850 water pressure gauge

[hereto]

I have a 1976 850 Merc which I am about to install a 15psi temp gauge. My first thought was to install the line with a "T" to the pee tube. Was told it would be better to install the line by removing a plug from the block? I can't find a plug to remove, can someone point out where this plug might be.

Thanks in advance

 

[merc850]

Re: 850 water pressure gauge

On my 1975 850 it's a brass pipe plug on the port side of the block under the shift/throttle cables. The only way I can see to install the gage tubing is to lift the block up and replace the brass plug.

 

[Moody Blue]

Re: 850 water pressure gauge

I have a '71 Merc 800 and installed a pressure gauge a couple years ago. Tried "T"ing into the tell-tale line with poor results. Plumbed it directly to the water port on the water jacket cover and it works like a charm. I get 2-3 PSI at idle and 10-12 PSI at WOT.

The fitting on my '71 800 is located between the spark plugs of cyl's 2 and 3 (4 cyl). It is a brass 1/8" pipe plug fitting with a hex head.

 

[Chris1956]

Re: 850 water pressure gauge

Hereto, Some of those inlines have a plug, others don't. You want to use a plug on the cylinder head water jacket. If your motor doesn't have a plug on the cylinder head water jacket, buy a brass tee, and use it to replace the plastic telltale elbow. Now install the elbow on one of the ports and the gauge nipple on the other. It will work OK.

 

[hereto]

Re: 850 water pressure gauge

Thanks to all, The gauge works great, and the plumbing job was a piece of cake. Have attached a pic for anyone else who might need a bit of help hooking up a pressure gauge to one of these older Mercs.

Thanks Again
hereto

 

[Moody Blue]

Re: 850 water pressure gauge

Hereto, was that the original connection for the telltale that you "T"ed into or was the original telltale located at the base of the powerhead on the port side ?

I have mine plumbed similarly, pressure gauge off one side of the T and a temp gauge off the other side of the T. Telltale is original off the powerhead base on port side.

 

[hereto]

Re: 850 water pressure gauge

The brass "T" is where the original pee tube was located. There were no other place on the cyl head cover I could hook up to. worked out well.

hereto