I beleive my spedometer is a GPS type. There is a hot wire and then a wire that runs to a small red box mounted under the bow. There is nothing running to a pitot tube or anything going to the engine. The question is this, how accurate is it? It stopped workign a couple of times while underway and I am wondering if something might be loose. I dont really have much knowledge about this stuff so any and all help, advice, or anything would be great.