I also have the same problem. My boat is a 2000 Larson 186 sei. It has the 3.0 ho volvo penta engine. I bought it last fall with engine problems. I fixed them but cannot get the boat to shut off with the key or lanyard switch. I did replace the ignition and hooked the wires up the same as the origina . There are 4 wires and none of them are a ground. There is a purple wire that is hooked up to the ignition terminal. When I use a 12 volt tester on the switch the positive is bright and the purple wire is dead. When I turn the key to ignition the power wire goes dim and the purple wire is dim. If I unhook the purple wire in the ignition position the power is normal again. I also have a problem with the tachometer. It goes to zero when I turn the key on but when it starts it is reading max rpm. Any help would be appreciated.
