Avoid suddenly closing the throttle?

[ricohman]

I have read a few threads about boaters suddenly closing the throttle and the engine injesting water through the exhaust.
I have a new 4.3 in my Islander 221 and I may have chopped throttle abruptly on an occasion or two but generally I try to slow smoothly for my passengers.
I am new to i/o's and I assume the water is being forced up through the exhaust. I have read about flappers but shouldn't these stop the water from getting past?

 

[Don S]

Re: Avoid suddenly closing the throttle?

It's not a problem chopping the throttle, as long as the engine is still running. The exhaust keeps water from entering the exhaust system up to the elbows. The problem occures when you chop the throttle and shut off the engine. No exhaust to keep the wake from pushing up the exhaust tube. The flappers (aka shutters) should prevent MOST of it if they are working.

 

[ricohman]

Re: Avoid suddenly closing the throttle?

OK. I don't know why you would chop the throttle and shut off at speed but I don't do that anyway.
Thanks Don.