Rust streaks from exhaust

[glynhome]

I have a moody 41ac with a Volvo 55hp engine. Recently rust stains have appeared on the hull below the exhaust outlet and there is a rust tide mark in the outlet tube coming from the Vetus anti-syphon valve (photo).

The boat is only 18months old and I'm concerned that seawater is feeding back into the engine when the boat is heeled to starboard. I've also noticed that when the engine is running there is a lot of air coming in through the anti-syphon valve on its outlet side, is this connected to the problem or is it normal?

The anti syphon valve is mounted above the engine and the rust tide mark in the outlet tube is roughly level with the top of the engine.

I am pushing the manufacturer for an answer but any suggestions on the probable cause would be welcome.

Glyn

[glynhome]

Problem solved. The cast elbow feeding water into the mixing elbow from the anti siphon valve was fitted upside down, so seawater was sitting in the pipe and eating away at the elbow over the winter months. I've fitted it correctly and now it drains when the engine stops.



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