temperature sender question

[NC State Guy]

1980 mercruiser 470 serial 5520896.

Got a new temp gauge and sender today. Wanted to replace old color code temp gauge with real numbers. The sender threads were too small so I left the old sender in to see if it worked. no dice. gauge got up to 130F, thermom in exhaust man got up to 165F. I looked on sierra for a sender, and couldn't find it for my engine.

question is does the sender have to be a teleflex brand, or is there an adapter that can be bought to make it fit?

thanks

 

[achris]

Re: temperature sender question

Merc gauges and senders are 33-240 ohm. If the new gauge is a 33-240 ohm gauge, it'll work.... These things aren't degree precise, they vary around a bit, and are really only an approximate reading, not a definitive one.

Chris.......

 

[NC State Guy]

Re: temperature sender question

Merc gauges and senders are 33-240 ohm. If the new gauge is a 33-240 ohm gauge, it'll work.... These things aren't degree precise, they vary around a bit, and are really only an approximate reading, not a definitive one.

Chris.......

Chris

Thx for the response. the ohm reading on the merc temp sender is around 75 when actual motor temp is 120F and gauge reads 120F(bottomed out). Shouldn't the ohms be 33-35 instead of 75? The gauge reads from 120 to 240.. so the ohm resistance to correspond should be 33-240?

I'm not an ohm expert, borrowed the multimeter from a friend..

Thanks

 

[achris]

Re: temperature sender question

It works the other way. As the engine gets hotter the resistance decreased. At 240? the resistance would be close to 33Ω. So when the engine's cold the resistance will be high....

I'd say that 75Ω at 120? sounds about right....

Chris.....

 

[Silvertip]

Re: temperature sender question

If the sender you have is too small for the threaded hole in the engine, go to your local home or hardware store and buy a reducer bushing.

 

[NC State Guy]

Re: temperature sender question

thx for the help guys. bouyght a multimeter tonight. will look into the reducing fitting if I can't find the proper sender. or i guess my sender may actually be ok. learn something new everyday with these boats...