Good morning. Maybe someone can help me with a perplexing problem before I
have to turn it over to an auto/boat electrician. The boat is a Buccaneer
470 with an 82 Evinrude 90hp V4. I use it trolling for Trout on Lake
Toupo - running the main engine about 30 minutes a day, and on the trolling
motor (no charging coil) for about five hours a day. The ignition is always
switched off when trolling, and the fish-finder draws 350mA. The battery is
new (2nd one I have purchased) and has 44 amp hour reserve capacity)
The symptom was a flat battery after three days connected to the main
terminals. I had an isolating switch installed and used it at night to
isloate the battery. No difference - flat battery again after four days.
So I put a multi-meter in series with main positive terminal and I found
that there is a 32mA current drain with everything turned off. With the
battery isolator switch on the off position, no current drain. The boat
shop checked the rectifier and charge current - reported as all OK. (?)
Then I began to disconnect all the electric service wires at the battery one
by one - fish finder, nav lights and ignition. No effect on current drain.
It was the main wire to the engine (presumably the ignition/charge wire)
that was drawing the current. Fishing around in the engine (I am no expert)
I could not find any spurious voltage. The main (large diameter) red to the
starter solenoid was live, as was one smaller red wire to a centre relay
connection - but that was it. I then checked all the metal fittings, engine
casing, boarding ladder, etc, in case there was a short somewhere - no
result.

So, sorry about the long-winded preamble, but what should I check next??

Thanks

Bob McMillan
New Zealand