Help diagnosing rectifier/stator problems

[mcgreavster]

I have a 1988 XP150 I bought late last year and the tach has never worked. I did some reading online and saw that it could be a bad rectifier so I jumped the tach from the rectifier directly to the stator and it started working. So does that definitely mean my rectifier is bad? I did a rectifier resistance test and the results were-

Red ---> Yellow / Black ---> Ground = 2.46M Ohms
Red ---> Ground / Black ---> Yellow = 27.2M Ohms and it seems like it just kept going up

Red ---> Yellow Gray / Black ---> Ground = 2.46M Ohms
Red ---> Ground / Black ---> Yellow Gray = 27.2M Ohms and it seemed to also continue going up

My manual says it should be infinite in one direction and zero in the other. Does the fact that the meter seemed to continue to increase count as "infinite" and is 2.46M Ohm low enough to be considered "Zero"? My guess would be no, but it also says "if the reading is the same in both directions the rectifier is defective", which my readings were not.

Now I also did a Stator resistance test because I've read a bad rectifier can destroy a stator and vice versa and the results were-

Red ---> Yellow / Black ---> Ground = 0 Ohms
Red ---> Yellow Gray / Black ---> Ground = 0 Ohms

Red ---> Yellow / Black ---> Yellow Gray = .3 Ohms (sometimes jumping up to .5 Ohms)

So this means my stator is shorted to ground since I'm not getting infinity? Also worth mentioning my stator looks to have a lot of black substance around the coils, so it's probably melted?

If anyone can help me sort through this info and try to help me figure out what I need to replace or what other tests I need to do that would be awesome because I'm really over my head with this stuff, thanks!

 

[Chris1956]

The easiest test of a rectifier is to check the voltage at the battery with the motor off, and then start the motor and rev it a bit. If the voltage goes up, the rectifier is likely good.

Since your tach operated when connected directly to the stator, the stator and tach are good. So the bad candidates are the rectifier and the wiring. If the wiring is shorted, the boat may not charge and the tach may not work.

 

[mcgreavster]

The easiest test of a rectifier is to check the voltage at the battery with the motor off, and then start the motor and rev it a bit. If the voltage goes up, the rectifier is likely good.

Since your tach operated when connected directly to the stator, the stator and tach are good. So the bad candidates are the rectifier and the wiring. If the wiring is shorted, the boat may not charge and the tach may not work.

I checked voltage at the battery and I had 12.7V to start. 12.5V while it was running and 12.6V after. So the 12.5V means it's running off the battery? I just ran it on muffs so I didn't run it WOT or anything.

 

[flyingscott]

The charging system on your motor is separate from the ignition system so your motor is not running off of the battery. Don't hook the tach right to the stator anymore it's not good for it. A sign the rectifier is out is the tach not working I would replace your rectifier. If your stator is dripping it is time for replacement.

 

[mcgreavster]

The charging system on your motor is separate from the ignition system so your motor is not running off of the battery. Don't hook the tach right to the stator anymore it's not good for it. A sign the rectifier is out is the tach not working I would replace your rectifier. If your stator is dripping it is time for replacement.

Only ran the tach connected directly to the stator for 30 seconds to see if it was the tach or the rectifier. Is there any other tests for the stator besides a resistance test? If the stator still works but just looks overheated I'd rather not spend $350 unless it's not working.

 

[oldboat1]

That motor has a water-cooled rectifier/regulator, doesn't it? If so, you might want to go ahead and replace it. Along with affecting tach and charging functions, I think a failed regulator/rectifier could be a fire hazard.

 

[mcgreavster]

That motor has a water-cooled rectifier/regulator, doesn't it? If so, you might want to go ahead and replace it. Along with affecting tach and charging functions, I think a failed regulator/rectifier could be a fire hazard.

Yes it's water cooled and I already purchased a new one, just need to pull the flywheel before I install. Just wondering about this stator now. I don't really know the tests to do to tell me if its okay or not.

 

[Faztbullet]

If stator open windings look discolored or encapsulated coils are weeping black ooze you need to replace. You need to check and see if rectifier has 12V on the purple wire when key is on as this turns rectifier on/off. If it has voltage the rect/reg is bad. The newer ones do not have this feature so tape the purple wire bad as not used. Replace the impeller as the block not filling from weak impellers are most cause of water cooled rect/reg failure. Make sure "P" hose goes up over top of head and then back down to outlet.

 

[David Young]

I checked voltage at the battery and I had 12.7V to start. 12.5V while it was running and 12.6V after. So the 12.5V means it's running off the battery? I just ran it on muffs so I didn't run it WOT or anything.

​That's how I knew my rectifier was bad. Battery with the motor off was around 12.5 volts, battery with the motor running was 12.7 volts. Changed the rectifier, volts with the motor running would go up to 15 , almost 16 volts. Tach started working right too

 

[Fed]

Disconnect the stator wires from the terminal block then measure the resistance between them & the resistance to ground.
The 9 Amp stator should measure 0.7 Ohms between the wires & infinity or a very high reading to ground.
The 35 Amp stator should read 0.17 Ohms between wires.
Got a model number?
Check the meter goes to zero when you short its leads together, if not then adjust to zero or allow for the error in your readings.