charging question on twin 115 4 strokes

[afn63537]

Hello Everyone,
We are running a set of Yamaha 115 4strokes on a 2000 model 22 foot Prokat with Yamaha gauges. The single indash guage is currently getting a blinking voltage of about 11.8 down to 11.6 while running. We have what I thought were 2 completely independent electrical systems setup with 2 batteries in parallel on each side with no switches involved. The voltage guage powers up with the port side key switch only, so does it only reflect the condition of the port side charging circuit? We tested each side with a voltmeter with engine off at the battery terminals. Port side was 12.6V and after cranking engine didn't get above 12.5V
Starboard side was 11.8 and after cranking engine didn't get above 11.6. Don't they charge at idle?
Doesn't seem likely that both independent systems would go bad at the same time.
thanks in advance

 

[rodbolt]

Re: charging question on twin 115 4 strokes

only the voltmeter attached to the key switch will read that switches voltage.
do you have ALL battery negative posts bonded with a wire no smaller than the largest ground wire?

 

[afn63537]

Re: charging question on twin 115 4 strokes

There are 2 batts on the port side and two on the starboard side. Since they are connected in parallel on each side, there are heavy cables connecting the negative terminals of the batteries to each other as well as the positive terminals to each other , but no heavy cables run from port to starboard, just back to the respective motors.

there are ground wires coming from the negative side of each battery pair to a ground buss (or block) behind the dash where all components get their ground.
These wires are at least as heavy as any wire located on that buss and any other accessory wire going to the neg terminals on the batts.

should both motors be charging their own battery set?
should they both show over 12 volts when running at idle?

thanks for your help

 

[rodbolt]

Re: charging question on twin 115 4 strokes

USCG requirements are that al negative terminals on all batteries mut be bonded,hooked together, by a cable not smaller than the largest ground wire.
its that simple and for a reason.\

 

[afn63537]

Re: charging question on twin 115 4 strokes

the motor cables are 4 gauge copper and only 6 months old.
I've added a similar wire going from the left battery bank neg terminal to the right battery bank neg terminal.

 

[rodbolt]

Re: charging question on twin 115 4 strokes

each engine should idle at about 14V.
if not start testing stator output and regulator output.
each engine also has a battery isolator built in the regulator to allow charging a house or second battery.

 

[afn63537]

Re: charging question on twin 115 4 strokes

i've looked on the forum for more info on testing and found the following:

"look for a large round plug with 3 green wires" to do the stator test, but can't find anything like that on these F115s

i took off the front plastic cover over the electronics and fuses
it looks like a regulator/rectifier is mounted there
is that where i should start?

 

[rodbolt]

Re: charging question on twin 115 4 strokes

start by purchasing a factory yamaha shop service manual. it will come in handy.
best I recall the F115 and F150 use a flat 3 wire connector for stator to regulater and a flat 3 wire out.

 

[afn63537]

Re: charging question on twin 115 4 strokes

I'm looking for the manual now.

the rectifier/regulator has a 5 wire connector coming out of it, 3 of the wires are the same color white, then there's a red one and a black one

isn't it strange that both engines would quit charging at the same time?

 

[rodbolt]

Re: charging question on twin 115 4 strokes

the 3 whites are stator lighting coil inputs, its an AC voltage.
the red is regulated DC voltage out and the black is the ground.
its not uncommon if the battery grounding was not done to USCG specs.