Alternator question

[George Forrer]

I think I need a new one. Mine is only putting out 12.5 volts at all rpm ranges. I only
see two listed. The motor is a 2006 QSC 540hp. So I am thinking that I should be
ordering a 22SI is that correct ? Not sure what the current amps are for the old one
looks like a 3 wire from the picture. I think the 130 amp should do just fine. Thanks
for the help. George

Topic

[George Forrer]

Ok see if any of these help. The close up one of the turbo shows some soot is that something
I should be looking in to.

[Rob Schepis]

No, I don’t think sweating is the major factor here, I think the engine room vents should be inspected carefully for salt spray coming through. Nice boat that Post, great lines. They do have those big hull-side vents so do give them a good inspection.

[Tony Athens]

This is what you have:

An aftermarket (that does not mean good or bad) Delco style 21SI 3-wire alternator that is be “SPRAYED” with salt water.. It also has a way undersized wire going (maybe 10 ga? ) from of output of the alternator to “most likely” the starter………….None of what I see was Cummins supplied, or will give you good service, especially the “salt water thing”..
……………………………………..No alternator made will survive that for very long……..Can I “see” the rest of you engine?…………….

Tony

[George Forrer]

Here are the pics of the alternator. A guy in the marina saw me taking it for and said there was
a shop down the road that could fix it. So I gave it a shot. Dropped it off at 3pm and at 4:30 the
guy called and said it was ready. I asked how much he said $30. He replaced one brush. Said
it looked like it got a little wet. Tony you can tell a lot from a pic. Still want to get a new one.
I think he wrote SI 22 on the tag.

Rob I will take some pics in a couple of days. I don’t think there is any box. The boat is a 43 Post
1987 it was repowered in 2006. I bought it last July so I don’t have a lot of history with it.
Also I see you are here in the north east. Do you think the motor could be sweating? The water
under the boat is 60 and the air for a couple of days was 90. Thanks for the help guys
George

[Rob Schepis]

ER Vent

Sounds like the ER vent is positioned where it could see spray. Does it include a dorade box ? Any pics – exterior &/or interior ?

[Tony Athens]

I cannot think of any alternator that will will survive heavily salt laden air being sucked thru it for very long….That’s what alternators do–They suck ambient/local air thru them for cooling..

Keep that in mind for the future.. Maybe an alternative source for ventilation so as to reduce the velocity/volume of the air coming thru that vent on that side or in that area??

Tony

[George Forrer]

Thanks I will take it off on Monday and post the pics. The engine room is dry but
that is the out board side of the motor and close to the air intake in the hull.

[Tony Athens]

Alternator Issues

George,

You picture does confirm some things but being a 3-wire alternator is NOT one of them ..

1) It confirms that this alternator has already been replaced ( something aftermarket)

2) It does look Delco 21/22I- ish

3) It confirms that is is being misted with salt water, and / or is operating is a very wet atmosphere.

4) Go here and get a picture just like this:

Cummins Marine Delco Style Alternators – Identification

at this angle or perspective..

Let’s now go to step two & get you sorted out..

Tony

[Author]

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