I recently purchased a 353 fastech with 525 efi's. Both batteries are consistently dead 1- 2 days after running boat. Replaced house battery, dead after 1 day. I turn all battery switches and all breakers off after using. The only things wired directly to the battery are the amp (which is off when the stereo breaker is off), and the battery charger. The manual says mercathode system and bilge pump are hard wired to battery as well. Boat is stored on lift out of water. What is running battery dead?

G, did you try getting a meter to see if there is a draw on the batteries?? You should be able to narrow it down by disconnecting each hard wired equipment. Mike or Brian probably has one and should know how to check for current flow.

May be a dead short somewhere... I had that with a car I had once and did the same thing. Mine had 2 wires melted and created short.