Mercruiser electrical problem

[Kirk Braito]

I've got a 4.3l 2004 sterndrive and the battery was conked so my buddy switched it and (grrr) put positive to negative and visa versa. Now the dash panel is dead and there is no power except to the power trim. The breaker switch is not tripped (unless it is REALLY hard to push) and there are no blown fuses in the dash fuse panel. Help! I wanna go fishing and don't have the $ to take it to the shop to find what is probably an easy fix???

 

[Bt Doctur]

there should be a small square plastic looking box mounted to the starter main connection. its a 90A fused safety device. This is the first point the boat systems get there power.power flows thru that wire to the engine breaker (yes ,it is that hard pushing), thru the engine harness plug and up to the dash.You can verify this by using a jumper from the battery to the red wire at the plastic block.Plan on possably replacing the alt too. they usually blow the diodes with reverse battery.