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Author Topic:   Johnson 70-HP: Tachometer, Electrical Problems
dangerdan posted 07-20-2006 09:27 AM ET (US)   Profile for dangerdan   Send Email to dangerdan  
[The author provided a narrative of the sequence of electrical problems he has been experiencing on his 1989 70-HP Johnson; he is apparently soliciting advice on how to proceed in making repairs.--jimh.]

--[tachometer] stopped working

--weeks later dead battery and no charging; told to change regulator

--rectifer changed; it still not working

--now trim-tilt will not work

--tilt up hear a buzzing coming from top 40-ampere fuse

--tilt down clicking heard in lower 40 amp

Whaler_bob posted 07-20-2006 01:51 PM ET (US)     Profile for Whaler_bob    
The other part of the charging circuit is the stator under the flywheel. It's possible one of its leads are broken, frayed. or corroded, and/or the charging coil in the stator has gone bad. You need to troubleshoot it. That buzzing you hear when you try the trim is from the trim and tilt motor up/down relays. They don't have enough voltage to hold the spring arm's down due to the battery low charge state and it results in a oscillating condition- that's normal and will stop with proper operating voltage. Also, check your battery for water. It won't charge if it's dry.
jimh posted 07-20-2006 07:47 PM ET (US)     Profile for jimh  Send Email to jimh     
When working on any battery-operated electrical device, the first component to check and verify is the battery itself. Verify the battery has a full charge and does not have any shorted cells or other problems.

The charging circuit of a traditional outboard motor is well described in the REFERENCE article

Permanent Magnet Alternators

Lack of indication on a tachometer is often a symptom of other problems, not of a failure of the tachometer. Based on your narrative of the problems and the sequence in which you observed them, my guess would be that:

--the rectifier failed
--this caused the tachometer to stop working
--the battery was not being charged so it was drained
--this caused other problems like not enough power to run the trim motor

Test and check all the elements of the battery charging circuit:


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