Thermostat question

"Hi gang,
OMC 1978 240. Therm

"Hi gang,
OMC 1978 240. Thermostat wasnt reading anything. I verified 12v to the thermostat gauge and approx 4v on the sender screw. Also read 4v at the sender on the intake manifold. Fiddled with the ground post on the gauge as it felt a little "wobbly"?? and got the gauge to respond to about 100-110.. took the ground off and it jumped up to 125.. still seems low right? Im thinking I should be in the 160 range right? Im thinking this is a gauge issue and not a sender, are there any other tests I can do to verify.. or just buy a new gauge? Thanks.."

"What you can try is to take a

"What you can try is to take a jumper wire and go from ground to the sender post on the gauge, when you turn the key on it should peg all the way to the right. Normally this proves the gauge is OK and the problem could be the sender or even the wire between."

"Thanks Bob, Im going to try t

"Thanks Bob, Im going to try that on my next trip to the lake. Im curious also, does anyone know the size on the temp sender? Is it 3/8 or 1/2" sender for the 240 OMC? Im waiting for the manual Ive ordered. Thanks!"

"Still waiting for the manual

"Still waiting for the manual but from what Ive read online the manual doesnt say if its 3/8 or 1/2 inch sender. Id like to have the right one for my next trip up to the lake, anyone know which size it is on the 240 omc? Thank you!"