Jeff: Sorry for the delay in responding, but I just got home from the second leg of our trip (from Mobile, AL to Peoria, IL.). Modem connections were not easy to come by on the Mississippi! The exhaust outlet is above the waterline, although just by a couple of inches. According to the Onan factory rep who visited the installation, the water got in by siphoning past the raw water impeller. He said that contrary to popular belief, those pumps are not water tight, and given enough time, enough water can get past to cause a problem. The fix was two things: First, we installed a siphon break in the raw water line between the heat exchanger and the exhaust water injection elbow. Secondly, we installed a dry exhaust adapter, which is a vertical fitting about six inches high above the exhaust manifold. To that, we installed a short pipe nipple, then a 90 degree elbow that turns the exhaust horizontal, then a 45 degree elbow installed aiming down with a hole drilled into it and a 3/4" pipe elbow brazed into that to provide the water injection point. >From there a conventional hose leads down to the wet muffler. This whole contraption was wrapped in asbestos tape and then saturated with a high temperature epoxy. The purpose of the second part is to get the top of the fitting above the waterline to prevent water from backflowing from the exhaust if it should ever fill up again (presumably via the through hull, since the siphon break will prevent it from coming in via the raw water intake). It would also prevent excessive cranking (which can fill up the muffler) from causing water to backflow into the engine. All together, a very slick installation, and well done (by the folks at Middleton Marine at Dog River Marina in Mobile, AL. The only problem was it cost too much and took too long... Imagine that ;-). Best regards, Mike Fairbairn ----- Original Message ----- From: jeff nicholas <jeffnick@bellsouth.net> To: Trawler World List <trawler-world-list@samurai.com>; Mike Fairbairn <mike@rmcars.com> Sent: August 13, 1999 7:16 PM Subject: Re: Expensive Generator Lessons > I've been thinking about this since you posted. I'm curious how the water > got into the cylinders. I'm assuming it was raw water. If it was raw > water, it either came in via the exhaust exit, or it came in from the pump > side of the cooling system. If the exhaust exits the boat above the > waterline, the only way raw water could get into the cylinders is past the > impeller. I guess it's possible, but I wouldn't expect a properly working > impeller type pump to allow a syphon. > Is the raw water pump an impeller type? > Did the impeller self destruct? > Was the exhasut exit under water due to being moored against a current, or > was the boat low on her lines or secured too tightly against a rising tide? > Or maybe it was freshwater in the cylinders??? This would certainly be an > installation/maintenance issue. > > Nick in Spartanburg, SC > > >It turns out that water had gotten into the engine, and it had hydraulic > >locked, bending two rods and breaking a piston.