RPMs not working, what should I check?

[Glastron Boater]

Finally got to take my boat out. RPMs are not reading, and speedometer didn't work right away.

How can I check the signal wire from the outboard to the gauge?

What wire should it be?

Force 125, I believe it's a 1987.

Speedometer didn't work roof away. But it started working after a bit. Temp sensor also seems inoperative, but I know the gauge works (tested by grounding the wire to gauge, it jumped around when grounded), so I'm assuming sending unit at this point.

Gas gauge worked and seemed right.


How can I test the gauge itself or where does it pick up its signal from?

 

[jerryjerry05]

Retighten the screws on the bar where the cable hooks to the motor.
​Then unhook the tach connector on the back of the tach.
WD-40 in the connector.
​Push it on and off a few times.
If that didn't fix it?
You probably need a new tach.
​It's a 20 pole tach and nothing else works.

The speedo has a pickup (pitot tube)on the back of the boat.
​If not all the way down it will work somewhat.
It works from water pressure,
There is a tiny hole in the tip of the pitot tube, it can get very tiny bugs or dirt in it and it won't read right.
​Also the tip can break off and you can't tell unless you know what it looks like.
​Google marine pitot tube.

Having a 110d thermo the gauge might not work real well??

 

[Glastron Boater]

That's what that little white plastic piece is on the back, the speedometer. Good to know.

About the RPM, I think I know what you're talking about, but I didn't see a wire labeled for RPM, so I wouldn't know which to look for.

I think I will pull all gauges out and clean all the terminals. Good maintenance thing to do.

As far as the RPMs, can it be a result from it not being the original engine, maybe the original didn't need that 20pole tach?

 

[jerryjerry05]

The wrong tach in there could be the problem.
Yes the original could be anything??
Pics of the gauges?

 

[Glastron Boater]

Does the face tell you anything?

Or does it need to be pulled out and you need the back?

The more it looks like to me though is just that these are the gauges from the original engine, and don't work so well with this force engine.

 

[jerryjerry05]

That face.
​Looks like a Mercury Tach.
That goes for the temp gauge too.
That might be the reason the temp gauge doesn't work too??

​The 20 pole tach can be found. Google, e-bay, my place if I replace with a Johnson??

 

[Glastron Boater]

I don't mind replacing with anything that works.

I'll buy a whole set of gauges if I need to. My boat has speedometer, temp, tach, and fuel. I wouldn't mind a battery gauge also.

I don't mind spending the money, as long as it's going to work with my 87 force motor.

Now you said it looks like mercury gauges, such as mercury/mariner? Not force by mercury marine?

 

[pnwboat]

If the tach is working , but the wrong one (not a 20 pole tach) and it's hooked up correctly, it will work but it won't indicate the correct RPM. If it doesn't work at all, then I would suspect that maybe the tach wire is not hooked up, or like Jerry suggested, loose or corroded wires, or a bad tach. The tach signal comes off of one of the Green/White wires on the rectifier. You can run a temporary wire directly from the rectifier to the tach and see if that works.

Just an FYI.....The temperature gauge looks like it's more for an automotive type closed cooling system motor that normally operates in the 160?F - 180?F, not an outboard. The maximum normal operating temperature for the Force outboards is around 130?F - 140?F. The needle on your temp. gauge won't move very much even under normal running conditions.

 

[Glastron Boater]

I'll look at the wires at the rectifier.

What kind of numbers should I be looking for? Engine running or off?

About the temp gauge, I thought it started kind of high for having a 110 thermostat in it.
This gauge "works" since it jumps when ground directly. I don't know if the sending unit is for a gauge Or just a buzzer though.

 

[pnwboat]

Just realized that I made a mistake on the wire color. The wires on the rectifier you need to look at are Green/Yellow, not Green/White. There should be two Green/Yellow wires (plus a red and a black wire). If you hook the temporary wire to one Green/Yellow wire connections and get nothing with the motor idling, try the other Green/Yellow wire. Ideally, you should be idling at around 900 to 1000 RPM's out of the water with muffs and a garden hose. If you still get nothing from the tach, then I would suspect it is bad, or your not connected to the right terminal on the tach.

Most temp. gauges work off a sending unit that is matched to the gauge. The Force outboards have a overheat temp. switch with a bi-metal element mounted on the head with an orange wire coming off of it. When the head gets too hot, the bi-metal element expands and closes a contact that in turn causes a buzzer mounted under the dash to go off.

If you have a 110? thermostat, then you probably won't see the needle move.

 

[Glastron Boater]

OK. I've been taking to jerryjerry05 through PM on the temp gauge and thought that was the issue... I don't have a buzzer that I know of, just the gauge. It is not the original outboard unit, Boat chassis/body(????) Is an 81 Glastron HPV 165, but it's powered by an 87 Force 125.

What kind of number/data should I be looking for? To diag temp gauge? And RPM Gauge?

I bought the Seloc book from here (Iboats.com) but hadn't had enough time to research this subject yet.

 

[jerryjerry05]

He sent a pic of the gauges in the boat.
Mercury for sure.
​That's probably why it doesn't work??