Friday, July 24, 2009

Gasket Replacements

Sea Strainer Gasket, Impeller Gasket

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.