Roger Long wrote:
Calder points out how battery life is increased by minimizing
discharge level. No matter how many batteries you have in the boat,
you'll get maximum life by putting them in one bank. Keeping a
starting battery isolated and in reserve is obviously a necessary
compromise for most craft. However, with a 20 hp diesel, modest
starting loads, and the ability to hand start, I'm thinking that the
simplicity of a one bank system might make sense for a daysailing,
short cruise boat, that is docked with shore power. If the batteries
did get run down away from home, I'd be willing to hand start in
penance.

The key question is whether a two cylinder diesel like a 20 hp Yanmar
2QM can really be hand started or if it is an "only when your life
absolutely depends on it" kind of operation. I don't have much
experience with engines under 200 HP so I'd appreciate the benefit of
actual experience.

Only if your life depends on it is about right. I've seen somebody
hand start a 1 cylinder YSM Yanmar and it wasn't pretty. Those ones
have a huge flywheel.

How about using one of those little portable "booster batteries" that
basically provide a jump start to a mostly discharged battery? They
are only about 15 lbs and pretty compact.

They might not start a 2QM without another house battery providing
some current but I bet they would start it with a depleted house bank.

Evan Gatehouse