Wiring up gauges

[um0RION]

NEW UPDATES 8-10-10

Im not sure if this is where this is supposed to be, but here goes.

I bought a 7 gauge set from ebay, with only the gauges, no sensors. I got a speedometer, tachometer, fuel gauge, trim gauge, oil pressure, water temperature gauge, and a volt gauge. ($63 total shipped, yay!)

Right now my boat only has a speedometer, and a fuel gauge. I know how to hook up the battery volt gauge (haha) and I will swap the old speedometer and fuel gauge for the new ones. The other stuff though, I have no idea about. Basically that means I need to find out how to wire in the trim gauge, water temperature gauge, tachometer, and oil pressure gauge. I know how electricity works, so positive negative and ignition power is no problem, I just need to find out how to get the gauges to display the right data. Can anyone help me out with this?

I have Faria gauges, if that helps any. My trim gauge says "Mercury" on it so Im not expecting that one to be able to be used, but if it is, great

 

[Bifflefan]

Re: Wiring up gauges

I'd say go to Faria's web site and ask them for a wiring diagram. Then also get the sending units for their gauges so they read correctly.
Then put them in following the diagram.

 

[Silvertip]

Re: Wiring up gauges

If this gauge set is for an outboard, you have no use for an oil pressure gauge because two stroke motors don't have oil pressure. Four strokes do though. Of all the gauges you mentioned, oil pressure, fuel and the trim gauge require senders. They are all wired exactly the same. Each gauge requires +12 volts when the key is on, ground, light, and sender (the "S" terminal on each gauge). The tach requires a connection to the ignition coil if you have an I/O or to the charging system if you have an outboard. They are different tachs by the way so I suspect you bought an I/O gauge set. If you have an outboard, the tach is wrong. The fuel gauge uses the same sender you currently have. Oil pressure (if you can use it) requires and oil pressure sender to match the gauge) and the trim gauge requires a trim sender for your specific engine or outdrive. Water pressure does not require a sender since it operates just like the speedometer. A small hose connects it to the water pressure port on the engine. If we knew exactly what type boat (outboard, two stroke, four stroke, I/O, 4, 6, 8 cylinder) we could be of more help. Go to the very top of this forum and look at the sticky titled "Generic Boat Wiring Diagram".

 

[um0RION]

Re: Wiring up gauges

If this gauge set is for an outboard, you have no use for an oil pressure gauge because two stroke motors don't have oil pressure. Four strokes do though. Of all the gauges you mentioned, oil pressure, fuel and the trim gauge require senders. They are all wired exactly the same. Each gauge requires +12 volts when the key is on, ground, light, and sender (the "S" terminal on each gauge). The tach requires a connection to the ignition coil if you have an I/O or to the charging system if you have an outboard. They are different tachs by the way so I suspect you bought an I/O gauge set. If you have an outboard, the tach is wrong. The fuel gauge uses the same sender you currently have. Oil pressure (if you can use it) requires and oil pressure sender to match the gauge) and the trim gauge requires a trim sender for your specific engine or outdrive. Water pressure does not require a sender since it operates just like the speedometer. A small hose connects it to the water pressure port on the engine. If we knew exactly what type boat (outboard, two stroke, four stroke, I/O, 4, 6, 8 cylinder) we could be of more help. Go to the very top of this forum and look at the sticky titled "Generic Boat Wiring Diagram".

Ok good points... I have a 2 Stroke 4 cylinder Evinrude outboard, 120hp, 1991. Being a 2 stroke motor, you say that an oil pressure gauge is useless? Its a VRO engine, if that matters.

So for me, the oil gauge probably cant be used, I can use the water temperature ** (not pressure) gauge, fuel gauge, speedometer, volt gauge, the trim gauge will require a sending unit specific to my motor, and the tachometer I have might be useless since on the side of it it gives instructions for calibrating it for 4 strokes, and engines with a 12 pole alternator (which I dont know if mine has?)

 

[Silvertip]

Re: Wiring up gauges

Your motor does have a 12 pole alternator so the tach will work. If there is a 6P (6 pulses) setting that's the one you need. If there is a "Water Pressure" guage you can use that as well. This is not an electrical gauge as it simply measures water pressure from the water pump. You tap into the tell tale hose with a "T" fitting. Yes -- you have an "oil injected" engine but it is a two stroke. Two strokes do not have pressurized lubrication systems like a four stroke or car engine. The VRO merely mixes the oil with the fuel before it enters the engine. No pressure involved that you could read on a gauge. The water temperature gauge requires a sender of 33- 240 ohms resistance which may be very different than the sender for an I/O. I/O gauges are typically calibrated 120 - 240 degrees. The bad part about those gauges is the needle will be on 120 degrees most of the time since outboards do not run as hot as 4-strokes. A gauge calibrated with 60 or 100 degrees on the low end is more practical. Except for oil pressure, it looks like you can use the rest of the instruments. There is a "Generic Boat Wiring Diagram" in the stickies at the very top of this forum. Here is how I connected the water pressure gauge on my Merc triple.

 

[um0RION]

Re: Wiring up gauges

Ok, sorry for the lonngggg time between posts, but Im getting the boat ready for water, and it needs a tachometer before Ill take it out.

I dont have any gray wires hanging anywhere that would be the tachometer. However, on the side of my controls under the ignition, there is a black pulg which currently has a purple wire coming from it. This is the only place I could see that might have a tach wire attached. The purple wire is ignition power im pretty sure, and on the box there are 2 more unused pins.

Somewhere I read about a harness where one wire was ignition power, a ground, and the tachometer. Might this be what Im looking for? Id have to put another pin in the black plug I have, but thats no big deal. Am I looking at the right thing? I checked the tach section of the service manual, but couldnt find anything about it. Ill post a pic..

 

[um0RION]

Re: Wiring up gauges

Another long time between updates, I took the boat out a couple times without a tachometer, and Im getting to the point where I really want one, to be sure im operating in an optimal range, and not losing out on speed/power due to the effect of the prop pitch on engine rpms.

Is there a number for the harness that attaches to the plug on the controls? It has 3 pin holes, if that matters. I know one of the three is the tach for sure. Ive seen plugs with 5 pins, and I dont think that will work at all.

Is that the only place to get the tach? There's another harness under the dash with a couple cut off wires, and I think one of them was used. I didnt pay it much attention since it didnt have a solid gray one in there, but is it possible it could be for a tach? No other gauges besides the speedo and the gas gauge has ever been installed, so...

 

[Silvertip]

Re: Wiring up gauges

That three pin plug is for connection of a tach. Check here on IBoats for the tach harness. If they don't have it, Cabelas does.