3-2-1 Nothing!!!

Saturday was boat day! I was home working like mad to finally get the Mastercraft back in the water. Vacuumed everything, washed everything, vinyl stickers of boat name on, water pump installed and working, seats scrubbed, new speedometer installed, dash reassembled, Windshield installed, floor painted with texture paint, batteries charged and installed with terminals cleaned, de-winterized boat by installing all plugs and were ready to put in the water! Ready to turn key to check that we have ignition 3-2-1 nothing!!!!! Just a weird click sound and then all power to the boat goes dead. Checks fuses checks battery connection all good still nothing. Hmmm... 5 minutes later the blower comes on all by itself must be a reset switch on the engine. So we try it again with the same results 5 minutes later I got power again. Time to call it a night as rain is due for the next 5 days so I'll ask around and try to figure it out let us hope its something simple I can't not have it running this year.... SIGH

Update: After a call to Mastercraft they feel it is a battery terminal connection problem. I have two batteries with a switch one of them I know is dead so... In theory if I switch over to the good battery "ONLY" it should turn over. I'll check it out and put a charge on the other dead battery. SO close to being on the water again...