Yanmar Pleasure Boat Marine Engine Help

ELECTRICS

CAUTION: Do not connect the battery to the wrong terminals, the diodes in the alternator will blow and are expensive to repair, THIS IS NOT WARRANTY!
If the alternator light doesn't go out after the engine is started, this is the cause 99.99% of the time.
The positive ( + ) battery terminal must be connected to the battery switch, thence the starter motor solenoid. The negative ( - ) terminal is connected to the bolt that holds the starter motor.

If you dont know anything about electrics, hire a pleasure boat marine electrician or auto-electrician.
Use automotive type wiring for marine use ( multistranded, tinned ) to prevent later disasters.
We found the best cable to use for starting is 100amp welding cable. It is mega-multi-stranded and has a decent cross-sectional area that can handle heavy current flows with minimal voltage drop.

I once did a seatrial on a new sailboat that had a wind generator, solar panels, a little industrial Yanmar generator and an additional engine driven alternator to the optional 80amp one. Apparently the owner had been caught short offshore in his previous boat and wasnt going to suffer again. Three months later the switchboard caught fire, not only leaving him without power once more but creating a more serious problem as acrid smoke and flames came out from the Nav Station. I'm still a fan of the 'KISS' principle.

Too small a cable can cause problems like the one above but again, I was on a job in Japan where the electrician turned up with ship cable to wire the 50 footer. No amount of arguing by the boatbuilder would change his mind. Even twin 750hp MTU's couldnt make the boat go as advertised with nearly 3/4 of a tonne of cable....

Batteries

The battery should be within arms reach of the starter motor , any further and the voltage drop can give problems, not on a normal day, but when you're dragging the anchor on a lee shore in the middle of the night after a long party where the stereo, and all the other toys, were getting a good workout.
Every installation should have a starting bank and a house bank. Each bank may only need one battery, on a larger vessel there may be several batteries in each bank, it depends on how much electricity is needed. Each bank has a switch that can isolate it from all loads. When stopped for the night always switch off the starting bank. When leaving the boat unattended, turn off everything! A separate circuit to the house battery for the anchor light is a good idea.

How big should the starting battery be? Yanmar give amp/hours as their criteria but the way this is calculated is different between battery manufacturers. I prefer to use CCA ( cold cranking amps ) to define the battery size.
GM series: 200 CCA
JH series ( except 3JH3E and 4JH3E ) : 250 CCA
3JH3E and 4JH3E: 300 CCA
4LH series: 500 CCA
6LP series: 600 CCA
6LY series: 800 CCA
6CX series: 1000 CCA

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