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Old 10-05-2010, 03:46 PM
Luv2Ski's Avatar
Luv2Ski Luv2Ski is offline
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Boat: 1988, ProStar 190, 351w
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Temp gauge reading increases when accessories powered up

Hey folks,

My prostar typically runs around 170 deg, gauge in general appears to work as it should.

However, with each accessory I power up the engine temp reading will increase by about 5 degrees. So, if I switch on the bilge, it will it 175, lights 180, heater and I am pushing 190.... etc. This works both ways (switch them all off and temp instantly back to normal).

Clearly this just has to do with the increased electrical draw and not actually a change in engine temperature. Not really a concern per say, but it is a bit unsettling when the high temp alarm goes off (I am compelled to turn off the accessories even though I know it is a false reading).

Is this normal? If not, any suggestions?

THANKS!

88 Prostar 190, 351w
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  #2  
Old 10-05-2010, 03:54 PM
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thatsmrmastercraft thatsmrmastercraft is offline
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My guess would be a bad ground for the temp gauge.
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  #3  
Old 10-06-2010, 08:18 AM
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Before I can give any suggestions, I have a few questions:

#1 Does your temperature gauge work correctly at all other times? It starts at the
maximum cold position when it's first started and then moves to the 170 degree point?

#2 What do the other gauges do when this happens?

#3 To verify your gauge wiring, remove the tan wire from the temperature sending unit and
see if the temperature gauge drops to the cold position.
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  #4  
Old 10-06-2010, 10:48 AM
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Luv2Ski Luv2Ski is offline
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Quote:
Originally Posted by thatsmrmastercraft View Post
My guess would be a bad ground for the temp gauge.
Connection to the sending unit is clean. I should remove the unit and clean both sides of the threads and see if that helps. I tightened all the gauge connections when I had the dash out a few months ago, so pretty sure it is all good on that end.
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Old 10-06-2010, 11:06 AM
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cbryan70 cbryan70 is offline
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my old boat does this as well. When i turn the blower on i lose a quarter tank of gas. Always fun when at idle i forget I have the blower on and think ive gone through alot more gas then i should then realize its on and turn it off
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Old 10-06-2010, 11:19 AM
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Luv2Ski Luv2Ski is offline
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Quote:
Originally Posted by ahhudgins View Post
#1 Does your temperature gauge work correctly at all other times? It starts at the maximum cold position when it's first started and then moves to the 170 degree point?
Yes, works exactly as one would expect at all other times. I suppose I don't know for certain that the readout is correct when it runs at 170, but that seams in the ballpark to me with a 160 deg thermostat

Quote:
Originally Posted by ahhudgins View Post
#2 What do the other gauges do when this happens?
When an accessory if first switched on I may see a brief very bounce in the voltmeter, maybe the oil pressure gauge as well, but I believe they will quickly read normal after that. I will verify next time I am in the water.

Quote:
Originally Posted by ahhudgins View Post
#3 To verify your gauge wiring, remove the tan wire from the temperature sending unit and see if the temperature gauge drops to the cold position.
I will do that next time I get to the water, which should be this weekend. Given that the gauge reads more or less correctly I suspect the wiring is correct but certainly worth investigating.

Thanks
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  #7  
Old 10-06-2010, 11:23 AM
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Quote:
Originally Posted by cbryan70 View Post
my old boat does this as well. When i turn the blower on i lose a quarter tank of gas. Always fun when at idle i forget I have the blower on and think ive gone through a lot more gas then i should then realize its on and turn it off
Interesting that you have the same symptom on a different gauge. Do any of your other gauges change?
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Old 10-06-2010, 01:55 PM
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190 Skier 190 Skier is offline
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False Alarms

My 1990 PS 190 does the same thing. Worse is when I plugged a spot light into the Aux port and it immediately jumped to 220 degrees with the alarm going off. That is very unnerving when it is dark and you are trying to navigate a strange lake looking for a houseboat. I thought I was toast until I finally figured out what was going on. It all turned out good and just got back from 4 days of glass on Lake Shasta, did not see one other skier or boarder the whole time! Anxious to know if anyone knows how to correct this.
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  #9  
Old 10-06-2010, 03:12 PM
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It is very common to see all of the gauges drop (go to the left) when more accessories are turned on, especially in older boats. The gauges have one side connected to 12V and the other side connects to a sensor that acts like a variable resistor to ground. It only takes a small resistance change to see a change on the meter. If you have any bad connections in the meter circuit, you will have less current flow and the meter will have less deflection (moves to the LEFT). Also, if you turn on a blower or a large flood light, your battery voltage can drop 1 or 2 volts and this also causes less current to flow through all of the meters.

I used to own an 87 Prostar and I fixed this problem by rewiring my dash. The wiring behind my dash had a bunch of those crimp connectors between the gauges. I installed two terminal strips under my dash; I connected one strip to the 12V from the ignition switch and the other directly to the battery ground. I then removed all of the crappy wiring between the gauges and ran a 12V wire and a ground wire to each gauge. Problem solved. I can hand draw a picture of what I did and post it since I donít have the boat any more.
I have a theory as to why one gauge deflects MORE, but I would have to get some one to test it with a voltmeter. I think rewiring the dash would fix that problem as well.
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  #10  
Old 10-06-2010, 03:27 PM
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03geetee 03geetee is offline
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My boat does this too, not to bad though just a little movement when I activate the blower or bilge.

JTR
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