For those of you with twin engines and the factory alarm system, you might want to consider this. Of the many things I've done on mine, separating the alarm system--so it alarms either engine separately (instead of both together)-was both worthwhile not hard to do. Furthermore, it makes a great winter project for most of the fabrication can be done at home.
To wit: The alarm system on twin-engined Marinettes works by switches that ground out to set off the alarm: the oil pressure switch and excessive temperature switches--one in the engine and one in a riser. Unfortunately, to save a few bucks, they used only one alarm system for both engines. Therefore, when firing up, say, the port engine, the alarm goes off since there is zero oil pressure on the starboard engine. Dumb, and right when you need the alarm most. Worst of all, if you like to save gas by running on one engine, you have to turn off the buzzer--not a good idea!
There's two ways to eliminate this nuance; the easy way (mine) and the complex way. My way is also cheaper--I know, you're shocked!
The expensive way is to somehow find and isolate the wiring for the alarm system on one engine--take your pick--then rewire the other and add another noisy buzzer.
My way is to isolated the oil pressure signals on each engine by the use of a relay. I bought my three (one spare) off eBay for a few bucks, then wired them up as shown in the sketch. The relay keeps the oil pressure signal open until THAT engine is fired up, so you can start the other one with the alarm turned on.
Jeff
fastjeff attached the following image(s):
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell
