Grainger sells a surface-mount thermal snap switch for about $15. which can be ordered to close at a specific temperature. I have one hose-clamped to the exhaust on my sailboat's Perkins. I think it's a 130-degree. It closes within a minute of cessation of water flow. Heard about it years ago from Norm on the liveaboard list. John (aboard "Truelove" in St. Anne, Martinique, FWI) "Seahorse" Jim McCrea writes: > Milt gave an excellent description of his reasons for a wet exhaust rather > than the more Nordhavn conventional dry exhaust. I am wondering if Bluewater > will have any alarms on the wet exhaust on the main such as either a water > flow sensor to high temperature alarm or both or none. On my boat I added a > Wet Exhaust Temperature Alarm from Borel Manufacturing (_www.borelmfg.com_ > (http://www.borelmfg.com) ) and am considering adding that and a Raw Water Cooling > Flow Detector on the new boat. My thought is that I would rather know of a > problem before the overheat alarm on the engine goes off as I am sure that I > don't watch the temperature gauge often enough to be sure that I would catch > the problem in its incipient stage on temperature gauge.