Jetboat cam

[squirtn20]

Anybody ever had an exhaust flapper suck in? (log manifolds, 3 1/2")

[jbone]

Never seen it, but I imagine it can happen when you stop after a long run. When the water in the engine and manigolfs cool, they take less space and if the seal is good on the flapper it could suck in.
Kinda like a tupperware container out of the microwave. When it starts to cool, the lid sucks in.
Just a thought.
J

[squirtn20]

Thanks
I've never had it happen before but it is a very tight seal. Long story short, today was the first day out with the "new" cam installed by my machine shop.

[SmokinLowriderSS]

I've never had it suck the flapper in, but pull it tight closed, yes. Rarely, but to lock it against the outlet has happened a few times I noticed.
Not running those small tips anymore so doesn't happen now.

[BDMar]

See it alot. It happens when the engine is turned off and there is a camshaft with a fair amount of overlap.... also if the engine rotates backward at all when the engine is turned off. It will fill the engine cylinders with water the next time you go to run it on the trailer and turn the water on without starting the engine immediately.

[squirtn20]

Thanks BDMar. Well heres my story. I swamped my boat last year at the dock due to a sudden storm. Not to much water in motor, but I pull it apart to see if a rebuld was needed. I took it to my machine guy (car guy, noy many jets in minnesota) he was supposed to measure and inspect everything and give me a call. I was going to do a cam change at this time so I wanted to know my old specs. Ooops he forgot. He cleaned up the block and heads and installed a "new" cam. A used cam from a boat "just" like mine that only had a few hours on it. By the time he called the scrap man picked up so the old one was gone. Wrong cam????