Here's a repost from Kohler gensets
This is what Kohler says:
"In theory it sounds like a good idea, but in reality it has a catastrophic result. Let me explain, when the generator
is not running and the vessel is underway, the pressure that is induced to the sea water pump varies; however, a sea trial has shown with as little as 14 inch water column or .5psi the sea water pump impellor will deflect. When this happens the sea water will trickle/flow (depending on pressure) through the heat exchanger
, exhaust mixer, and ultimately stop at the engine silencer. At that point, water backs up through the engine exhaust resulting in flooding the engine and vessel. In order for the water to discharged out of the muffler
, the engine must be running. In other words, it must be running. Exhaust pressure is what forces the water through the super silencer III.
Acceptable sea water through hulls are illustrated in Figure 3. Speed scoops and sea chests are not