4.2L aux charger output

[bc545571443]

Does anyone know the aux charger lead output on a f300 4.2?

[99yam40]

I would think it should be the same as the other battery charging circuit

[boscoe99]

Good question. I should know. But don't. From what I can remember, it is not the same that the main battery cable will provide. Will see what I can find out.

[boscoe99]

From reading on an Etec forum, the isolator lead for that model is one half of what is available from the battery cable. 25 Amps versus 50 amps.

So, if someone needed more than 25 amps for their house battery needs, it would be better to use a Yandina Combiner than the isolator lead.

[99yam40]

I was thinking voltage not amperage, my mistake

[boscoe99]

Not a direct answer but the total output of an F300XCA model is stated to be 70 amps. But of this amount, some current is used to run the motor itself. 15 amps. Leaving about 55 amps available to be provided via the battery cable and/or the isolator lead.

The battery cable takes priority in the event there is a current short fall. Let's say the starting battery is fully charged. In which case it will draw maybe an amp or so. Leaving ~54 amps or so to be available from the isolator lead. Now should the starting battery need more current, then whatever current it needs will be subtracted from the amount that is available from the isolator lead.

[bc545571443]

My aux cable seems to be about a 6-8ga and had an in-line 30amp fuse that was blown. I was wondering what size to replace it with. The blue sea chart says no more than 40/50amp for 6/8ga respectively.

[99yam40]

I would be looking at service manual or owners manual for fuse size, and try not to run the battery down too far.
also put a charger on it when even possible to keep the motor from having to put out too much to charge a dead or low battery

[fairdeal]

My aux cable seems to be about a 6-8ga and had an in-line 30amp fuse that was blown. I was wondering what size to replace it with. The blue sea chart says no more than 40/50amp for 6/8ga respectively.

Blue Sea has much good info on their site,
but I don't know exactly what you are referring to;

marine wire 'standards' come from the ABYC -
American Boat and Yacht Council
here is the ABYC wire "ampacity' chart:




Yamaha offers two Aux leads specifically for the 4.2L model,
which fits that unique engine plug;

one comes with a supplied circuit breaker,
(note the amperage of the CB)

or you can buy the same wire, "by itself":





The wire needs to be "fused" at both ends -
since it can be "powered" by both the alternator and the battery;

Your Owners Manual shows the fuse that Yamaha installs
to protect the Aux lead ("Isolator") at the engine end: