We bought our boat last summer, a used Maxxum with a 4.3 Mercruiser Gen II drive. The boat runs great but I noticed after a few trips that the volt meter was dropping down to around 10 volts. I checked the battery when I got home and it was 13.5 - 13.8 volts. I also found that by running the blower for a few minutes would send the volt meter back to the correct voltage. Sometimes it makes the other instruments ie trim guage, fuel guage change or "jump". Are the blower connections dirty or do I have some problem with wiring to the instrument panel?