How Does Water Enter Outboard Engine Cowlings?

Boats with twin engines, specifically most catamaran hulls, are susceptible to water entering the engine powerhead through the fresh air intake located at the top-rear of the cowling. Some engines have intakes on the sides of the cowling to reduce this tendency.

Water intrusion is not always the result of direct flows of water into the intake. Chopping the throttle suddenly when underway causes the boat to decelerate quickly, allowing backwash to overtake the engines.

Another possibility for direct intrusion is sloppy seas slapping the back of the engines while the boat is at rest. This is exacerbated when the engines are allowed to idle the entire time offshore. The engines take in fresh air, and the localized low-pressure area invites spray and mist to enter the intake.

The last scenario is less defined because there is no direct intrusion involved. The situation develops due to mist created by the vortex between the engines while underway. The photos reveal how unavoidable saltwater mist over extend periods can degrade engine components.

Regular inspection by removing the top belt and flywheel cover is recommended. Liberal applications of Corrosion X Red is the best prevention toward circumventing costly repairs.

Have a great winter fishing and boating season!

Chris Mapp

Coastal Bend Marine
Port O’Connor, TX
361-983-4841
[email protected]