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79’ski nauti possible alternator issue |
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key1977 
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 Topic: 79’ski nauti possible alternator issuePosted: September-10-2020 at 1:48pm |
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Boat just sat for a month. Had trickle charger on motor battery and one on 2 radio batteries. Had trouble starting. Very sluggish just on motor battery. Switched over to use both the motor battery and radio batteries for cranking. Finally got it going. Stopped at advance and got new battery for motor. Get to lake and wouldn’t spin starter fast enough to start. So i switched to use all three. Got it started. Took off across the lake. Throwed the anchor and sat maybe an hour. Go to start. Again to sluggish to start. Switched to use all three again and it all was dying. Had to get a jump to get it back to dock. Took it home. Had a guy check for me. Diodes seem to e ok according to him. But alternator was only putting out 12.5. Hes thinking alternator is week. It rang a bell that i believe a few years back i had it rebuilt. My question is does someone have a link to a brand new one ? The alternator advanced had a few years back didnt have 4 wires. Everything ive searched for is 1,2 or 3 wire. Hell ,.... i would even put a high out put in it if i could get 4 wire.
It has new coil and starter last year cause of starting issues. Tired of being jumped off. Any help is MUCH appreciated. Thanks. |
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KENO
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Posted: September-10-2020 at 3:29pm |
Was the "guy" from an auto electric shop or just somebody wandering by?  How'd he decide the diodes were good? Or that the alternator was weak? If your 79 is a PCM 351, and it has the original alternator, it's a Prestolite and like you said it has 4 wires. You made no mention of a voltage regulator hanging out at the back of the engine. It would resemble this one in the picture One doesn't work too good without the other, so if your regulator is bad and your alternator is good, you'll have charging issues You can still find a regulator to work with the alternator, the alternators are long since out of production but an auto electric shop should be able to help you out  Here's a picture of the back of the same regulator with a part number. This was an aftermarket regulator, the wire colors may be different but it's pretty easy to compare and make sure it's wired right. The original had Green, Brown, Black and Orange. This particular aftermarket one Green, Brown, Black and Purple  |
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8122pbrainard
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Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Posted: September-10-2020 at 8:10pm |
Scott, I suggest getting the batteries load tested. "Trickle" chargers are not designed to be kept on batteries for any length of time. They don't taper the charge down to a point that won't damage a battery. Battery maintainers are a better way to keep batteries up to a charge. Do you have a parasitic problem that drains your battery and the reason for the chargers?
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key1977
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Posted: September-11-2020 at 10:32am |
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I will check style of chargers this weekend. Found a site with regulator. Is there a way to check if bad from home ? I may just order and swap out for new anyways. Shouldnt be to hard right ?
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KENO
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Posted: September-11-2020 at 11:56am |
When you have the engine running, you should have 13.5 to 14 volts or so at the battery terminals measured with a multimeter. If it's less, like the 12.5 that you mentioned, it's either the alternator or the regulator. In a little while, if I can scan and attach a couple of pages from a manual, you'll have a test procedure for the alternator and regulator. Me and scanners don't get along too good, but I'll get there. You didn't answer those questions from earlier, so hopefully you have a PCM engine.
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key1977
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Posted: September-11-2020 at 12:19pm |
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Sorry. I was having issues replying. Its the 351 ford. 👍🏼
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KENO
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Posted: September-11-2020 at 12:29pm |
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2 pages from a PCM manual for testing the alternator and regulator. 
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key1977
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Posted: September-11-2020 at 12:44pm |
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Thanks !!! 👍🏼
I will have the guy that walked by read up on this. 😉🤣 this weekend. |
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KENO
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Posted: September-11-2020 at 12:49pm |
A most excellent plan
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key1977
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Posted: September-11-2020 at 1:04pm |
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Blurry as heck. If i cant read it i know he wont be able to. Saved to my photos and zoomed in. No chance of reading it this way. 🤷🏻♂️Sorry
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key1977
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Posted: September-11-2020 at 1:57pm |
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Got a new regulator on the way. Ebay find. No picture was provided. But was correct part number. Would you have part number for alternator??
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KENO
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Posted: September-11-2020 at 2:40pm |
Send me an e mail and I'll send you a return e mail that should be easier to read........especially if you're on a real computer keno439@gmail.com
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KENO
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Posted: September-11-2020 at 2:53pm |
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The PCM part number for the alternator was RA097002 and it's no longer available.
If you do a search on that number, a lot of places will sell you something newer and different with an internal regulator that takes some wiring changes. Some take more changes than others, none are too hard though. PS you have a return e mail |
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key1977
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Posted: September-22-2020 at 10:02am |
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So far so good with new regulator. Been going out to the shop each day and she fires up. 😎 🤞
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key1977
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Posted: September-22-2020 at 10:04am |
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Need to run it on the water to see if heat changes anything. 😬
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key1977 wrote: