Define 'significantly'. If you're starting only once in a while, as
most sailboats do, I doubt that you'll notice the shortened life.
Are you buying new batts, or are there 2 DC already in your boat?

I had the separate start batt and a DC, When the DC went , I replaced
with a DP (that's all the local Sears stocks anymore). When the
starter batt goes away, I'll go with a second DP. I have a manual
separator switch.


--
Scott Vernon
Plowville Pa _/)__/)_/)_


"Roger Long" wrote in message
...
I understand that but, is the load on a 20 hp diesel that you can
start by hand high enough to significantly reduce the life of the
battery?

--

Roger Long



"Scott Vernon" wrote in message
...
Yes, a deep cycle will start your Yanmar, but you are reducing the
life of the battery by doing so.

There's a reason, other than marketing, why batteries are labeled
'starting' or 'deep cycle' or 'dual purpose'.
I believe the main difference is the thickness of the plates.
Starter
batts, are built for short duration, high loads. DC are for less
load over a longer time period. DP are a compromise between the
two.


--
Scott Vernon
Plowville Pa _/)__/)_/)_


"Roger Long" wrote in message
...
Is there any reason to consider using dual purpose or a one
starting,
one deep cycle set up with a 20 hp Yanmar diesel? I would think
the
starting loads on the small engine are low enough that two deep
cycle
batteries would do fine.

--

Roger Long