1987 Johnson 150GT, How to Repair Rectifier

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spanky0077

Cadet
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Jul 13, 2011
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Hello I have been reading posts about 1987 Johnson 150GT not charging the battery and it can be the rectifier. My question is, does any one know the step to actually completing the repair once removed or what it is I should be looking for because they are big bucks!!!!!! Also I read that if rectifier is not working my TACH will not work to show me my RPM'S some one please help me. :facepalm:
 
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wilde1j

Vice Admiral
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Apr 15, 2002
Messages
5,964
Re: 1987 Johnson 150GT, How to Repair Rectifier

A failed rectifier/regulator is replaced, not repaired unless you have really unusual talents and way too much time on your hands. It would be easier to build a rectifier/regulator than repair a sealed one, and still not worth the time and effort. BTW, how do you know for sure the rectifier/regulator has failed? A failed stator will also lead to no charging.
 
Barnacle_Bill

Barnacle_Bill

Admiral
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Feb 8, 2004
Messages
6,469
Re: 1987 Johnson 150GT, How to Repair Rectifier

Also a rectifier can be bad and the tach still work. It depends on which diode is blown and whether it shorts or opens.
 
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emdsapmgr

Supreme Mariner
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Dec 9, 2005
Messages
11,551
Re: 1987 Johnson 150GT, How to Repair Rectifier

Your engine has the huge 35 amp alternator. With that setup comes a combination regulator/rectifier. It will manage recharging your battery and will send the signal to the tach for proper operation. After running for a while, your volt meter should indicate a charge rate of around 13.5 volts. If it's reading 12.5 (normal battery voltage) then it is probably not working. An erratic or non-functioning tach is another telltale omen of a problem with the rect/reg. With the amperage that system puts out, the only rect/reg service work I'd be contemplating is a complete component replacement.
 
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spanky0077

Cadet
Joined
Jul 13, 2011
Messages
7
Re: 1987 Johnson 150GT, How to Repair Rectifier

Thank you so much for all your guys help. All the wires seem to be a little melted coming off the rectifier. The previous owners son hooked up the battery backwards. I'm going to order the new rectifier and start there since it is a a little cheaper then the stator.

Any other Ideas?
 
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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 1987 Johnson 150GT, How to Repair Rectifier

Those high capacity combination rectifier/regulators are sensitive. Two things fry them, hooking them up backwards and running them high rpm's with the battery cables loose on the batter terminals. They will generate enough heat to cause an electrical fire..lots of smoke, but usually of little consequence.
 
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