2005 Mercruiser 5.0 Motor wont stay on

First time boat owner....just took boat out of wet slip to clean the hull....and as I was cleaning it in my driveway, the battery died on me. I checked out the battery and it was bad. So once I replaced the battery with a brand new one and tried to start the boat it turns over, but once i let the key go, it immediately dies. I dont know much about boats but I am a alittle bit of a car guy. I don't know how close these motors are to car motors, but I really could use some help.

I am also wondering where i might be able to get a manual for this motor?Is there one for boat motors like there are for cars? PLease help!!!!!!!!!! I hate to have to take it in to a shop if its something that I can fix!! Any ideas???

Re: 2005 Mercruiser 5.0 Motor wont stay on

Something tells me you have bad battery connections and/or cables. Clean up the battery side terminals, cable ends, etc, and toss wingnuts if you have them for stainless steel nylock nuts.

Re: 2005 Mercruiser 5.0 Motor wont stay on

Jason...I have been cleaning the boat all over thoroughly on the driveway while playing the radio during it, and thats when it had slowly dies on me. So I then took the battery out to get checked and thats when they told me it was dead. So I replaced it and once I put the new wing nuts back on, the boat was able to turn over while the key is turned on, but once I let go of the key it turns off.

Could it be just the cables/connections? I put the wing nuts back on but I am pretty sure they were connected pretty tight. What about the starter/starter solenoid? Could that be a problem? I will go ahead and change to the nylock nuts but can't imagine that being the case. Any other ideas anyone??