1974 Mercury 850 serial#4123383 / bad stator

[Doc279]

Re: 1974 Mercury 850 serial#4123383 / bad stator

I just checked my Fluke meter - it is a model 87 True RMS multimeter. I will install a new 9 volt battery just in case it is partially dead?
It does not tingle my tongue! LOL

 

[sam am I]

Re: 1974 Mercury 850 serial#4123383 / bad stator

87's are 20Khz bandwidth, still should see that stator's AC....bizarre.

Put the meter on DC, turn the flywheel by hand slowly, watch the analog scale, see any quickie pulses?

Same on AC turning by hand, any pulses?

And can you double check the resistance spec? Looking at mine (not the same but should be close for all intense purposes) it should be lots lower, like "generally less than 1Ω"

Your book says it should be 75Ω? The battery charging circuit winding?

 

[Doc279]

Re: 1974 Mercury 850 serial#4123383 / bad stator

Sam
The new battery in my meter changed everything! Reading between the leads from the stator and disconnected from the rectifier - I am showing 0.2 ohms. I checked the AC output with the meter set on AC and it is showing output. I did the check on AC and DC by turning the flywheel by hand and it does pulse quick random numbers. I found the rectifier test in the manual and it failed! I do not have an extra diode type rectifier but I do have an extra plate style rectifier. Will test that one tomorrow.

I was looking at the wrong chart in the manual - 1975 850 ohm value on the Rx1 scale is .3 THE 1976-77-78 shows .75 ohm value
it is a different stator by part number.

I am almost positive that the stator is good and like someone else said - the rectifier is bad. I hope to start this motor tomorrow - we have having a heat wave and will see almost 50 degrees. THANKS YOU so much for your thoughts and input!!!!!

Happy New Year All! Posting at 3:30 AM - obviously I could not sleep LOL

 

[Doc279]

Re: 1974 Mercury 850 serial#4123383 / bad stator

Browsing around in a used book store yesterday I found a Mercury outboard service manual C-90-75512 that covers years 1975 - 1978
Models covered starts with a Merc 45 and goes through to a Merc 1750 $10.00 SCORE!!!!!!!!

 

[sam am I]

Re: 1974 Mercury 850 serial#4123383 / bad stator

ahhhhhhhh, cool.

Still should be able to see AC while cranking though, pretty standard test. The random pulses are a good sign(some loops are good at least) BUT your cranking for AC verifies things a bit more for example that all the winding's are there and not some/most shorting to one another(give you pulses but low or no AC/DC). You should be able to see something around like 10-20VAC cranking if i recall right, won't be surprised if you have a shorted stator too with those no AC's to speak of. GL

 

[Doc279]

Re: 1974 Mercury 850 serial#4123383 / bad stator

I finally got the motor running this morning and it sounds great. It took a few tries to get it started but once warm it ran very well.
I changed the rectifier to a plate style that I already had. With the motor running I am seeing 8 volts off of the rectifier wire. I imagine that it would increase with added rpm. On the hose and on my stand - I did not get it over 2000 rpm or so.

I am pleased and will mount this motor on my pontoon boat in the next few weeks. Kinda cold and I want to spray paint the motor before mounting it. I found the part number for the radio shack 25 amp 50 volt rectifier - it is part # 276-1185 and it sells for $4.50 I will pick one of these up in the next little bit for this motor.

Thanks all for the help!

 

[sam am I]

Re: 1974 Mercury 850 serial#4123383 / bad stator

Go Doc go........Get that 8 volts up to 13/14 and you're GOLD'n

 

[Doc279]

Re: 1974 Mercury 850 serial#4123383 / bad stator

I got my 850 mounted on the pontoon boat last week and connected the shift cables and wiring harness. I took it to the lake this morning and it fired up quickly and ran very well. I've got a good steady stream of water from the tell-tale. It started to snow and the wind picked up so I could not run it very long but I am pleased thus far. Checked the voltage at the solenoid while the engine was running and I saw 13.2 volts. Thanks for the help everybody - come on warm weather!!!!