Mechanical water pressure gauge, Merc 135

[Smokin'J]

I would like to install a mechanical water pressure gauge on my 1999 Merc 135 carb. I'm not sure where to either install a fitting or tap into one of the water hoses. I want an accurate reading on the gauge. Any help or a picture of where I need to hook up would be very appreciated.

Thanks, great site!

[FUJIMO]

This is the location where you install the fittings & pressure line for your particular water pressure gauge. This photo is to show only where the port is. The fittings & hose in the photo are a bit unusual. All you need first, is the proper size brass reducing bushing. Then thread into that, the proper size 90 degree fitting for your particular gauge size pressure tubing/hose. The hose connection(s) must never leak at the gauge, or water will travel up the line & ruin the gauge, especially in salt water. Conventional speedo's and water pressure gauges are air pressure gauges. Water is not intended to travel up the length of the hose/line. Hope this helps.

[Smokin'J]

Thanks for the info and picture. I'll have a look at my motor and hopefully figure it out. Is there a factory plug where I need to install the fitting or will I need to drill and tap?

[FUJIMO]

There is a factory, top of block, pipe plug, with a square recess hole in the top, that happens to be the same size as simply putting your 3/8" rachet wrench into, that allows you to unthread it out of the block. If someones been there before you, its anybody's guess what, if anything has changed. Using teflon tape, thread the proper size reducing bushing, into that port, that hopefully came with your "complete" gauge "kit". Then the 90 degree fitting, that came with your gauge kit. Then attach your pressure line, that came with your gauge kit, up to the dash, without kinking or crushing it, in any way. Absolutely NO drilling or tapping is ever needed on an outboard, when installing a gauge.

[Smokin'J]

Thanks again Fujimo, if you're ever in my neck of the woods stop in, I owe you a ride.

[FUJIMO]

[Smokin'J]

[QUOTE=FUJIMO;2939207]


I took a look at my motor and the port you have located for my water pressure already has what looks to be a 3/8 water line connected. It leads to the lower starbord side of the block. Can I simply install a "T" fitting in this line? thank again.

[XstreamVking]

That would do it....That hose goes to the poppet valve....