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Unread 04-10-2010, 09:51 PM
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scook scook is offline
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Join Date: Jul 2005
Location: Portland, OR
Posts: 1,432
Default Mercruiser 170 Alternator Questions

Anyone know old Mercruiser 170 electrical???

Engine is a Mercruiser 170, I/O, SN 6916938, in my '85 V-20 with the alternator integrated on the front of the engine. The commutator, holding the magnets is what would normally be the crankshaft pulley. My manuals don't show this configuration - I don't think they used it much.


I pulled the alternator off to get at the coolant circulating pump and have a question about putting the magnets back into the commutator housing. The stator and commutator were really rusted and the magnets were detached from the housing, so I cleaned and treated for rust/corrosion and need to reinstall the magnets. They were adhered with some kind of glue, but I can't tell what it was.

Questions:

1 - Should the magnets be evenly spaced around the commutator housing? They weren't, and it was charging fine, but it seems to me they probably should be???

2 - What adhesive should I use to hold the magnets in?


3 - I checked the resistance of the stator and got .2 Ohms - is that OK?

4 - The windings are corroded, probably 1/3 of the wire in a couple of locations - is that going to generate hot spots? If so, is there a repair I can do, e.g. add some solder, separate & splice the wire . . . (being careful to maintain the insulation)?

The Salmon are running, and I'm pawing the ground to get it back together, but I don't want to screw it up at this point.

The Stator, cleaned up and coils re-varnished




Commutator cleaned up & painted, with magnets placed, but not glued in



Thanks - Scott

By the way - Thanks to MJ for this great newer site - the pictures are a snap and it really works smoothly compared to the old one.



Below, if anyone's interested, is a puller I made from an old beam hanger, one Saturday, to get the crank pulley/commutator off. I ended up having to put about 6" of thread on a 3/4" bolt with a chase nut, but it worked.

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Scott, Portland, OR '85 V-20 I/O, Merc 170
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