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Stainless Water Lift Muffler Corrosion

Category: Engine

Contributed by Chris Woodbury

Summary: A weak point on our boats that needs watching for corrosion and leaks.
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As Mac Caldwell pointed out, a weak point on our boats is the stainless water lift muffler. Sea water flows through this and stands in the bottom of it when the engine is off, resulting in the opportunity for corrosion. Eventually the weld leaks, due to stress corrosion from the heat of welding and the chlorine in the water. If this progresses you will see rust stains under the muffler and eventually salt water under the engine.

We have had our muffler rewelded twice, with some success, but Mac suggests that the only permanent solution is to have a fiberglass replica made. This approach worked well for him on SEELOWE.

Perhaps an easier way to do this would be to purchase such a muffler from a marine supplier and have the ports remolded in the correct configuration.

muffler diagram

In any case if you have one of these mufflers, check it frequently by feeling its bottom. If you find it is wet and dripping, plan a repair in the next few months. If the leak sprays water around the compartment, get it fixed soon because this corrosive water will do damage. Find a good welder, as this is a difficult repair, due to the contamination of the stainless in the leak area.

I know we discussed mufflers last issue, but more has come to light and more of you have told me about problems in this area. I checked with the Mother Yard and found they are still fitting the Stainless Steel units to new boats. The are available as spares at 1,420 FK, about $280, plus shipping, and are basically the same units on all our boats with different connections.

See an enlarged diagram: ~/tips/images/mufflerdiagram_lg.gif