OMC---tach readings off

[Snickers89]

So, I bought a digital hand held tach to verify my 25 year old analogue tach. Leaving the boat on the trailer I get about 100rpm high at idle and 300rpm high at 3600 RPM.

Can I calibrate?
Is there a digital replacement thats plug and play?
Other options?

[FUJIMO]

which 1 do u think is right?

[FUJIMO]

no, analog cannot be fine-tuned.

[Snickers89]

I think the digital is correct. When I figure in the analogue into the prop slip calulators, I get some pretty high slip readings and I dont think they are correct. I left the boat on the trailer, friend running throttle and I held the tach next to flywheel to test. I really prefer not going WOT down the lake to test any higher RPM.

Would a new analogue tach be more accurate or no guarantees on that?

[FUJIMO]

contact your local omc dealer for up to date digital plug & play tachometer.

[Snickers89]

If they'd ever answer their phone, I could

[Snickers89]

WElp, 4th dealer finally answered. I'm told there's no conversion from a 1996 OMC to current digital BRP guages.
Might try my luck on a new analogue guage and hope for the best unless somebody has a diff idea?

[H2OPERF]

buy one of the tinytachs that you wrap a wire around one of the plug wires, usually has an hr meter too. Have used them for yrs leave it on the ph see rpm while ur testing at the motor.. one in my motor is exact to what the ecu sees..

[flabum1017]

You can try rotating the adjuster in the back of the tach back and forth a couple times (look at what it's set to first and put it back there) Sometimes corrosion will set in on the adjuster contacts.............

[Motv18]

It’s normally the parts that move the needle getting weak. Or the needle slips,

occasionally it’s in whatever feeds the pulse to the tach. I assume it was a clamp on spark plug wire tach reading vs the tach. You can verify the pulse signal by switching to ac hertz to capture ac +- cycles like your house current being 60hz. And doing math. I forgot the math for rpm x magnet/ 60 or something ( like on mercs that tap the charge magnet off the rectifier)

[FUJIMO]

If they'd ever answer their phone, I could

...oops, yeah, you mean cause OMC went out of business 3 days before Christmas back in 2000...? But I guess you mean cause of the Corona Virus shutdown, right?

[Snickers89]

No, I mean my local dealers don't answer their phone. Their service is terrible. BRP aint much better. I've tried calling the mothership a few time for help and they have failed each time.

Tahnk you to those with helpful suggestion. I'll follow through with those.

[FUJIMO]

when you get through to them(BRP), they supposedly can still order parts for motors from before the bankruptcy. supposedly. let us know how you cure your tach issue, like to know what you did to fix this.

[Snickers89]

Update: I rotated the setting switch on the rear of the tach hoping to clean up the internals. No luck
I bought a "tiny tach" and ran the boat. That worked slick. I found the old analogue unit 8-9% off throughout the RPM range. I would run the analogue unit at even readings ie 5000rpm then read the tiny tach. I did this at 2000, 3000, 4000, 5000, 6000, 6600 rpm and wrote down the tiny tach readings. It fluctuated from 8-9% higher on the analogue than the digital tiny tach.
I did buy a new analogue unit but havn't installed it yet.

Thank you scream and fly for the suggestions.