Testing alternate battery starts

[JHeide]

Silly ruminations mid winter here in NY while boat is high and dry…

Next season, I’d like to test the process by which I can start an engine using the other engine’s battery. I know I can start an engine using the switch and have done so. But how do I know it’s really using the alternate engine battery? So what I want to try is switching the starting engine’s master battery selector switch to off, and then start that engine using the alternate start option which will theoretically use the other engines battery to power the start. Makes sense?

Is there any problems with doing this I haven’t thought of? I likely will start the engine, let it warm briefly, and kill it, then reset its master battery selector to on before continuing. Is there a problem with an engine running and its battery selector switch off?

 

[Bmarler]

Silly ruminations mid winter here in NY while boat is high and dry…

Next season, I’d like to test the process by which I can start an engine using the other engine’s battery. I know I can start an engine using the switch and have done so. But how do I know it’s really using the alternate engine battery? So what I want to try is switching the starting engine’s master battery selector switch to off, and then start that engine using the alternate start option which will theoretically use the other engines battery to power the start. Makes sense?

Is there any problems with doing this I haven’t thought of? I likely will start the engine, let it warm briefly, and kill it, then reset its master battery selector to on before continuing. Is there a problem with an engine running and its battery selector switch off?

Only if the alternator has no destination.

 

[Bmarler]

It would verify without leaving the helm if you have volt meters on the batteries you could monitor.
Just make sure the proper battery is showing voltage drop when cranking.

 

[gilbertpark]

See my post a few minutes on exactly this topic

 

[SteveK]

remove the battery cables from the battery you do not want to use. Then with volt meter check for power at the ALT red and engine ground. You should not see anything until you turn that switch to send power to that engine. Once confirmed go ahead and start.