No helm power - 2018 Yamaha 704 w/ 2021 F150LB 4 stroke

[vette454]

Folks,

I'm on day 3 living under the dash of my pontoon. Boat ran fine on Friday, come saturday morning the engine controls for were dead. No ignition, volt guage, tach, fuel gauge, trim all dead. I've verified power up to the helm (12v) and ground in the 10 pin back to battery. I wrung out the ignition switch and even slaved in a new one with no change. I verified the neutral safety switch was working but that shouldn't affect the gauges. All gauges are analog. All lights, live well pump, radio horn work perfectly. The only fuse I can find under the helm is for the radio. If anyone knows where there may be a hidden fuse in this harness, or other troubleshooting ideas, I would be eternally grateful.

 

[99yam40]

does the red wire to the key switch have 12 +?
when turning the key to the on position it should put 12+ on the yellow wire.

Should be some fuses on the motor

 

[vette454]

I have +12.5v at the 10 pin connector (motor side) for the remote harness. But when I measure voltage at the other end (8 pin between black and red), I have +9.5v. Built a jumper to go from an engine ground lug then remeasured to the red wire in the in the 8 pin connector, still 9.5). Shouldn't have that much voltage drop over 15'. All fuses ohm good... Though all the diagrams show a "dual fuse" harness going to the gauges and I can't find one anywhere. Still, 9.5v should stimulate some of the analog gauges, shouldn't it? Gonna go on a hunt for shorts in the harness...

 

[saltchuckmatt]

I have +12.5v at the 10 pin connector (motor side) for the remote harness. But when I measure voltage at the other end (8 pin between black and red), I have +9.5v. Built a jumper to go from an engine ground lug then remeasured to the red wire in the in the 8 pin connector, still 9.5). Shouldn't have that much voltage drop over 15'. All fuses ohm good... Though all the diagrams show a "dual fuse" harness going to the gauges and I can't find one anywhere. Still, 9.5v should stimulate some of the analog gauges, shouldn't it? Gonna go on a hunt for shorts in the harness...

This may sound stupid but do you have super clean battery connections? I recently had problems at my trim and tilt. When I tested power at the engine I had 12.7 volts so I figured must be t&t relay or worse. Messed around for two days before I tried to start it. No start. Put my meter back on the lug while I had my son try to start it and 5 volts. Cleaned the batteries and everything worked. By the way, before cleaning them I would have sworn they were clean. Also, do not use wing nuts!

 

[vette454]

Thanks for the tip... I started there... I actually have a manual circuit breaker that interrupts power to the dash and motor running voltage. And its rusted to the point that I can't get the lugs off. Still, I get 12.5 at the starter solenoid, and engine to helm disconnect. I think I've trouble shot it down to a damaged harness when I had the boat repowered last hear... After tugging and twisting on wires for the last two days, I've shot every wire in the harness and find the red power line now OPEN... Leading me to the next logical conclusion, broken splice or crushed harness... I'm about to spring for a new harness just to slave it in and prove myself right...

 

[saltchuckmatt]

Thanks for the tip... I started there... I actually have a manual circuit breaker that interrupts power to the dash and motor running voltage. And its rusted to the point that I can't get the lugs off. Still, I get 12.5 at the starter solenoid, and engine to helm disconnect. I think I've trouble shot it down to a damaged harness when I had the boat repowered last hear... After tugging and twisting on wires for the last two days, I've shot every wire in the harness and find the red power line now OPEN... Leading me to the next logical conclusion, broken splice or crushed harness... I'm about to spring for a new harness just to slave it in and prove myself right...

Yes, I have the auto circuit breaker going to the dash or main positive bus bar. Every three years or so I have to cut them out because they get all corroded up.

My harness failed twice. Right where it goes into the motor because of the steering action going back and forth. 1st time while trying to find out why I didn't have power to the motor, I turned the motor trying to get better access and luckily I had the key on and I heard the pumps all turn on in the motor. I jiggled the harness and it would come and go. I butt spliced that one (starting of boating season)but then the next year another wire went at the same spot. I was going to buy a new harness but after looking at my old one it had plenty of excess wire in the bilge area. So I pulled more in the motor, cut all of them and then solder spliced them back together. I figure every 5 years or so I better do them again!