I think we may have this answered but wanted to see if I could confirm the thought and maybe find a solution other than what I am thinking.
I have a 1999 5.7 Mercruiser Inboard. Last Sept took on a lot of water due to rough seas and the bilge going out and never knowing it until getting back to the dock. Everything ran fine. Replaced the cooling system in Nov and had several more fishing trips in Nov. Went back to the boat in Feb to do some maint and she would not start. Batts were low so I charged them. Still wouldn't turn over. Had the started checked and it was bad. Replaced starter and had good turn over but still no fire at all. Have checked the fuel, distributor, cap, coil, the plugs and wiring. There is good blue spark all the way to the plugs. I pull the plugs after attempting the start and they are dry. Tried pouring fuel in the carb and still no fire. Here is the interesting part...put hand over the carb and the air comes out, not in. Put finger over the PVC inlet and air rushes out after attempting the start and removing the finger due to lots of pressure. The exhaust flappers on the transom suck tight in while attempting the start.
After 10 plus hours of troubleshooting the thought is that most or all 16 valves only partially open and close due to some corrosion. I will do a compression test tomorrow.
Looking for thoughts or past experiences and hopefully a fix other than pulling the heads.
Thanks, JEC
I have a 1999 5.7 Mercruiser Inboard. Last Sept took on a lot of water due to rough seas and the bilge going out and never knowing it until getting back to the dock. Everything ran fine. Replaced the cooling system in Nov and had several more fishing trips in Nov. Went back to the boat in Feb to do some maint and she would not start. Batts were low so I charged them. Still wouldn't turn over. Had the started checked and it was bad. Replaced starter and had good turn over but still no fire at all. Have checked the fuel, distributor, cap, coil, the plugs and wiring. There is good blue spark all the way to the plugs. I pull the plugs after attempting the start and they are dry. Tried pouring fuel in the carb and still no fire. Here is the interesting part...put hand over the carb and the air comes out, not in. Put finger over the PVC inlet and air rushes out after attempting the start and removing the finger due to lots of pressure. The exhaust flappers on the transom suck tight in while attempting the start.
After 10 plus hours of troubleshooting the thought is that most or all 16 valves only partially open and close due to some corrosion. I will do a compression test tomorrow.
Looking for thoughts or past experiences and hopefully a fix other than pulling the heads.
Thanks, JEC
Be careful!!. I'd crank it with the plugs out to be sure, and probably change the oil. The seawater pump would've also been running backwards, so ingesdtion is unlikely, but any latent water near the exhaust manifolds may have found it's way in. The impeller may get messed up as it has now been flopped over the wrong direction, and now will be flopped back. If there was any hardness set, it may break a vane.