Mikentucky
Member
- Jul 31, 2020
- 61
- Boat Info
- 1994 400 Express Cruiser, "Lollygagging"
- Engines
- twin inboard Mercruiser 7.4L Bluewater, straight drives
Straight inboards, so no flappers or shutter valves, just a water lift muffler that would normally let exhaust flow out without water backing up into the exhaust. But I'm thinking it was a "perfect storm" of conditions and operator error--I was backing upriver against a strong current. The port side was also against the dock floats, creating even more back pressure. With the exhaust opening underwater, all that extra pressure found somewhere to go, and doing it for about 15 seconds under those conditions ws more than enough to overwhelm the water lift muffler's capacity. And just being real, I think I made an error that was probably the final nail in the coffin Since I was focusing on positioning the boat and shutting down to refuel, I probably turned off the engines immediately without letting the mufflers, exhaust, and intake "clear" from the valve overlap....meaning as soon as I went to restart, I probably sucked just enough water backwards into the cylinder through the exhaust valves to do the damage.Fascinating pics, thanks for sharing! Are your exhaust flappers/shutter valves still intact and or in good shape? Maybe you had a small leak around the exterior of the flappers so water backed up with the continuous river pressure.