Tachometer started reading high

[jgwufgator]

Make: Johnson
Model: J200VXSS"S"
Serial: G04806863
Year: 2000

On the last trip out, my tachometer was reading way high (~1000-2000 RPMs too high). What would cause this?

Thanks.

[Bassmeister]

Could be reg/rectifier, Do you have wingnuts on the cranking battery? If so replace with ss nuts and locking washers,as the wingnuts can work loose and cause voltage spikes that in turn cause a host of problems. On top between the heads is the pp,under there is the reg/ret.....look for melted potting or burnt wires.

[jgwufgator]

I've got lock-nuts on the battery, so I don't think that is the problem. Do I have to remove the powerpack to see those wires? In a related note, my voltmeter on the dash shows high voltage, but if I actually check the voltage with a multimeter, it is normal.

Thanks for your reply.

[jgwufgator]

So I pulled the power pack off and see no burnt wires. Do bad tachs ever read high? I found a butt-connector disconnected under the power pack, but I don't know if I pulled it when I pulled the power pack up, but I don't think I did. It was orange with a black(?) stripe.
My dash voltmeter also reads high, but I put a multimeter on the battery and the idle charge voltage is 14.48V, while the dash voltmeter says about 16.5V.

[ChampioNman]

14.48 V is somewhat high at idle that would be the upper end at WOT idle charge should be around 12.8-13.4 V.


Part numbers are as follows:

BRP 586271
CDI 1934641

Sierra 18-5831

All around the $275.00 price range.

[jgwufgator]

So what am I looking at here? Could it be that the engine isn't under load (idling on the hose) which allows it to rev higher which in turn leads to higher output voltage?

Edit: I'm getting my posts crossed up... Definitely recifier/regulator???

[ChampioNman]

Idle is idle you may have a 300 rpm difference out of the H20 on muffs. you should be in the 12.8-13.4 range. At idle.

[jgwufgator]

Thanks for your help. What causes them to go bad? Overheating? Is this a water-cooled regulator? From the service manual, it looks like it is.

[ChampioNman]

Yes it is water cooled, who knows why they go bad, why does a light bulb pop? It's just its time.

[jgwufgator]

The only reason I ask is so I can correct the possible cause. Thanks.

[ChampioNman]

When was the last time you changed the H20 pump?

[jgwufgator]

Not for a couple of years, but the water pressure gauge indicates about 25 lbs pressure at full throttle.

[jgwufgator]

Well, I just pulled the rectifier/regulator. I don't see any obvious issues (not that I'd expect to), and the service manual doesn't say how to test it (while removed), so I'll order a new one (or pick one up, if they have it) tomorrow.

I hope this fixes it.

Thanks!

[jgwufgator]

Stupid question:
The regulator/rectifier on the schematic at BRP's site looks totally different (heat sink fins verses the eight cylindrical cooling posts mine has). Mine has the same part number printed on the unit, so I'll assume it is A-OK. Could this just be a newer, better unit?


Modified by jgwufgator at 3:25 PM 9/1/2008

[1FASTLASER]

Gator mine looked different when I got it. It is the same animal according to my tech. I just havent had time to install mine as of yet.

[ProcraftMike]

I had the same issue this past weekend. My tach was saying I was around 7k at full throttle and 1200 RPM at idle, which I know wasn't the case. My Teleflex tach has a dial on the back, where you can swittch the poles from 2 pole, 4 pole, 6 pole or 8 pole (I believe those are correct). I simply crawled underneath and turned the dial back and forth a bit, then settled it back to 6 again. My tach started reading fine after that.

I'm not sure if you have the same set-up or not, but it might be worth a look.

[jgwufgator]

So I got the new reg/rectifier today. Same part number (586271). The one that came off my motor has two wires with bullet connectors (purple and grey) and a large two pole connector with yellow wires. The new one does not have the purple wire. Is that the keyed power wire?

Why? I'm confused.

Edit: I can't see a use for the ignition wire on the regulator in the first place.

Second edit: OK, I called BRP. They told me the purple wire was no longer necessary. Thanks for everyone's input.


Modified by jgwufgator at 8:27 AM 9/5/2008


Modified by jgwufgator at 10:08 AM 9/5/2008

[jgwufgator]

Championman,
I installed the new rectifier/regulator. Idle voltage is now ~14.1, so it is lower, but not what you think it should be. But, the tach still was reading 3000 at idle. I pulled the dash plate off and moved the pulse/cylinder selection screw to 4C back to 6C. Idle RPMs now ~1000. Getting all of those wires to fit under the power pack was a NIGHTMARE.

Anyway, thanks for your help.