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Rev counter not working

E

eddio

Member
First the good news: My old 1996 Maxum is now running sweetly, pulling me up onto the plane well and 'flying' across the bay. Now to the smaller stuff: The tach has not worked since I bought the boat, and the needle is stuck, showing a constant 1,000 revs. This may just be some internal corrosion, as an electrical malfunction would not keep the needle off the stop all the time. Has anyone dismantled a tacho? Is there a 'correct' way to do it before I mess it up?

Any thoughts and observations would be appreciated before you guys get aboard and escape to go fishing!

Thanks


Eddio
 
The correct way to dismantle is to buy a new one and be done with it..........No repair can be done by you. You have no way to fix or calibrate it. Niether do we.
 
kghost said:
The correct way to dismantle is to buy a new one and be done with it..........No repair can be done by you. You have no way to fix or calibrate it. Niether do we.
Click to expand...

Ditto... I have a strong background in electronics and have dismantled a few electronic tachs "for kicks". While you could dismantle the tach and possibly "fix" the stuck needle, closing up the tach, given its construction, would be problematic. What I call "desert isle fixable", i.e. if you are stranded on a desert isle and need it to work for a few hours or a day so you can get to food, its fixable.
 
Thank you sandkicker. I appreciate your 'fixable' terminology! I suppose if it is gash anyway I may as well have a go! It looks like an expensive bit of kit however, so I may cast around for a chum who, like yourself, knows a little more. A few beers may be in order here.
 
So long as you are going to have a go... problem likely is , as you suspected, purely mechanical. The several tachs I've opened up all open the same way. The tachs are "sealed" by a continuous crimp of the front bezel that contains the "glass" back around the flanged front of the case. To open, take a small stright bladed screwdrive, and pry the bezel away from the flange. You will have to work it about 1/16 of an inch at a time. A pair of small (preferrable bent nose) needle nose pliers will come in handy to straighten the bends enough so the bezel will come off the case. Resealing the case is problematic as you will need some small amount of sealant and something to crimp the bezel back. In production this in done with a large mechanical press with a ring shaped "punch" and a "die" that bends and folds and flattens the end of the bezel around the flangs on the case.
 
Thank you sandkicker. I'll take the tach out in a day or two, when work permits. Today I shall be on the water, skippering a 60' waterbus. No accurate tach needed aboard this old lady with her rumbling diesel engine - just as well, as it varies its reading as we go across Cardiff Bay at a massive 5 knots. Nice work!
 
Diesels require different tach setups given they don't have ignition pulses to count. Did this tach ever work for you?
 
Hi. The diesel engine is on the ninety eight passenger waterbus that I skipper. The non-functioning tach is on my 4.3 Mercruiser (1996) aboard my Maxum. When the tach on the waterbus does not work properly I hit it with the commentary microphone and it works again. Old school :)
 
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