i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

[shackdadde]

heres the story. 1985 bayliner ciera 24ft. 305 engine. i just bought it and put her in the water.TEMP GAUGE does not work so i grounded the sending unit wire and the guage went hot so i then thought the sending unit was bad.replaced the sending unit.same problem.i measured the volts at the sending unit wire to the grond at the battery and intake to make sure i have ground and i get 7 volts. i measured the sending unit wire at the gauge and get 8 volts i figure voltage drop. i measure the power feed to the gauge and i get 13.8 when running.so assume there is something wrong with the gage so i go to the local boat boneyard find a used matching gauge for 10 bucks i throw it in and the same thing happens.i highly doubt that the second gage is bad but it may be possible. so im at a loss for testing and trouble shooting so i thought id ask the pros what they thought. well what do you think. asap lol i want to go out this weekend. thanks in advance

 

[bjcsc]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

Who is the manufacturer of the gauge?

 

[shackdadde]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

stock bayliner gauge does no say on it

 

[Don S]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

I would check the gound wire for the gauge. No ground the gauge won't work.
Could also be that the engine is running below 100° where most gauges start. Might check fpr a thermostat.
Might also want to check the continuity between the sender body and the intake manifold. High resistance there would show as low reading on the gauge. You don't want to use any teflon tape on senders.

 

[ron7000]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

run the boat, if you see steam or hear knocking then you're overheating. temp gauges are overrated anyway.

you could take an ohm meter if you got one and measure the sender on the engine. When cold it has high resistance. When hot is has lower resistance. It'll depend on the sender but most range from a few hundred ohms to 50 or so for 100-180F.
you could also get a few packs of resistors from radio shack for a couple bucks and test the guage sender post to ground thru a known resistance. Try 10-20-50-100-200-500-1k ohms and see if the gauge responds in the expected way. Could also buy a potentiometer or rheostat (variable resistor) and turn it to watch the gauge move. Get whichever is cheaper. Get a POT or rheostat that is linear taper as opposed to audio taper and goes to 1k or 5k. If they only stock ones higher than that get the lowest one, you want one that'll give you resolution in the 10-500 ohm range. otherwise when you turn it the guage will just jump from cold to hot and not hold at any value in between.

 

[whywhyzed]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

Most 12V gauges have a voltage regulator circuit in them that drops the sender wire voltage to 10 or so Volts. They don't send the full supply voltage, because the temp would fluctuate as your alternator charged the battery...
I've not seen 7, but it could be right.
Did you put sealant on the threads of the sender?
Wipe it off- the threads are the path to ground!

 

[shackdadde]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

did the resistor trick and put 50 ohms and it reads 180 so i put 100 ohms and it was 120 so i know the circuit is good. new temp sender onmn it so i thought the engine may not be getting hot enough ran it hard and it feels hot enough to not beable to hold my hand on the t stat housing for more than 10 seconds.is it possible that my sender being near the t stat is getting cold water????????????????????????

 

[whywhyzed]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

could be the wrong sender for that gauge.
They are a matched set.... sorta...
140F is uncomfortable to hold on to so sounds like the temps are coming up.

 

[jerryb1]

Re: i got 7 volts !!!!!!!!!!!!!!!!!!!!!!

did the resistor trick and put 50 ohms and it reads 180 so i put 100 ohms and it was 120 so i know the circuit is good. new temp sender onmn it so i thought the engine may not be getting hot enough ran it hard and it feels hot enough to not beable to hold my hand on the t stat housing for more than 10 seconds.is it possible that my sender being near the t stat is getting cold water????????????????????????

Try taking out the sending unit, hook up a couple of clip leads and an ohm meter. Then put it in a pot of water on the stove and bring it to a boil. See if the resistance matches up as you expect. Great way to check thermostats also.