No tach,no charging

[Ifishmuskie2]

1994 mariner 115hp on StarCraft.
Boat worked fine then next trip no tachometer and no battery charging.
I pulled the rectifier and it has a burn spot in the clear underside.
So I put a new rectifier in and water tested.
Still no tach or charging.
What do I do now?

 

[Mc Tool]

I would say at a guess that you have also got a fried alternator , For the reg to have a hole burnt in it something has got very hot , usually a short in the reg and that will cause high current flow in the alt windings and fry them too . you need to disconnect the 3 wires from the alt and measure the resistance between them, and to earth . Winding resistance should be between 0.2 - 1 ohms ....not a dead short or open circuit ( with such low resistances you need to touch your meter probes together to see what the resistance reading is and then factor that in when you test the windings ) . Resistance between windings and earth should be totally open circuit.

 

[Ifishmuskie2]

I’m going to check it right now.
I have people wanting to go fishing.

 

[Ifishmuskie2]

I can’t see any access to the stator wires.

 

[Ifishmuskie2]

I disconnected the red, red and white, blue, blue and white.wires. They are open circuit to ground.

 

[Mc Tool]

there should be 3 yellow wires .... these are the 3 phases from the alt and should go to the reg / rect you replaced . resistance should be between 0.1 ohm and 1 ohm between any two yellows ( check them all ) and open circuit between any yellow to ground .

 

[Ifishmuskie2]

Ok thanks. I see the three yellow wires.
I had to stop for dinner. I’ll be back at it first thing in the morning.

 

[Dukedog]

bad stator.......... maybe regulator also.. it sounds like ya don't have tha right stuff ta check all three pieces so.......... replace all three pieces, regulator, rectifier, stator and be done with it.............

 

[Chris1956]

According to Crowley, lower serial numbers of that motor have a unregulated charging system consisting of a stator and rectifier. Higher serial numbers have a stator and voltage rectifier.

Stators are usually tough enough to easily survive rectifier burning. Usually there are 2 yellow wires of the stator that connect to the two AC terminals on the rectifier. Most OEM rectifiers are grounded to the block. You might check your connections and if correct, test the new rectifier.

The tach signal wire is connected to either of the yellow wires on the rectifier.

 

[Ifishmuskie2]

(1994?)
Mariner 115hp. 0D298748
Rectifier has two yellow, two red, one grey
And a ground to the mounting bolt.

 

[Ifishmuskie2]

This is the old rectifier.

 

[Ifishmuskie2]

On old rectifier one yellow and one red have closed circuit.
On new rectifier two yellows and one red have closed circuit.

 

[Ifishmuskie2]

The two yellow wires are open to ground.
They are 002 to each other.

 

[Ifishmuskie2]

Two big yellow wires.

 

[Texasmark]

From my memory: Yellow is AC input from Stator. Grey is tach output to tach gauge. Small red is operating power and large red is battery charging power output.

 

[Ifishmuskie2]

I guess next step is to run on muffs and check voltage in red wires from stator.

 

[Chris1956]

This is the old rectifier.

View attachment 419614

That is a voltage regulator. Likely a 20A version. Replace with the same.


This is a rectifier. It is simply a bridge of 4 diodes. The connections are 2 AC terminals that go to yellow. The grey tach signal wire also connects to one of the AC terminals. The + terminal gets the red wire and the - GC terminal gets grounded to the frame.

 

[Chris1956]

You can get replacement VRs both OEM and aftermarket. I think I installed the Sierra or CDI brand. They work just fine.

 

[Ifishmuskie2]

I already installed a new one and it didn’t change anything.
I just ran the engine on muffs and the voltage on the yellow wires was12.3. So just the battery voltage.
Now what? Replace the stator?

 

[Chris1956]

Check for a fuse in the charging circuit. I don't expect one, but some Mercs had 'em in the wiring connectors.
Make sure the tach is not shorted to ground. Then Ohm out the stator across the two yellow wires. Stator should be .18 - .45 ohms, so not a dead short.