Pull the plugs
When we pull the plugs, all appears to be good with the plugs. The Engine is running rich but not a single plug that looks steam cleaned or new, which is a good sign for valves and the cylinder walls. It also appears there is not a head gasket failure or water intrusion into the cylinder that way. It also means that there is a good possibility there is a crack in the lifter valley or water intrusion into the crankcase from some other means. I’m still going to do the leak down test. I also found the firing order for the engine, so I know what wire goes to what plug.
https://www.shopsbt.com/I verified as I removed each plug that it corresponded to the correct location on the distributer. Yes it a Chevy/GM , even though Sea Ray has a MerCruiser 5.0. This is an Alpha Drive too. My research seems to indicate that the motor is a 2006 /2007 305 GM Vortec. The main difference is the Camshaft duration & lift, the intake and exhaust manifolds. This is a Multiport fuel injected motor and the intake seems to be a MerCruiser/Mercury specific item. It seems to be a thousand dollar part. Nothing I’m going to find this at SBT (Short Block Technologies), where I get most of my parts for me Sea Doo’s. I think that I’m going to spend some time chasing parts.
What is next ?
Now that we have pulled all the plugs, and not found anything definitive. We have made some assumptions about what we see here. What we do know is that there is a lot of water in the oil and that the plugs are good. As the step as part of our troubleshooting process we should do a leak down test.