Bad Alternator?

[TXSurf4]

So quick question before I pull the boat. I ran the boat all weekend and it ran awesome, on Sunday we surfed the early morning golden hour with all the lights on and everything. Around lunch we went to head back to the lift and got a message on the screen saying low battery voltage accelerate to 1500rpm. I was already running 4200 so I new something was wrong. I clicked to the battery voltage and saw it said 11 volts, I kept my speed up and luckily I was able to get back to my dock and get it on the lift. After doing that I tried to crank the boat and as I expected didn’t have enough juice to start. In my gut I said probably the alternator but being that our lake house is 2.5 hrs from our dealer I wanted to exhaust all options. So I pulled the batteries and swapped them both in hopes that I had a weak battery and that would fix it. Well she fired up no problem but the voltage on the screen read 12v so I check my voltage at the alternator using my volt meter on the 2 leads and it read 11.8v which I assume is just the voltage of the batteries in the circuit. So am I correct in my next step of getting my alternator replaced? Or is there something else I should be looking at?


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[HFarr]

Cannot say for sure on this system because I have not checked it, but most alternators put out about 14 volts when running/charging.

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[vdubnick]

have you checked the obvious (belt)? i would assume you would have overheated if the serp belt fell off, but its a quick check. Also, check connections at the alt. if there is a loose connection that would explain it as well. I doubt the alternator is already bad, but strange things can happen.

check all the simple stuff before you go swapping alts. could just be the signal wire at the alt.

[larry_arizona]

The good news an alternator swap on a raptor is as easy as it gets.

If I recall, 2019 SC had alternator issues. Not positive it was on Moombas, but 100% sure the Supra 230 amp alternators were wired wrong and it caused a recall.


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[HFarr]

Don't forget to check fuses and tripped breakers

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[TXSurf4]

Ya all the connections are good on the alt and the belt is good as well. If the belt had popped I definitely would have had an over heating issue as once we were done surfing I hit "Go Home Leveling" and got her on step headed back to our dock. The warning popped up about 2 mins in to our trip back and we still had about 8 mins left back to our dock. I would be worried about the fuses and breakers if the alt was putting out 14V but it seems to me that since I saw 11.8V (which I assume is the 12V off of the batteries) at the alt that the circuit between the batteries and the alt is in tact. Am I wrong in thinking that the 11.8V I saw on my multimeter is the voltage coming off of the battery?

Larry you are correct there was a recall back in 2019. IIRC I believe it only affected the Moombas with the 450 and then all of the Supras. I had mine replaced right before Memorial Day back in 2019. It was a scramble when Indmar announced that back then but luckily my dealer ordered one for every boat they had in stock and that they had sold as soon as it was announced so we were not down long at all.

[vdubnick]

Ya all the connections are good on the alt and the belt is good as well. If the belt had popped I definitely would have had an over heating issue as once we were done surfing I hit "Go Home Leveling" and got her on step headed back to our dock. The warning popped up about 2 mins in to our trip back and we still had about 8 mins left back to our dock. I would be worried about the fuses and breakers if the alt was putting out 14V but it seems to me that since I saw 11.8V (which I assume is the 12V off of the batteries) at the alt that the circuit between the batteries and the alt is in tact. Am I wrong in thinking that the 11.8V I saw on my multimeter is the voltage coming off of the battery?

no i think you are right about the voltage being battery... which is good you are getting it at the alt, that means you probably have good continuity between them.

where did you measure on the alt? if you were touching the stud or nut on the alt i would say it is safe to assume connection is good, if you measured on the ring terminal or cable then it is possible there is bad connection.

only other thing i can think of to check is the signal wire at the alternator. if it isnt getting voltage, the alternator will not charge coils and will not output voltage. if it is getting voltage, then i would assume the alternator is bad.

[TXSurf4]

no i think you are right about the voltage being battery... which is good you are getting it at the alt, that means you probably have good continuity between them.

where did you measure on the alt? if you were touching the stud or nut on the alt i would say it is safe to assume connection is good, if you measured on the ring terminal or cable then it is possible there is bad connection.

only other thing i can think of to check is the signal wire at the alternator. if it isnt getting voltage, the alternator will not charge coils and will not output voltage. if it is getting voltage, then i would assume the alternator is bad.

Ya I measure it a few times touching various points on the alternator including the studs and nuts. Is the signal wire the plug connection on the alt?

[vdubnick]

Ya I measure it a few times touching various points on the alternator including the studs and nuts. Is the signal wire the plug connection on the alt?

im not 100% familiar with this alt, i havent looked close on mine, but yeah, usually it is a plug or small terminal with small gauge wire.

[TXSurf4]

im not 100% familiar with this alt, i havent looked close on mine, but yeah, usually it is a plug or small terminal with small gauge wire.

I know there is a plug. So would I just fire it up again with the plug unplugged and just check voltage on the plugs side or the plug connection on the alternator?