how do i hook up a water pressure gauge, mercury 85hp 850

b0horman

Cadet
Joined
Nov 27, 2006
Messages
23
i have already tried to hook up my water pressure gauge and i am not getting any readings. What i did was "T" into the hose that my tell tale is connected to. Is there somewhere else i should be hooking it up?
 

chum1

Petty Officer 1st Class
Joined
Apr 15, 2010
Messages
359
Re: how do i hook up a water pressure gauge, mercury 85hp 850

one way is to get the 12-53491 tee, screw it in the water jacket where spark plugs are then run a plastic hose up to the panel with this gauge: http://www.jegs.com/webapp/wcs/stor...tId=763500&itemId=83664&langId=-1&showValue=1

It will read about 6 lbs at full power
iboats also has actual water pressure gauges if you want it to look more official, they must be about 15 lbs max to get a useable reading.
 

Moody Blue

Captain
Joined
May 24, 2004
Messages
3,136
Re: how do i hook up a water pressure gauge, mercury 85hp 850

I went thru the same learning process a couple years ago with my 1971 Merc 800. Tried teeing into the telltale with the same results, no reading.

I then installed a "T" fitting into the port on the waterjacket cover located between cyls 2 and 3. There is presently a 1/8" NPT plug installed there from the factory. On one side of the "T", I connected the pressure gauge and on the other side of the "T" I connected a temperature sender.

With a new impeller installed, I get about 3-4 PSI at idle, and at WOT I read 11-13 PSI. I also have a temperature gauge but these motors do not have a thermostat so they run REALLY cool and the gauge needle rarely moves off the peg.
 
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