87 25hp evinrude alternator

cadet917

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i have a 25hp electric start evinrude that stopped starting on me. The starter motor pops up but just doesnt have enough juice to turn the motor over. Im only getting 12.07 volts on the battery when the motor is running. Anyone know where the alternator is on these motors or how to test it?
 

F_R

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Re: 87 25hp evinrude alternator

i have a 25hp electric start evinrude that stopped starting on me. The starter motor pops up but just doesnt have enough juice to turn the motor over. Im only getting 12.07 volts on the battery when the motor is running. Anyone know where the alternator is on these motors or how to test it?

The stator is under the flywheel. The rectifier is external. It is all connected to the black screw-terminal strip.

To test, disconnect all wires from the terminal strip. Then check for continuity between any two of the three wires going to the stator. Should show continuity. Then check for continuity between any one of them and ground. Should be no continuity.

The rectifier has six diodes inside. Each diode should show continuity in one direction only. That means twelve tests for continuity on the rectifier. They are: Between a yellow lead and ground. Repeat for the other yellow leads. Then between a yellow lead and the red lead. Repeat for the other yellow leads.

The final test makes sure it is all connected to the battery. Check voltage on the red lead that connects to the rectifier's red lead, and ground. Should show battery voltage.

Before putting it back into service, remove, and clean battery connections shiny bright, and inspect battery cables. A poor or corroded connection is probably what blew the rectifier in the first place and will blow another one if not corrected. OR, connecting the battery backwards will blow it instantaneously.
 

cadet917

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Re: 87 25hp evinrude alternator

ok i will check all that. I am getting a reading of 12.16v on the battery terminals but when i check each cell (its an open cell battery) 1 of the cells has nothing. Is it possible that the battery isn't taking enough charge?
 

cadet917

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Re: 87 25hp evinrude alternator

ok there are 3 wires from the stator and 3 from the rectifier. They are yellow, yellow/blue, yellow/silver.

stator--
yb-y=no cond.
yb-ys=no cond.
y-ys= no cond.
yb-g=no cond.
y-g= no cond.
ys-g=no cond.

Rectifier--
yb-g= cond.
y-g= cond.
ys-g= cond.
yb-red= cond.
y-red= cond.
ys-red= cond.

the red to ground lead shows the battery voltage 12.16v
 

F_R

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Re: 87 25hp evinrude alternator

ok i will check all that. I am getting a reading of 12.16v on the battery terminals but when i check each cell (its an open cell battery) 1 of the cells has nothing. Is it possible that the battery isn't taking enough charge?

Very possible. You have a dead cell. Take it to a battery store for a verification test.
 

F_R

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Re: 87 25hp evinrude alternator

ok there are 3 wires from the stator and 3 from the rectifier. They are yellow, yellow/blue, yellow/silver.

stator--
yb-y=no cond.
yb-ys=no cond.
y-ys= no cond.
yb-g=no cond.
y-g= no cond.
ys-g=no cond.

Rectifier--
yb-g= cond.
y-g= cond.
ys-g= cond.
yb-red= cond.
y-red= cond.
ys-red= cond.

the red to ground lead shows the battery voltage 12.16v

If I am reading your test results correctly, you have an open stator. The first 3 tests should show somewhere around an ohm or so of resistance, not open.

You still have 6 more tests to do on the rectifier. Repeat everything you just did, only with the tester leads reversed. Taking one section as an example, (YB), connect the meter leads between yb and ground. Should show either a high or low resistance. Now, do the same test with the meter leads reversed. If it was high the first time, now it should be low. And vice-verse.

Repeat the entire sequence on all of the remaining leads. 12 tests in all. It must pass all 12 to be good.
 

wilde1j

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Re: 87 25hp evinrude alternator

Also, 12.16 vdc shows a very discharged battery. Fully charged should be 12.7 vdc. When charging system is working, motor at fast idle should give ~ 13.5 vdc across battery terminals.
 

cadet917

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Re: 87 25hp evinrude alternator

with the meter set on 20 VDC i get nothing between the wires from the stator. the tests on the wires from the rectifier give me a reading and when i swap the terminals i get the same number but it will be negative eg.11 vs. -11.
 

cadet917

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Re: 87 25hp evinrude alternator

if the stator was open would the motor even run? The motor does run fine but i have to jump it to start it.
 

F_R

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Re: 87 25hp evinrude alternator

with the meter set on 20 VDC i get nothing between the wires from the stator. the tests on the wires from the rectifier give me a reading and when i swap the terminals i get the same number but it will be negative eg.11 vs. -11.

OK, now you are starting to confuse the issue. The stator test should be done on a low resistance scale (ohms), not a voltage. With the motor stopped.

Same thing on the diodes, use about a 10K-ohm resistance scale.

I should have mentioned up front that many digital multimeters are unsuitable for testing diodes, unless they have a diode test function. A case where old school is better than the high tech. An el-cheapo analog meter works just fine for this. If you are using a digital and get funky readings, get a different tester. Even the old-fashioned battery-and-a-light-bulb tester will do.

The alternator stator has nothing to do with the motor running. It only charges the battery. There is a separate coil for generating the ignition voltage.
 

cadet917

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Re: 87 25hp evinrude alternator

my digital meter has a 2k OHm setting... i guess that will work? there are some other symbols on it... is there a symbol for a diode test setting?
 

cadet917

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Re: 87 25hp evinrude alternator

it does have a diode setting, i will try it. i lost my analog meter and replaced it with this digital one but i will pick up another analog one because i do like those better.
 

F_R

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Re: 87 25hp evinrude alternator

my digital meter has a 2k OHm setting... i guess that will work? there are some other symbols on it... is there a symbol for a diode test setting?

The universal symbol for a diode is an arrowhead pointing to a line. Ignore the A and B, picture borrowed from another drawng.
 

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cadet917

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Re: 87 25hp evinrude alternator

i dont think the stator is bad since the engine runs fine... i dont get any increase in voltage on the battery when the motor is running so im pretty sure its the rectifier. I had a problem with the ground connection on the battery a few weeks ago which may have damaged it. i ordered one from iboats today for $30.
 

cadet917

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Re: 87 25hp evinrude alternator

i got the new rectifier and installed it... didnt fix jack. Im ready to junk this thing !! what else could be causing the low voltage?
 

wilde1j

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Re: 87 25hp evinrude alternator

Stator is typically composed of two functions parts: coils for providing ignition voltage and coils for alternator AC output to rectifier/regulator. These two are completely independent, they just happen to be mounted on a common piece of metal. You should have checked for AC voltage present to the R/R, before assuming the stator was OK. You should get > 30 VAC across the AC leads to the R/R.
 

cadet917

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Re: 87 25hp evinrude alternator

when i rev the motor im gettin 16volts back to the battery... im gonna let it run and see if the battery will charge. At low idle i dont get enough power back to the battery to charge it tho.
 
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