I've recently developed a problem with burning the ignition switch fuse when I try to crank the engine over.Engine/Ignition info: 1987 Volvo Penta AQ-260 (GM 350) with a three position key switch (Off,Run,Start). The engine was rebuilt last year. The starter and the switch are only a year old.The odd thing is that it doesn't do it every time I start the engine. But sometimes I go through a whole box of fuses before I can get it going. My initial thoughts are faulty ignition switch or a dead spot in the starter that is causing it to draw high amperage.I need your help with ideas that could cause the fuse to pop, and help with testing the switch and starter. I have a multimeter but am far from proficient at using it.