temp gauge

[inx7979]

I have a mercury 650 thunderbolt sn# 3810608 and is there a way I can install a temp gauge?

 

[Chris1956]

Re: temp gauge

Most of those old inline Mercs did not have thermostats. With no thermostat, the temp was all over th place from dead cold at idle to hot at speed. Your best bet is to install a water pressure gauge. Get one that reads 0-15PSI. You may see 15PSI at WOT, but probably not.

 

[inx7979]

Re: temp gauge

Where would I install it on the motor?

 

[Chris1956]

Re: temp gauge

Look for a small hex head plug on the head waterjacket. If you do not have one of these, install a tee in the place of the telltale elbow and one side of the tee is the telltale and the other side is the pressure gauge.

 

[Moody Blue]

Re: temp gauge

I tried the "T" into the telltale line option on a 71 Merc 800. Get 3PSI at WOT and the gauge shows 0 rest of the time. Brand new impeller and pump housing.

Hopefully today I will switch the connection over to the port on the head waterjacket and see what happens. If I don't get any better readings then the pressure gauge will be pretty much useless.

I also have a temp gauge installed that is connected to the head waterjacket port. My gauge range is 60-200 so I get a pretty good indication of the full operating temp range. Like Chris1956 states, the temp fluctuates all over the place but at least I get an indication of what the temp actually is.