When using silent choice it is often said that you should not run the exhaust through the drive when the RPM goes above 2000-3000 rpm because it can hurt the engine. Does anyone know what the problem really is? In what way does it damage the engine? Will the pistons melt?

I have a 502 MPI with a Bravo One drive that I run with silent choice and a tube style open ended exhaust hose down at the drive. It seems to run quite OK also at WOT with the exhaust through the drive.

I think the problems are with more the high performance engines. When you run high cam overlap you have a tendancy to get reversion. Where the exhaust can actually suck back into the cylinders. And with cooling water getting mixing into the pipes you dont want water getting into the cylinders cause engines dont like to compress water!!! For the most part on stock engines silent choice dont hurt....obviously Merc and other OEM's have done their homework on the production engines or they wouldnt be running boats with thru-prop exhausts if it hurt.