plug hole" and then through the proper slots on the end round part of the riser. I let the riser sit all day and did not see any water level decrease, or any wetness on the exhaust side. I'm hoping the riser might be okay for now, but will definitely do the "acetone test" very soon.
Anyway, when I ran the engine I had the better riser installed, but with a "regular gasket" - not with the block off plate. I don't see how that could have allowed water to get in the oil, but as I said, I was quite confused with the flow path.
Is there any way that running without the block off plate might have caused the water in the oil?
I guess my next step will be to unbolt the manifold and do an "acetone test" on the manifold and riser.
Any other ideas/suggestions for next steps?
When run in saltwater, are the manifold and riser "maintenance replacement" items after a certain number of years?
