fuel gauge/tilt trim

[dunk68]

I tried posting this earlier and my inet connection died. So here we go again

I have a 20 ft. pontoon boat with a 1998 Mercury 4stroke with quicksilver controls. I assume this problem is in the control box or the wiring.
My tilt and trim(on the control) and gas gauge quit working the last time I was out. When I turned on the dash light and the key was turned on, the gauge worked and the tilt and trim worked. The tilt and trim button on the motor works all of the time. My tach had quit working about 2 weeks ago. It just sits on 1000.
I assumed it is getting power when the switch is on. Today I tried to crank it and no power. When I turned the dash light on, I can crank it. I'll try the ground wire from batt. to gauge terminal tomorrow. But I assume my loss of power may be in my control box? There is no plug at the box, all the wires are connected inside the box individually with bullet connectors with rubber "insulator"covers. I have no idea where to check the tilt/trim connection in the control box, or the tilt trim.

Gauge problems I was going to run new ground and hot wire, but don't know if that would help. All other switches (Horn, Navigation, Accessory) work. I recently rewired the fishfinder, stereo, and driving lights with a fuse block. There are no problems with that connection. So now I have a fuse block to connect new wires to for the other functions. Any help on where to start would be appreciated.

 

[Silvertip]

Re: fuel gauge/tilt trim

Let's separate the failures into "common" and "separate" to begin with. The fuel gauge is the only function that does not run through the harness from the engine to the control box. It is a separate wire that runs from the sender on the fuel tank to the "S" terminal on the gauge. The gauge requires 12V and ground to operate so since this an erratic failure, check those connections. All of the other issues require a good front-to-back circuit between the controller and engine. I would start by separating the big harness plug at the engine and checking for corrosion. Clean it up and then connect/disconnect it several times. Now see what happens. If it still is not right, disconnect and clean the battery cable connections at both ends. Your symptoms point to a bad ground.

 

[dunk68]

Re: fuel gauge/tilt trim

I checked the plug and cleaned it well. Nothing happens. I also cleaned the ground on the motor and the battery.
I left the fuel gauge alone as I assumed if I had no ignition, the gauge doesn't get power anyway(powered by purple wire). So if I can find the ground problem, that should fix the fuel gauge.

I bought this boat last year, and something similar happened 1 time before. I cleaned the main plug on the motor and it worked fine until a couple of weeks ago. Someone mounted the battery at the front of the boat for a trolling motor and ran all cables at least 16 ft. from the motor to the battery. I'm going to move the battery back to the back tray on the pontoon. It appears that the cables are extended by adding a bolt and an extension cable to the front.
UPDATE****** Moved the battery to the back of the boat and ran new hot and ground cables and cleaned all terminals(both ends). Still won't fire the ignition. I ran the hot wire for the factory switch panel and once again, turning on the light allowed me to run tilt/trim, gas gauge worked, & the motor would turn over.

What do I check next?

There is no tilt/trim or tach plug in the controls. The wires are run individually to bullet connectors. Is there a ground wire I should check in the control box?

 

[dunk68]

Re: fuel gauge/tilt trim

I think I found the problem. After checking out all the connections on the ground and ignition wiring on the gauges, I reattached the battery cables and ran them to the motor through the housing and it started right up. It stopped 5 minutes later. I checked the wiring harness and have an open on the red and purple wire from the fuse to the center pin on the harness plug. Thanks for the help.