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Old 03-20-2017, 12:47 PM   #1
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Possible Bad Tachometer

My older Yanmar 3 cylinder engine has a tach sender on the bell housing. My Yanmar tachometer isn't working. I have tested the sender and the wires to the tach and it all checks out. Over the weekend i started the engine for the first time in 8 years or so and it runs great. If the tachometer is bad do I have to replace it with a OEM Yanmar tach or can I buy another brand?
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Old 03-20-2017, 01:56 PM   #2
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Check that with engine running you get a few volts of AC from the sensor with tach disconnected. I have had good luck with VDO vision series universal tachs. Programmable for whatever AC source. Hour meters suck, though.
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Old 03-23-2017, 11:00 AM   #3
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Hour meters suck, though.
Ski, can you elaborate? I am about to do an entire panel refit with VDO gauges. Just curious.
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Old 03-23-2017, 11:16 AM   #4
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Ski, can you elaborate? I am about to do an entire panel refit with VDO gauges. Just curious.


John,

I'm in the process of the same upgrade using the latest VDO gauges, but at the advice of several professionals I am using Aetna digital tachometer's instead of VDO. Check them out or PM me and I'll tell you what I found out about them.
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Old 03-23-2017, 11:24 AM   #5
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Greetings,
Mr. LM. Any problem sharing the opinions regarding VDO's? At some point I will be replacing the two Motorola tachs due to one dead hour meter so any information would be a help to me. I do have easy access to Lauderdale Speedometer occasionally and it seems they stock a wide variety of instruments that might be a viable replacement. Thanks.
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Old 03-24-2017, 10:05 AM   #6
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Greetings,
Mr. LM. Any problem sharing the opinions regarding VDO's? At some point I will be replacing the two Motorola tachs due to one dead hour meter so any information would be a help to me. I do have easy access to Lauderdale Speedometer occasionally and it seems they stock a wide variety of instruments that might be a viable replacement. Thanks.
I recently had a VDO Viewline Onyx tach fail. During a sea trial test of WOT, it seemed fine until 2000 rpm where it just stopped. A digital tach showed that engine was turning 2975 rpm. I tried calling VDO support three times and left messages twice. Never got through or heard back from them. I cleaned and adjusted the sensor, but no joy. I swapped out the tachs and determined it was defective. Just to be on the safe side, I replaced the sensor too, but no change. The VDO specs show these have a tolerance of plus/minus 2.5% or 75 rpm on a 3000 rpm engine. My local Cummins professionals and a number of captains of larger luxury yachts and sportfish boats all recommended Aetna Engineering digital tachs as being the most reliable and accurate you can buy. A bit more research on other boating forums, and again, Aetna seemed to be best-in-class when it came to marine tachometers.

I bought a pair directly from Aetna and am completely satisfied. Beautifully constructed of metal with advertised accuracy of plus/minus 1 rpm! Tech support was reached easily and very helpful. No more guesswork when it comes to synchronizing or knowing what your engines are actually turning. When checked with a digital handheld tach they were spot on.

I am still using VDO ViewLine Onyx instruments for the rest of the upgrade because I like them and think they are generally high quality, even though their tech support so far has been miserable. YMMV

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Old 03-24-2017, 11:11 AM   #7
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Greetings,
Mr. LM. Thanks. Poor after market support, tech or otherwise is a valid reason for avoiding future potential headaches.
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Old 03-24-2017, 11:32 AM   #8
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Greetings,
Mr. LM. Thanks. Poor after market support, tech or otherwise is a valid reason for avoiding future potential headaches.
Wow, what a difference a day makes. As I mentioned, I am still upgrading my panel with VDO instruments. The synchronizer is not functioning as expected, so I tried Lauderdale Speedometer who referred me to Jared Hall at VDO in the tech support department. Well, I got through this time and as it turns out, Jared answered the phone. He was one of the most helpful support specialists I have ever encountered! He knew exactly what I was facing and asked me to send the instrument directly to VDO to his attention to be checked out. He apologized for my prior support experience and said there were only two of them and they were sometimes very busy.

So, at this point I have no reservations in using VDO gauges, but I still prefer the Aetna tachometers.
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Old 03-24-2017, 11:44 AM   #9
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Greetings,
Mr. LM. I shall erase the bad VDO vibes from my memory banks...in 3...2...1...Ooohhh something shiny.

