1971 Merc 800 Temp and Pressure Gauge install

[Moody Blue]

Setting up this new to me boat and motor. Would like to connect both a water pressure gauge and water temperature gauge.

The block has a plugged threaded port on the head located between cyl 2 and 3. Can I install a "T" in the head then install a temp sender unit on one side of the "T" and the tubing for the pressure gauge on the other side of the "T"?

Is there a better alternative?

Is the pressure gauge tubing capable of handling the hot water from the head?

 

[Moody Blue]

Re: 1971 Merc 800 Temp and Pressure Gauge install

Anyone else installed these two gauges?

Words of advice?

 

[This_lil_fishy]

Re: 1971 Merc 800 Temp and Pressure Gauge install

I dunno, but for the cost of a T connector it's definately worth a shot. It couldn't do any harm at least.

Ian

 

[Chris1956]

Re: 1971 Merc 800 Temp and Pressure Gauge install

Moody, The pressure gauge is an excellent idea. The water temp gauge will not be too useful since those motors do not have a thermostat and run dead cold at idle and hot at WOT.

 

[Moody Blue]

Re: 1971 Merc 800 Temp and Pressure Gauge install

"The water temp gauge will not be too useful since those motors do not have a thermostat and run dead cold at idle and hot at WOT."

Have to disagree about the temp gauge. Last motor, a 1993 Mariner Magnum 40 (Merc), I installed a temp gauge and found just what you explained, cold most all the time. Gauge barely moved. BUT, once last summer was boating in heavy weeded area and looked at the temp gauge and the needle was up past halfway on the dial, very hot.

Had it not been for the temp gauge I might have cooked the motor. Weeds had partially or completely blocked the water intakes.

Even if the needle sits on the lower peg most of its life, there may be that one time where it could save the motor.

I'm still going with both gauges. So, can I install both from the same port?

 

[SeaKaye12]

Re: 1971 Merc 800 Temp and Pressure Gauge install

If your temp gauge is a water immersion type, I doubt it would be very accurate unless it is mounted right into the block somewhere; not on a tee. I've seen posts here where people describe drilling and tapping into the water jacket to mount a gauge. It was not something I felt qualified to attempt so I never made notes of exactly where it would be done.

I have also seen temp gauges with senders that surface mount on the block....

But; as you say; you'd be looking for an unusual readout on the gauge....not any particular number.

It would be nice to have a gauge with an accompanying audible alarm so as to give you a better chance of noticing an abnormal condition in time.

Chuck

 

[Chris1956]

Re: 1971 Merc 800 Temp and Pressure Gauge install

Moody, It is your boat, install any guages you would like.

BTW - The water pressure gauge would have caught the weeds in the intake the moment it happened. You would not have had to wait for the motor to overheat.....