I have a 1982 40hp two stroke engine. When engaging switch to turn motor over, it acts like the battery is low. It barely turns over and then will suddenly turn over normally. It seems to worsen if I have trouble with the engine firing and continue to try and start it. The process repeats itself each time I start the engine. It runs fine once started. My mechanic had replaced the switchbox with a used switchbox because I was not getting fire. Could this be the source of the problem? The battery is not low and the wires to the motor from battery have been replaced.