Auxillary temp gauge

[Sink My Boat]

My boat is a 1988 Imperial, repowered with a 2004 Inmar 5.7 GM matched to a Volvo AQ 290 leg.
This boat was in storage for 2 seasons before this year, and I thought I could ignore a few things. Impeller, and water pick up tube.. One was corroded ( water pick up tube housing looks like a thermostat housing just below the gearcase. This engine set up has a San Juan Engineering closed system on it. ( Their customer service rep informed me they don't make a system for Inmar engines. But I digress. )
I overheated on the first shakedown run of the year. No harm done. Found the offending part. Replaced the impeller, hoses belts, thermostat. Coolant.
And started her up as soon as repairs were done. Worked fine except no reading on temp gauge.Tried everything. New gauges, sender. All manners of trouble shooting. Found a major short on the process, and a bad ground which caused all gauges to stop working, and make the temp gauge work.
At that point I bought the boat to a Volvo shop, and let them have a go at it. I got tired of smacking my head against the wall. Got the boat back, all gauges were working again, except temp gauge. This was again, a new gauge with matching sender.
I have given up. I now just carry a temp gun with me and baby the engine, and check the temp every few minutes or so. As you can imagine, not much fun, and limits how far I want to travel. My temps have been consistently running 140-150 on the gun...a little cool for a new 160* stat.
Ok...now that I have rambled, my question is this. I want to install a second temp gauge somewhere around the helm.
Can I run a hot lead to the battery, run a ground wire somewhere so I can get a good ground, and run a wire from the sender to the gauge?
I have given up and the dash mounted gauge, but want a working gauge. I have lots of teak and seaboard around around., so I can make a little cabinet for it.
Will my idea work? I would add a fuse, and a switch to cut power to the gauge when not needed.
Suggestions? Feedback? Input?
Again.. separate gauge...hot lead to battery....ground wire to good ground....new sender wire to sender post. Should work?

And am I cracking up, or is my sender the brass sender in the manifold?? Near the T stat housing

 

[alldodge]

My boat is a 1988 Imperial, repowered with a 2004 Inmar 5.7 GM matched to a Volvo AQ 290 leg.
This boat was in storage for 2 seasons before this year, and I thought I could ignore a few things. Impeller, and water pick up tube.. One was corroded ( water pick up tube housing looks like a thermostat housing just below the gearcase. This engine set up has a San Juan Engineering closed system on it. ( Their customer service rep informed me they don't make a system for Inmar engines. But I digress. )
I overheated on the first shakedown run of the year. No harm done. Found the offending part. Replaced the impeller, hoses belts, thermostat. Coolant.
And started her up as soon as repairs were done. Worked fine except no reading on temp gauge.Tried everything. New gauges, sender. All manners of trouble shooting. Found a major short on the process, and a bad ground which caused all gauges to stop working, and make the temp gauge work.
At that point I bought the boat to a Volvo shop, and let them have a go at it. I got tired of smacking my head against the wall. Got the boat back, all gauges were working again, except temp gauge. This was again, a new gauge with matching sender.
I have given up. I now just carry a temp gun with me and baby the engine, and check the temp every few minutes or so. As you can imagine, not much fun, and limits how far I want to travel. My temps have been consistently running 140-150 on the gun...a little cool for a new 160* stat.
Ok...now that I have rambled, my question is this. I want to install a second temp gauge somewhere around the helm.
Can I run a hot lead to the battery, run a ground wire somewhere so I can get a good ground, and run a wire from the sender to the gauge?
I have given up and the dash mounted gauge, but want a working gauge. I have lots of teak and seaboard around around., so I can make a little cabinet for it.
Will my idea work? I would add a fuse, and a switch to cut power to the gauge when not needed.
Suggestions? Feedback? Input?
Again.. separate gauge...hot lead to battery....ground wire to good ground....new sender wire to sender post. Should work?

And am I cracking up, or is my sender the brass sender in the manifold?? Near the T stat housing

Your not cracked up and I don't understand as with you why the current setup does not work. Only thing I can thing of is the wiring is messed up some how. You should have 12V to the gauge and ground, then a wire to the sensor installed on the thermostat housing. You could run from the battery to a fuse but how will you disconnect power when you shut the motor down. Get the volt meter back out and find out why your current gauge is not working

 

[Sink My Boat]

Got 12.5 V going to the gauge. Short out the gauge pegs the needle. Short the sender, pegs the needle. I dont have a sensor in the thermostat housing because its a closed system. San Juan Engineering. It has it's own housing. It doesn't use stock housing. Gauges jumped to the temp gauge have power so power is passing through.
The only oddball thing is, the sender has a black wire coming off of it, the gauge sender post has of course a tan wire. .We all have at one time or another patched wires together with whatever was handy. I did however remove the black wire, and run a wire directly from the sender to the gauge. No change.
Is it possible a brand new sender, matched to the gauge is no good??
Gauge was working before she overheated. All I can think of is when I was pulling hoses through transom while replacing parts on drive, I broke a wire? When I dropped the alternator to change the belt, broke a wire? I'm at a loss. I truly have tried everything.
This boat was bought from an estate. engine and drive were meticulously maintained. electrical wiring looks like a plate of spaghetti. Want to guess what my winter project is going to be?
As far as fusing the aux temp gauge, I was going to go with 1.5 or 2 amps, and then you know we all have that box of parts we hoarded through the years. I was going to put a nice light up rocker switch on the gauge.
Plus I cut battery power anyway when boat is not in use. its trailered.

 

[kelleyja]

Is it possible a brand new sender, matched to the gauge is no good??

It's possible, I always test these before I put them in. You need a multimeter with an Ohms setting, this will let you test the sender and the wire. My suspicion is that your sender wire has some corrosion around the terminals that is increasing the resistance to a range where the gauge won't work.

TO test the sender: test the resistance between the top stud and the threads at room temp - should be around 200. Dunk the sender in boiling water, remeasure, resistance should be LOWER around 30

TO test the sender wire: disconnect the ring terminal from the sender and jumper it to the (-) battery post. Disconnect the ring terminal at the gauge, connect it to one lead on your multimeter. Connect the other multimeter lead to the negative (-) bus. Read the resistance. If is anything over a couple of ohms you've found your problem.

If it were me, I'd run a new sender wire rather than a whole new gauge. The 12v power can be dirty, the gauge will probably run on 9-16v. The sender wire is very important to have exactly right.

 

[Sink My Boat]

its been a while since I posted to this subject, but I do have something to add. I mentioned I have a San Juan Engineering closed cooling system installed.
I have found instructions to the installation of the system, and it says to remove "both" temp senders from the intake manifold.
I have replaced one sender...the new cooling system has a nipple installed in the place of the "other" sender.
The "other " sender installs into this nipple. Could I possibly have been spending all my time and effort replacing and troubleshooting the wrong sender?
This other sender is, if I am facing the stern, with the front of the engine right in my face just to starboard of the thermostat housing. The sender and wiring I have been putting all my effort into in on the port side.
No mechanic has been able to tell me why I have two temp senders.
I may have to put another call into San Juan Engineering.
Can somebody here possibly enlighten me? Thanks in advance

 

[Bondo]

No mechanic has been able to tell me why I have two temp senders.

Ayuh,..... There shouldn't be two Sensors,....

There might be a temp sensor, 'n a temp alarm Switch,....

 

[dypcdiver]

Bondo is correct, normally on a VP engine the one on the T'stat housing is an overheat alarm switch Part No. 3850397 and the temperature gauge sender is mounted on the Stbd side of the inlet manifold Part No. 3852029 or Dual station 872068.