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Q for the outboard mechanics


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I’ve got a 2002 Merc 50hp 2-stroke.  Runs great.  Started no problem yesterday, but was a bear to start this morning (cool out, not cold).  But then started immediately this afternoon.  We ran about 10min at full throttle for fishing this afternoon, and noticed an electrical/rubber smell.  Motor started right up and ran great for the run home, but I realized the smell was definitely from the motor.  Pulled the cover off at home and found a hole melted in the rubber face of a part, and looked like a bit of ash inside.  Can anyone tell me what this part is?

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Not 100% sure, but it appears to be the rev limiter. Goes for about $187.00.   Please understand I am NOT totally sure, so I hope someone more qualified than I am will chime in with more info.

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Some advice led me to a parts diagram - turns out the part that's fried is the voltage rectifier/regulator.  Looks like an easy part to install myself. Cost is about $150+ for the OEM part, or $30 off Amazon. I'll try the Chinese option - fingers crossed.  lol

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3 hours ago, The Baron said:

Some advice led me to a parts diagram - turns out the part that's fried is the voltage rectifier/regulator.  Looks like an easy part to install myself. Cost is about $150+ for the OEM part, or $30 off Amazon. I'll try the Chinese option - fingers crossed.  lol

That would make it hard to crank, might explain why it had trouble . Same thing went out on mine and I had to floated 5-6 miles downstream dodging pleasure boats and laydowns with a paddle haha. @galyonjreplaced mine, how’s that for a cool friend???

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Couple words of wisdom.  Close to where that part is, there's a 20 amp fuse plugged into the wiring harness.  Check that fuse and make sure it is a 20 amp and someone hasn't replaced it with a larger fuse.  That fuse is there to help protect the Rec/Reg.  When it blows, you loose all electrical power from the motor and too many times I've seen people put a larger fuse in.

95% of the time when you fry the REC/REG, it's because you have a bad battery and the rec/reg is over worked trying to charge it.  That could also explain the hard to start.  

A lot of people have a hard time comprehending just because the motor is cranking over the battery could still be junk.  The motor is cranking but it may be cranking to slow to provide enough spark to fire the plugs and pulling the voltage down too low on the other electrical.  

Jumping the battery off because it was too weak, and letting the motor try charging it will blow the Rec/Reg, it's not designed to be a battery charger, more of a battery maintainer.

It would be wise for you to pull the battery, and have it tested, or you can just blow this off and think BS, there's nothing wrong with my battery, but do and there's a good chance you will be buying this part again.   

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Whike your in there, it appears you have some connectuons with some crud on them.  Take them apart and clean them, I use a small brass brush to make them shiney, add a dab of dialectric grease then tighten things back down fairly tight.  Boat electrical connections grt alot of jostling around so they need to be clean and tight !!  Loose connections can cause even more issues from intermitent connecting and sparks. Good luck...

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On 9/18/2023 at 11:25 AM, Way2slow said:

95% of the time when you fry the REC/REG, it's because you have a bad battery and the rec/reg is over worked trying to charge it.  That could also explain the hard to start.  

It would be wise for you to pull the battery, and have it tested, or you can just blow this off and think BS, there's nothing wrong with my battery, but do and there's a good chance you will be buying this part again.   

I appreciate the good advice.  When I went to charge the battery Sunday night, the charger display read “Lo”.  I used the restore function and it took a full charge.  I got the battery tested today and it showed 12.6v, ok for cranking but it failed for reserve.  So either the battery was tired to begin with and/or the extremely hard start on Sunday ran it down too low.  Either way, the battery is 5 years old so I can’t complain too much.  I bought a new one today.
 

My Chinese voltage regulator is due to arrive today.  I pulled the old one and it is indeed marked 883072.  The one I ordered specifically lists as a replacement for that part, so i should be all ready to install the new part and test ASAP.  Hopefully I’m right back out for the fall bite soon.

 

I will update soon with the end of the story (hopefully a happy ending).??

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Don't forget to check that fuse and make sure it is a 20 amp.  In the ideal world it was supposed to have blown to prevent the REC/REG from burning out because of have to put out more current that it was happy with.  Also, it would pay you to keep a couple of those as spare fuses on the boat.  Just letting a good battery get discharged and the motor trying to charge it can blow that fuse.  That's whey the unknowing stick a larger fuse in.  I guess they figure the $135 reg is cheaper than a 50 cent fuse.

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@Way2slow - thank you for the reminder.  Pretty sure I found the fuse along that system of wires, and it is indeed a 20amp.?

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Update - all good news.  The motor started right away this cool morning, and ran like a top.  I ran WOT for 5-7 minutes a few times.  Idled a bit, and low throttle a bit.  Started immediately every time.  Popped the cover at home and the new Chinese voltage regulator looks good.  Put the batter charger on the new cranking battery and battery was still reading 100% and 14.4v so no signs of trouble there.  Thank you all for the help!

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Glad you got it solved. Also glad you checked with others and a parts diagram so you did not buy a rev limiter like I suspected it could be. As I said, I am not by any means a marine motor expert.....

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