Broken exhaust water gate - Maxum Boat Owners Club

case1 · 04-28-2019, 08:23 PM

Took off exhaust manifolds and risers for inspection and found one of the exhaust flappers broken, half missing. Replacing it doesn't seem to be difficult, but should I be looking for the missing piece? After removing the flapper I looked down the y pipe and couldn't see anything.

mmwjr · 04-28-2019, 10:21 PM

Some times it goes past the y-pipe and gets stuck in the exhaust bellows before the shift shaft rod. Then again they can travel all the way through the system.

jrsick · 04-28-2019, 11:55 PM

I lost both sets of exhaust shutters last year. I found two of the four pieces lodged in the exhaust bellows behind the shift shaft. I had to remove the lower unit and look up the exhaust to find them. I never found the other two.
You may want to tap on your exhaust bellows, or look down your prop.
The only way they would cause a problem is if they restrict exhaust. You would notice this at higher rpms. If your engine is less responsive over 3000 rpm or so, it could be your exhaust shutters.

case1 · 04-29-2019, 12:50 AM

I'll get a scope and look down the y pipe to see if I can find it. Maybe I can grab it?
I have bravo II stern drives and haven't taken them off yet, not sure how difficult of a project that is?
98 3000 SCR twin Mercruiser 5.0

case1 · 04-29-2019, 01:11 AM

Last season I had a problem with starboard engine after About an hour of running at full load engine backfired and stalled it would restart but couldn't rev higher than 2000 Rpm. I would change fuel filter when I got to port and it would run fine but after an hour it would do it again. Changed fuel filter several times but never found debri or water.
The broken exhaust flap is on the port engine.

mmwjr · 04-29-2019, 01:20 AM

Being Bravos there is no shift shaft in the exhaust passage to catch a broken flapper and they most likely went overboard. If changing the fuel filter temporarily let the starboard engine run better it must have getting clogged with debris or water. If this is still happening try getting some gas line and crisscross what engine the tanks are feeding to see if the issue follows the starboard tank.