Tinkerboater

Then what you are saying is as the alt. increased or decreased the voltage the gauges will change their reading? When engine is not running battery voltage of a fully charged battery with no surface charge is aprox. 12.7v. When alt is putting out voltage is anywhere from 14.4-13.5 volts based on state of charge of battery, temp, & a few other varables.

I have been wrong before, but I thought when I turned on the iginiton the gauge would go to the lowest point if I had wire connected to sending unit or not. When I get in boat tonight I will have to try it.

HMmmm, I should have read Fouls original question more closely. Tinker is right. But how would turning on the Nav lights affect the engine guages? They are effectively a seperate circuit. ?? Id like to drag my Simpson over there and have at this one. Sounds interesting.

The guage cluster uses power fed from the key switch. And the nav light s probably feed from the same power wire or fuse block.The slight difference in voltage from when the engine is off to when it is on will not usually make a difference in the guages. With everything turned on FOUL probably has 9 to 10 volts at the guages instead of 13.

TURBO -- when I turn on my ignition keys my guages read what the pressures and temperatures are at that time. Same for drive possition and volts. Fuel level reads the amount of gas in the tank also. The engine doesn't have to be running for all your guages to work.

Tinker- I agree with when engine is on or not gauges read what the condition is at that time. What I was trying to say is (& did not do a good job at it), take the oil pressure gauge, when key is off needle could be anywhere on scale. When key get turned on with engine off gauge will go to "0" oil pressure. I am thinking that gauge goes to "0" if the sender wire is connected or not. If I am correct, then the gauge does need ground. Otherwise gauge would just stay where ever needle likes sitting at if the sender wire is off.

formula31- Wish boat was closer to me so I could see exactly what problem is.

Foul- Do you have a volt meter on dash? When lights are turned on or off what is it showing in voltage?

Turbo --- the sender wire is the ground. If you remove the wire it will read 0 --if you short it to the engine block ( ground ) it will read full scale. This same process works with the engine temp also. The sender has a reverse acting variable resister in it -- as the temp or pressure goes up the resistance goes down ( more ground) gas tank sender works the same way.

Tinkerboater - Just got home & checked out my gauges (eliminator brand??) Needle on water temp was at 200+ mark. disconnected wire going to water temp sender. Turned iginition on, gauge then went to all the way down. Reconnected temp sender wire & gauge moved up to 100 (temp in garage). I did not disconnect ground wire at gauge because too hard to get to. If the ground was not used by the gauge at all, the gauge would not have gone to the lowest point with the sender wire disconnected when power was applied to gauge. I am not saying all gauges need ground just ones I have in my boat.

Most boats with stock guages--The needle will be at 0 with the power off.

Waterfoul;
In your earlier post, you said your navigation lights were causing the problem, in a later post, you said your docking lights. Which is it? The nav lights don't take much current and your problem is probably in the plus wire to the dash (per tinker boat). If you have your docking lights on the dash curcuit, you are overloading the wire and the voltage starts to drop. You need to run an independent circuit with sufficient capacity.

Foul-
I was trying to give you a general troubleshooting technique- it does not matter if you have fuses or breakers. Start at the end and work your way back to the battery. Whatever you do, don't let the smoke out, it makes all that stuff work.

I have an issue of hot boat(?) about 4 years old with the foul in it!

Tinker-
You are probably right, but I would still do a complete check of the system. I have seen bad connections do some strange things- and he may have more than 1 problem.

It would be kinda nice if you told us what you found. After all, a lot of people responded with suggestions. You don't even answer back. What is with that?