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Bigbroadjumper
11-25-2016, 09:44 AM
I have been working for the past 6 months getting my '68 Donzi 18 back on the water. I replaced lots of parts including the water pump impeller. All new gauges, sending units, wire harness from dash to engine and all new connections. Now when I run the engine I can't get the engine temp over 100 to 110*. I replaced the thermostat... no difference... I replaced the gauge .... no difference. I removed the sender and put it in a pot of boiling water, grounded the pot to the block and the gauge showed it and the sending unit are working.

I'm stumped. Any ideas?

tmdog
11-25-2016, 05:08 PM
Are you running on the garden hose or in the water?

Bigbroadjumper
11-25-2016, 05:44 PM
Are you running on the garden hose or in the water?

Running both flush kit and in the water. I ran at 3k rpms for about a half hour and never got above about 110*.

Capevettes
11-26-2016, 08:44 AM
Have you tried to confirm the temp by shooting an IR gun at the thermostat housing when it's warmed up? I don't see how a warmed up engine could possibly run that cool. My guess is that the send unit is incompatible with the gauge.

tmdog
11-26-2016, 09:32 AM
Swap out the thermostat and use a IR gun to check temp at T-housing like Cape-- suggested. Somehow water is by-passing t-stat?:confused::confused:

mattyboy
11-26-2016, 12:02 PM
Bad ground at the gauge

mattyboy
11-26-2016, 12:21 PM
sorry the site doesn't like my new phone it sounds like a bad ground at the gauge or the sender end is there tape or sealant on the sender?
to test the ground at the gauge pull the sender wire off the sender turn the key on and hit the wire to a good block ground the gauge should peg

to test the ground at the sender get a volt meter red to + on battery
and the black to the sender collar should get 12 volts

mattyboy
11-26-2016, 12:25 PM
also what happens if you check that the intake is grounded?

Ralph Savarese
11-26-2016, 05:33 PM
also what happens if you check that the intake is grounded?
It appears he said he did that in his first post

mattyboy
11-26-2016, 07:02 PM
The way i read it the pot with the water was grounded to the block he didnt mention verifying grounds

HallJ
11-27-2016, 10:19 AM
Try adding a ground wire to the sending unit body. Ty rap, safety wire or small hose clamp to hold it there.

Jeff

mattyboy
11-27-2016, 11:24 AM
Try adding a ground wire to the sending unit body. Ty rap, safety wire or small hose clamp to hold it there.

Jeff

+1.......

HallJ
11-27-2016, 12:48 PM
Use your DVM to measure the resistance between the main engine ground and the body of the sensor where the hex is.
If it is more than two or three ohms, add the ground wire and measure again.

Make your measurements with the ignition off.
Jeff