Gasket Replacements

Sea Strainer Gasket, Impeller Gasket
7/8/2009

With Mark's help, we spent some time diagnosing the overheat during our trip from Mattawoman Creek to Colonial Beach. Neat trick: stuck a garden hose in the engine water intake, wrapped it with duct tape to seal it up, and turned it on. Water immediately blasted out of the sea strainer lid! As I feared, the gasket under the lid was shot. The consequence is that, as the water demand increased when I throttled up, the impeller began sucking in air through the bad gasket instead of sucking sea water.

We made a quick trip to Napa (in Mark's rented golf-cart!) where I bought a pack of gasket material, including various types and thicknesses. I had read somewhere (the Trawlers and Trawlering mailing list, I think) that cork was a good material for sea strainer lids, so I cut a new gasket out of the thinnest cork in the pack. In addition, I replaced the water pump gasket. I had opened the pump to inspect the impeller, and the old gasket looked like it was in pretty rough shape. I had several spare paper gaskets, but it turned out that the bolt pattern was different. I punch holes in the right spots using a paper punch, and put it in place.

After installing the new gaskets, the hose test looked good. We cleaned up, and ran out for a test underway, which showed a steady 170° for 30 minutes at a high cruise speed. Simple gasket failure -- should have had a spare on board! Actually, should have replaced it long ago. Oh well, lesson learned, but at least we're good to go for tomorrow morning.