With the move to underwater exhausts, we have no visual indication of water flow in the exhaust system. We do have an electronic flow alarm on each engine, and temperature alarms on each injection elbow, but not seeing the water flow has made us uncomfortable. Thanks to Mark Fritzer we now have an answer.
The impeller in the bronze housing above gives us a good visual indication of water flowing. This is not cheap, costing close to $400 retail for each one. And at first we balked at the cost. But now that we have seen these in action, we’d fit them again even with an above-the-water exhaust system.
There are a couple of negatives. First, the pin on which the impeller rides is stainless steel. It will eventually go away, 316 not being particularly happy in salt over a long period of time. Next, the cover plate is mild steel and is going to rust. We’ll have to protect it in some fashion. The cover plate comes off and the glass can be removed, and the pin replaced.
We have mounted these in the salt water line just before the injection elbow of the exhaust system, well above the water line, where it should remain dry most of its life. That should help the wet stainless parts survive. Alternately, if immersed, this could be bonded to the engine and its zinc system to give the parts protection.
We shall report in a few months as to how these are holding up.