1978 140hp Mercury Temp Monitoring Options

[stephenspann27]

I am trying to decide how to monitor the temperatures on my '78 mercury outboard. There is a hole near one of the spark plugs for a sending unit. I do not have a sending unit. I have found an alarm (speaker) for sale with a two wire pig tail hanging out of it. If I purchase that, will I only need to find a brass sending unit? I haven't been able to find one so far. If I buy both of these for close to $100, I'm wondering if it might be better to just buy a digital setup like "TM1" from Austrailia :
http://www.ebay.com/itm/OUTBOARD-MO...Parts_Accessories&hash=item20e4ef5e59&vxp=mtr

Thoughts?

 

[Faztbullet]

A Inline runs to0 cold for a guage to read, that hole is for a overheat sensor..

 

[stephenspann27]

I don't see how too cold would be a problem for an electronic gauge like I listed. I would use the OEM mercury stuff if I could find a sending unit.

 

[Faztbullet]

It will work but unit will ready cold at idle and warmer at WOT so be careful where you set alarm so you get no false readings