1986 gauges

[Fish247]

I have a 1986 Mercury 150 XR2. I’m in the process of restoring the boat and would like to replace the gauges. I’m fabricating a new gauge cluster, so any size/style is fine. the engine only has 3 gauges, Tach, Temp and pressure. I’m guessing the pressure is for water. Anyway, are all gauges compatible with this motor, or do I need specific gauges Unique to Mercury or this particular motor? Thanks!

 

[Faztbullet]

Any gauge whether OEM or aftermarket made for a outboard will work. All you need is tach,pressure and fuel

 

[Chris1956]

You will want a 0-15PSI water pressure gauge, 0-7000RPM gauge, a speedometer and a fuel gauge, IMO. Choose a set that is for outboards, and it should be compatible with your motor.

The water pressure gauge fitting can be plumbed into the powerhead at several locations. See what works for your particular motor, as the hoses changed over the years. There also may be a threaded plug you can replace with the water pressure nipple.

Your motor may have the speedo pitot built into the gearcase. My '88 Merc 135HPV6 does. That makes it convenient.

 

[airshot]

Water pressure gage is a new one for me, been around boats for 60 plus years but mostly small outboards, never saw the water pressure gage used. What is it for, how does it work??

 

[Chris1956]

Water pressure indicates how well your impeller is cooling the motor. Impellers wear and loose pressure. Much better than a water temp gauge on Outboard motors, IMO

 

[QBhoy]

You will want a 0-15PSI water pressure gauge, 0-7000RPM gauge, a speedometer and a fuel gauge, IMO. Choose a set that is for outboards, and it should be compatible with your motor.

The water pressure gauge fitting can be plumbed into the powerhead at several locations. See what works for your particular motor, as the hoses changed over the years. There also may be a threaded plug you can replace with the water pressure nipple.

Your motor may have the speedo pitot built into the gearcase. My '88 Merc 135HPV6 does. That makes it convenient.

Hi Chris. Just read your reply there. Is that all the psi range needed on those engines ? Didn’t know they ran that low a pressure. Very low compared to the 2016 merc 2.1l I have. That shows about 15 psi just at idle.

 

[Chris1956]

Those old V6 Mercs do have low water pressure. The poppit valve opening at about 2000RPM may limit water pressure.

Alternatively, my Johnny 150HPV6 runs at 30+PSI.

 

[Faztbullet]

You need a 30 psi gauge as it will be 5-10psi at idle, and 18-22 at midrange with poppet cycling and 12-18 psi at 5K. A 15psi is for inline engines

 

[Fish247]

Thanks for the feedback. The gauges I purchased came with a 0-30 psi gauge so hopefully it works.

 

[Fish247]

So I have another question. Pictured above is the back of the old tach and the new tach. Since a 1986 Mercury 150 is 6 cylinders, do I point the little arrow to the #2? I’m a little confused because of where the old one is set.

 

[Fish247]

View attachment 376563View attachment 376564
So I have another question. Pictured above is the back of the old tach and the new tach. Since a 1986 Mercury 150 is 6 cylinders, do I point the little arrow to the #2? I’m a little confused because of where the old one is set.

 

[Fish247]

Pic of the old tach before wires were removed

 

[dwco5051]

Set at #5. Your wiring set up measures alternator pulses not ignition.