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Old 03-24-2017, 05:18 PM   #10
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I am planning to replace antiques using VDO also....well maybe Faria as I can get a deal....and already partially into it.

But found VDO online literature and tech support just fine.....needed it to verify Faria requirements.

Did buy old VDO lighting bulbs that were hard to find through a third party....so there is aftermarket support.
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Old 03-24-2017, 05:46 PM   #11
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Greetings,
Along the same lines...If anyone has an old Motorola they're not using AND the hour meter works I would be interested in it please. Tach needn't work, just the hour meter. I suspect one of the internal drive gears is shot in my unit and they are made from unobtanium. Thanks
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Old 03-24-2017, 05:54 PM   #12
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Greetings,
Along the same lines...If anyone has an old Motorola they're not using AND the hour meter works I would be interested in it please. Tach needn't work, just the hour meter. I suspect one of the internal drive gears is shot in my unit and they are made from unobtanium. Thanks
I thought people were still getting parts from Lauderdale Tach...not positive of the name.

Not for your kind of mechanical hour meter in the tach RT?
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Old 03-24-2017, 06:05 PM   #13
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Greetings,
Mr. ps. Well, the last time I was in to Lauderdale Speedometer they told me parts for Motorola tachs were not available. I'm pretty sure IF the parts were available they would have offered to rebuild mine for me. I've also done some web searching and...no joy in Mudville. I strongly suspect my tach IS mechanical and one of the gears/cogs is Kaput. I haven't asked but IF I were able to get parts, I would get LS to rebuild which I'm sure they would happily do ($$).

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Old 03-24-2017, 06:29 PM   #14
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Must be a different tach that some have rebuilt...

Sorry.....
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Old 03-25-2017, 02:01 AM   #15
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Possible Bad Tachometer

Interesting conversation considering the conversations I had today. I have VDO tachs in both pilot house and flybridge areas so total 4 tachs. All four went out at once! On the starboard side when I crank the engine the tachs read 800rpm for about ten seconds and then die. I can repeat this procedure multiple times and always have the same result. On the port engine when I crank, no reading at all.
Talked to both electronic tech and alternator tech. End result, am pulling alternators and tachs and sending them to the shop on Monday. Cat 3208T/A engines.
I do have Glendinning synchronizers but have ruled them out as the tach pickups are on the alternator and not the synchronizer. They are 12v system and I am getting 12v at the supply the the tach head. Tech on the phone said it is normally half voltage so should be 6v.
Anybody seen a problem like this?
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Old 03-28-2017, 02:55 PM   #16
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I am just catching back up to this topic.. I would only do digital tachs if I still had analog to go with it. I imagine I would get used to it but I prefer the sweep of the needle. I have also been directed to another brand of gauges that are recommended by Seaboard as well as the local guys here in Houston(Instrument Exchange)....Isspro I think is the name of the gauges. I may go with them.
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Old 03-28-2017, 06:06 PM   #17
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I am just catching back up to this topic.. I would only do digital tachs if I still had analog to go with it. I imagine I would get used to it but I prefer the sweep of the needle. I have also been directed to another brand of gauges that are recommended by Seaboard as well as the local guys here in Houston(Instrument Exchange)....Isspro I think is the name of the gauges. I may go with them.
John,

Isspro are great gauges. Usually, I prefer needles too, but with the Cummins B's a few rpm actually can make a difference at the top. I wanted digital accuracy, but I also wanted the installation to be easily to sync. I did some research and a VDO engine synchronizer will work with the Aetna tachometers, so I'm mounting one of these between them. This matches the rest of the new VDO gauges and will make sync obvious at a glance. The red indicator light goes out when in sync.

Another advantage of the VDO marine gauges is the sealed double pane instrument glass. It does not fog like some others.

Lots of good options out there.

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Old 03-29-2017, 05:33 PM   #18
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Yep...my boat is underpropped and I do keep track of tach accuracy with phototachs so that "few RPMs at the top" are not an issue. I will also be installing boost and pyro gauges to really know what is going on. There is no better way to know how your engines are loading up than to look at EGTs.
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