Well, you might be right about the common cable and the cheaper
route/solution being the flooded battery, but I can find a 30 amp
isolator for $140. But if you must have that overpriced Guest stuff,
yeah, you'll pay $300 for it.

BTW, agm's are not quickly ruined by having over 14 volts on them. We
use hundreds of Lifeline agm's where I work and the bulk charge spec.
for them is 14.2-14.4 volts. Float charge should be kept at 13.3 or
under. And once fully charged, can be equalized at 15.5 volts for 8
hours when neccessary. As stated in their documentation: "Regardless
of what some rumors portray, AGM batteries are not as sensitive as
once believed. They often get confused with Gel Batteries, which are
very sensitive to voltage and they need a special charger."

Eric

On Nov 14, 9:06 am, wrote:

Yeah, and a 30 amp galvanic isolator to protect that $150 AGM battery
will run you about $300 or more! If the Honda outboard in question has
electric start, you will need one that will handle 100 amps, as that
is about what the starter motor draws, and the same cables from the
motor to the battery are used for both starting and charging.

I'll repeat: A new flooded battery will solve the issue for about $50.