SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

How much battery charge to start engine

1847 Views 18 Replies 12 Participants Last post by  jrcanoe
Hi All,

I'm scheduled to launch on April 17, and when I made the drive to the boat this past weekend to test the batteries, the starting battery (Group 31 lead acid) showed 12.52 on the multimeter, which according to a chart I found online is 85% charged. The battery is only a year old, and was topped off before winter storage (indoor heated), and ALL the batteries were disconnected from everything. This is the only battery that has dropped significantly, albeit slowly, during the winter. The two 4D's are still showing more than 12.7 on the multimeter.

Is the Group 31 at 12.52 enough to start the engine (Westerbeke 30b3 diesel) in a couple weeks?

As always, thanks so much for any help! :)
1 - 2 of 19 Posts
That should be plenty. A Westerbeke 30b3 isn't a huge engine. I would think that even a 50% charge would be plenty, as long as there isn't something else wrong with the engine that makes it "hard starting". If worse come to worse you can always use that 4D bank get her started. Starting a little diesel with a deep-cycle bank won't hurt anything.
  • Like
Reactions: 1
Yes diesels are higher compression and without spark plugs it is that compression that ignites the fuel air mixture.
Actually, it's the heat from that high compression, rather than the compression itself, that ignites the fuel-air mixture. The difference may seem a somewhat trivial point, but that is why the engine has to crank fairly fast, otherwise the heat will dissipate too quickly (in addition to the compression bleeding past the rings) and ignition temps can't be achieved. Of course, some diesels also have glow plugs to help the situation.
1 - 2 of 19 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.