Boat starts but then dies..Battery Question

[Kevinsheehy]

So 2 days ago I went to start my 19' bayliner capri with a volvo penta engine and it would not start. Battery was dead. In hopes to make it to the lake to meet friends I put the battery from my car into the boat in hopes that would give me a temporary fix then I could get a charger and charge my boat battery. Upon swapping the battery the boat would start up (Although not easily and not everytime) and then when it did start it would die once I applied throttle or shortly after starting even if I didn't throttle it. Is anyone familiar with an issue like this with having a battery that is too small in the boat and trying to run it on it or do I have another issue that isn't part of the battery. Any ideas. I plan on charging my boat battery tonight and finding out for myself but since I am at work and I have this on my mind any insite would be a appreciated.

 

[Steve Mahler]

Re: Boat starts but then dies..Battery Question

You must have 2 separate problems. The battery would not cause the engine to die, or idle poorly. Those issues suggest a likley fuel problem. Has it been long since the engine was used? Carb could be monkeyed up, or really bad gas - water in gas can have that same stalling/lack of idle effect as well.

 

[Silvertip]

Re: Boat starts but then dies..Battery Question

Battery that is too small, or not fully charged, only affects the ability of the battery to spin the starter to get the engine running. Once running, the engine draws far less current so a motorcycle battery would likely keep it running. If your boat has a voltmeter, what does it read with the key in RUN -- but engine not running. Repeat the check with the engine running at about 1500 rpm. Battery static voltage (charged but engine not running) should show about 12.6 volts. With the engine running the system should show 13.6 to about 14.5 give or take a couple tenths.

 

[H20Rat]

Re: Boat starts but then dies..Battery Question

Battery that is too small, or not fully charged, only affects the ability of the battery to spin the starter to get the engine running. Once running, the engine draws far less current so a motorcycle battery would likely keep it running.

better yet... once running, you can yank the battery completely out and your carbed engine won't even care!! (depending on the type of alternator, you MAY fry your diodes. And most ECU/EFI engines, yeah, don't try that...)

A running engine doesn't draw ANY current. (if it did you would have to charge the battery from the wall outlet occassionally....) The only reason a battery exists after startup is to control voltage put out by the alternator and buffer the noisy electrical signal. Nothing to do with the engine itself.


Anyway, all that said, like the poster above mentioned, you have two different issues. If the engine spins over fast enough, your battery is fine.