Saltwater Corrosion – Under the Cowling

Saltwater Corrosion – Under the Cowling
The past few months have brought us several cases of severe saltwater corrosion damage that occurred under outboard engine cowlings. These photos are from Yamaha and Evinrude outboards but the issues I am describing here can and will affect all brands the same.

Saltwater can get under the engine cowling in three ways: 1) Through the cowling and/or pan seals. 2) Via a leak in the engine's cooling system. 3) Through the air intake system at the rear of the cowling.

Saltwater entering past the cowling or pan seals usually occurs when the cowling is not installed and/or latched correctly. Removing the gasket from the lower pan and cleaning occasionally is a great practice. Applying Corrosion X Red will help keep this gasket in pliable condition, allowing for a good seal.

Catamaran hulls or boats where the engine is mounted very low on the transom can have seawater wash over the top of the engine when the boat comes off plane abruptly and also when running in a heavy following sea.

A saltwater "trailer" will be visible no matter how or where the leak originates. This will be a sign to change your operating techniques and also to inspect more regularly. Spraying the powerhead with Corrosion X Red is a great preventive measure.

The other areas to inspect will be more subtle and will require a little more looking. The water pressure line, cooling system pop-off valve, or head gasket can produce enough salt spray to be ingested into the engine that after sitting for two weeks or so, the engine could be locked up due to corrosion occurring inside the engine. If the engine does not lock up, the ingested salt will definitely shorten the life of the engine.

Pull the cowling regularly and investigate any visible sign of saltwater entering under the cowling. No matter how well they are built, saltwater can destroy anything!

Good fishing and safe boating,

Chris Mapp

Coastal Bend Marine
Port O'Connor, TX
361 983 4841