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Old 11 March 2012, 19:37   #1
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Mercury/Mariner Tacho Rev Counter dead?

I went and got the Mercury workshop manual for the 2002 90HP 3 cylinder 2 stroke and it has nothing on Diagnostics for the Analog guages. So if anyone could tell me what the resistance/voltage readings or inputs to the tacho should be I'd be grateful as my mates analog rev counter appears to be dead.

I'd rather check it and the engine wiring to find out what exactly's wrong rather than simply tell a friend to go buy a new guage and hope that'll sort it!
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Old 11 March 2012, 20:22   #2
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Quote:
Originally Posted by Daibheid View Post
I went and got the Mercury workshop manual for the 2002 90HP 3 cylinder 2 stroke and it has nothing on Diagnostics for the Analog guages. So if anyone could tell me what the resistance/voltage readings or inputs to the tacho should be I'd be grateful as my mates analog rev counter appears to be dead.

I'd rather check it and the engine wiring to find out what exactly's wrong rather than simply tell a friend to go buy a new guage and hope that'll sort it!
Is it the Teleflex or Ultraflex unit (they are the same)?
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Old 12 March 2012, 09:06   #3
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Originally Posted by Nos4r2 View Post
Is it the Teleflex or Ultraflex unit (they are the same)?
Not sure Nos - I don't have it anywhere near me but from memory it looks like this one
http://www.gulfstreamshop.com/Images...s/150/2901.jpg
if that makes it any clearer.
The engine wiring diagram shows a gray wire is the sense wire so it'd be good to know what that should show ignition on and then engine running just in case it's a rectifier or charging issue. Apparently the battery doesn't go flat but I have to qualify that with it never went flat when the rev counter was known to be working before the boat went into hibernation and I only ran it briefly on muffs.
TIA for any suggestions
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Old 12 March 2012, 12:23   #4
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Tacho inputs are usually +, -(or 0V) & Signal.

meter on DCV - Ign off = 0V or thereabouts, on = 12-ish. (Once the engone is running, the usual array of charging voltages should be seen.)

then put meter to ACV, engine off = 0V, engine on will give a variable reading which will bear absolutely no relation to anything of use, but will, if it changes as you rev up & down, at least prove your alternator is throwing something out. (I say no relation as some DVMs get confused a bit if you show them AC that isn't 50Hz).
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Old 12 March 2012, 13:20   #5
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purple =ign live
black= earth
grey =tacho signal from rect/regulater
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Old 12 March 2012, 13:48   #6
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(I say no relation as some DVMs get confused a bit if you show them AC that isn't 50Hz).
And sinewave.

jky
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Old 12 March 2012, 15:06   #7
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It's the teleflex/ultraflex unit if it looks like that.

From memory if you give it a + and - straight from the battery, the needle should move to 0 rpm. If it doesn't, it's gubbed. No point in stripping it, just replace.
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Old 13 March 2012, 08:14   #8
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Thanks 9D280, uncle al, jyasaki and Nos that's all good solid info.
It's all pointing toward my initial conclusion that to use Nos's technical term it's gubbed. Purple black and grey were all wired correctly I metered it DC at 0 ignition off and about 11V ignition on. The fact the needle doesn't budge at ignition on had me thinking it's dead. I should of course have metered it running and as has been pointed out for AC but it's in Winter storage -the kind that has the windscreen off and A-frame unbolted and laid on the console to get it in a shed plus kayaks, grannies, etc stashed in it so getting it out to run it on muffs is a problem hence the enthusiasm for a diag check on the guage itself.

I'll get it run and checked when it comes out of the shed and meanwhile issue the "start saving for a new meter" caution in suitably sympathetic tones. I'll report back when/if I get it sorted.
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Old 13 March 2012, 08:39   #9
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Useful one stop shop detail here on debugging various types of tachometers /rev counter

Troubleshooting Teleflex Tachometer Gauges
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Old 13 March 2012, 10:19   #10
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Other option - do you know anyone with an engine that is near water? Probably easier to tremove the gauge, test it on another boat, and if it is gubbed, you don't need to take it out the console twice!
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