Tach calibration ??

[MikeP]

Yesterday I decided I would calibrate the oem tachs (Sun tach senders on Glendinning, elec tachs at helms) to get them as "spot on" as I could. But I found that the calibration screw in the back of the tachs had no effect on the reading at all. Moving them full travel in either direction did not change the needle position at idle.

So what's up with that?

 

[rsmith]

I seem to remember doing the same on my whaler tach to no avail. I replaced the mech tachs on the Hatt when I RB the engines so I would start with 0 time tach hours. One reads 100rpm fast. I called SW They basicly said live with it.

 

[Boatnut]

Assuming the tach are analog readouts, you might try adjusting the units at a higher rpm. On analog systems typically there are 2 adjustments, one for offset one for gain. Offset is adjusted at the low end reading, and gain set at the high end reading. Also try calling the OEM for some help. Good luck

 

[Vincentc]

I did a major adjustment on my OEM FB tachs and replaced them with digital Aetna's. At first the new digitals were way off then I changed the dip switches and they matched the hand tach measurement almost exactly.

Comparing the digitals with the helm analogs, I do not know how you could adjust the analogs. At one RPM range they read high and at another low. Since I have a glendinning, tach accuracy is not that pressing and if I really want to know accurate RPM, I just climb up to the FB.

 

[Trojan]

I did a major adjustment on my OEM FB tachs and replaced them with digital Aetna's. At first the new digitals were way off then I changed the dip switches and they matched the hand tach measurement almost exactly.

Comparing the digitals with the helm analogs, I do not know how you could adjust the analogs. At one RPM range they read high and at another low. Since I have a glendinning, tach accuracy is not that pressing and if I really want to know accurate RPM, I just climb up to the FB.

My analogs had a screw inside the cover accessed from the backside.

What did you have to change to convert to the Aetna's and how much did it cost.

BILL

 

[Vincentc]

Bill,
I purchased the Aetna's for a little over $200 each about a year ago. They rode around on the boat for several months before I got around to installing them.
You can use the same connection as the analog tachs. Mine run off of the glendinning sender. I needed to add a 12v positive line for the light and I ran a 14ga wire from the key switch to the tach.
I recall the man I spoke to at Aetna saying, "It's so easy, your wife can do it."
The instructions say you should use shielded wire for the sender wire and I purchased enough for all 4 tachs at an electronics store ($60) or so and ran the wire from the back of the helm tachs to the Aetnas. The Aetna tech support told me afterwards that was not necessary, but it apparently didn't hurt. The original sender wire still runs from the glendinning to the helm analogs.

Mine are LCD and you can see them on the Aetna Engineering web site. They fit in the same cutout, but do not look as good/traditional as the originals, but form follows function.

 

[MikeP]

DId you check the digital tachs against a photo tach? Putting a digital tach in place of an analog tach doesn't directly affect accuracy. The digital tach is just taking the analog signal and turning into a digital display. Unless it's "counting" revolutions using a flywheel magnet, optical reflector, whatever, on the engine, it's no more accurate than what was there before and may be less accurate. Kinda like "digital" tire pressure gauges...just a digital display (which can add another source of error) for the analog signal.

 

[Vincentc]

The Aetna tech expressed reservations regarding the Glendinning sender but suggested I try it before buying a new sender or bypassing the Glendinning.

I did check the new tach against a photo tach where I put a piece of reflective tape on the flywheel. They were closely matched at various rpm ranges.

 

[Trojan]

Bill,
I purchased the Aetna's for a little over $200 each about a year ago. They rode around on the boat for several months before I got around to installing them.
You can use the same connection as the analog tachs. Mine run off of the glendinning sender. I needed to add a 12v positive line for the light and I ran a 14ga wire from the key switch to the tach.
I recall the man I spoke to at Aetna saying, "It's so easy, your wife can do it."
The instructions say you should use shielded wire for the sender wire and I purchased enough for all 4 tachs at an electronics store ($60) or so and ran the wire from the back of the helm tachs to the Aetnas. The Aetna tech support told me afterwards that was not necessary, but it apparently didn't hurt. The original sender wire still runs from the glendinning to the helm analogs.

Mine are LCD and you can see them on the Aetna Engineering web site. They fit in the same cutout, but do not look as good/traditional as the originals, but form follows function.

Thanks Vincentc. My tachometers on the fly bridge change on a daily basis.
Bill

 

[Tim Powell]

Thanks Vincentc. My tachometers on the fly bridge change on a daily basis.
Bill

I READ HAD UNDERSTAND AII THE TROUBLE TACKS HAVE OR ARE HAVING.I have chased this problem for years now but finally nailed it.hrere were the multiple problems
1 cables were worn both inside the housing and to small causing wobble
2 sending units were off and worn inside inside the sending unit were reading incorectely the pens had play in them
3 the glendenning had some play turn off the glendenning the tacks would smooth out some what sent the glendenning to factory and rebuilt it
4 poor conection in the fuse holder in the bilge
5 tacks themselves were old and some coroson inside
6 about 1000 dollars worth of total parts and 3000 worth in worry it is fixed
7 now steady as a wedding organ
8 IMPORTANT do not purchase a t which fits directely on the motor and the sending unit screws to on one side and the cable to the glendenning on the other.There is a pen which is about 2to 3 inches long which fits between the t and the motor. It will sheer off and there goes tack and glendenning guaranteed it will happend at the time you are in a scrape.The pens are in short supply trust me on this one.. Tim

 

[GJH]

Glendinning doesn't make senders. As my old Sun senders attached to the Glendinning failed. I replaced them with Aetna's substitute; they screwed right in. About a 5 minute job including rewire.

 

[Tim Powell]

Glendinning doesn't make senders. As my old Sun senders attached to the Glendinning failed. I replaced them with Aetna's substitute; they screwed right in. About a 5 minute job including rewire.

i agree glendenning does not MAKE senders but they do sell them They also sell the correct cables (the thick ones) the ones that do not wobble causing the sender to read incorrectely. Tim