Water Press and Fuel Press guages

[signpro]

Where is the best place to tap in for the water pressure guage on a 2.5 merc? How about the fuel pressure, in the main fuel line from pump?? one more question, has anyone had a problem with a pressure line running to the mechanical fuel press guage?? are you using a guage isolator? What about the Gaffrig electric fuel press guages?? thanks for the help!

[Arizona Hotboater]

For the water pressure, I have had motors with 2 different pickup locations. One was on a fitting behind the flywheel and between the cylinder banks, the other is from a fitting plumbed into the top of the exhaust divider. Both worked well. My 2.5 has the exhaust divider plumbed with a fitting.

For fuel pressure, fit a T fitting close to the carbs, or fuel rail, because thats where the pressure needs to be correct.

I like electric fuel pressure gauges because you dont run the risk of spraying fuel under the dash if the plumbing fails. As long as you check its accuracy with a mechanical gauge, it should work fine. I dont run one on my boat but I did on my street rod.

I hope this helps.

[Techno]

If you run a mechanical fuel pressure gauge and buy an isolator you've just spent the money that could have bought an electric one- pretty close.

If your not going to get an isolator get the PROPER line. It has to be fuel proof. You can get it from Mcmaster-Carr(maybe rick racer?). They carry fuel proof hose for this pressure and line size. Your still pumping fuel up to the dash so still have this hazard. Hoses can abrade and age so this isn't a total fix. Hard lining from the dash to transom is a partial fix but then is probably the cost of an electric unit.

[Firestarter]

Run mechanical, the electric fuel psi gauges are useless. The gaffrig units work well. I use 1/8 inch ID line that is flame resistant, I tap the brass 90 degree fitting at the bottom of the fuel rail.
Water psi of the top of the head.

RT