Extra gauge cutout

[compcrasher86]

I have an extra small gauge cutout and I already have tach and volt so I kind of want to get an engine temp. gauge for my ol' motor.

I have a 1987 Evinrude 140hp V4 (VRO). I can buy the gauge at my local marine supply store but I have no clue what else I need or how to hook it up. If somebody could lead me in the right direction that would be awesome. Thanks!

[Capt. Bob]

The gauge should come with everything you need except the wire. The sending unit will mount to the motor on top of one of the cylinder banks. You'll use one of the bolts that hold the head "cover' (don't know the correct term) in place on top of the head.
The sending unit will need to make good contact with the head so as to transfer heat to the unit.
You will need to run a wire from the back of the sender to the gauge. The instruction sheet will show which post (grn.) to connect this wire. Another will be the "power" and you should also have a post for lighting.
The sending unit acts as a thermal resistor (again this might not be the right term). As the engine temp increases, the sender's resistance decreases and creates a better ground (remember, the sender is in direct contact with the engine block) and the gauge needle moves to indicate the temp.

It's important that the sender is in clean contact with the engine. The instructions should be fairly straight forward and I'm sure someone will speak up to "clean up" any mistakes I've made.

Good luck and keep us posted.

[compcrasher86]

Thank you, a well written set of instructions indeed! Now I understand why the box at West Marine says Temperature gauge "Kit". Hopefully the instructions will be straightforward as to where to attach the sensor but it seems pretty simple, a good metal contact point on top of one of the cylinders. I will post if I run into any problems

[Capt. Bob]

Thank you, a well written set of instructions indeed! Now I understand why the box at West Marine says Temperature gauge "Kit". Hopefully the instructions will be straightforward as to where to attach the sensor but it seems pretty simple, a good metal contact point on top of one of the cylinders. I will post if I run into any problems

You got it. Scrape the paint off of the contact point on the head to insure a good ground.

Good luck.

[GoneFission]

If I had the choice between water temp and water pressure, I would (and have) go for a water pressure gauge.  You can see a water pump going south with a pressure gauge well before it causes a cooling problem and the engine overheats.  By that time, it's usally too late.  It's nice having both, but my vote is for water pressure over water temp, but that's JMHO.  

See ya on the water!

[compcrasher86]

I just went over my motor today to look for the spot to put the temp gauge in. I am not quite sure what you mean by head cover but I did see two strategically looking threaded holes on top of each side of each pair of cylinders. The threads and a small area around the hole are not painted so I imagine these are possible mounting points.

The thermal switch that grounds the engine alarm wire in the event of an overheat is in a similar looking hole on the side of one of the cylinders so I imagine I am on the right track.

It is pitch black right now and my camera phone doesnt have flash so I will post a picture tomorrow


I have considered a water pressure gauge but I am much more familiar with temperatures than I am pressure in general. Because I have an old motor, the water pressure coming out will probably remain consistent, but that is not to say it is adequate for running a V4 at 6000rpm (which I can but rarely do). Therefore pressure would appear normal but in fact "normal" may not be enough to cool an old engine at high RPM. Because of this, I would prefer to see a gauge that fluxuates with the amount of stress and power I put on my engine so I will know when to ease off throttle and give it time to rest.

[GoneFission]

If you are going with a temp gauge, consider dual senders.  Put a toggle switch in so you can switch between cylinder banks.  Put a temp sender on each head and you can tell if one side is running hotter than the other.  Normal on an OMC is about 140 degrees F. unless sitting and idling then it will go just a little higher.  

Good luck!

[compcrasher86]

Gonefission,

that is a great idea I never thought of that! I assume I could just use a On-On switch, put it next to the gauge or something, wire the sensors to that. I like that idea alot