I want to add-a-battery

[54Hornet]

Thank You rodbolt.
So do you think I should simply get a Battery Selector Switch?
Run on one battery one day then switch and run onthe other battery the next day.
Battery 1 is the battery that came with the boat.

I want to add a battery. I happen to have 3 deep cycle batteries one year old
they are about 565 cranking amps each.

Or I could just run my livewells off the deep cycle and charge it when I get home,,,

[rodbolt17]

on that engine, thats what I would do.
the max output is at WOT and its not much.
you would have to spend several hours running at or near WOT to recharge a battery.

[RetiredGuy]

"we can stop some of the BS now.
NO AGM, NO maint free, NO dry cell.
your yamaha contact is whack whack and WRONG.

going back to your system output, you will find its not strong enough to trigger a VSR at normal speeds."

Since I have only played with 5 or 6 Yamaha's all later than 2006 and all 4 stroke machines 60's 90's 115's. Guess I will defer to rodbolt on the earlier 2 stoke units. However will stick with my earlier comments (a proper BtoB charger will enable proper AGM charging and can be used with all the engines I have looked at).

Additionally a typical "VCR" might draw 200ma and trigger at 13.3 volts so will operate just fine. I don't see it as a matter of recharging a dead or low SOC battery but instead keeping a properly charged battery topped up while on the water for days at a time. The low charging current available from the Yamaha's will easily handle this kind of operation. I use my RV solar PV system (550 watts) to properly multistage "Charge" dead batteries then the Yamaha to keep them topped up while on the water for hours or even days at a time. Works for me -to each their own

Certified Electronic technician for over 40 years, BSEE degree, Post grad training and taught broadcast engineers for 15 years. I do indeed know how to fix things as well as properly design (even redsign some manufacturers poor designs not to mention any names) them.