Converting Delco 28Si to external regulation

[nfluester]

awesome post, am looking to get a 28si for our volvo penta anyone know where to source a small diameter 6 groove pulley for the 22mm shaft on the 28SI?

[evm1024]

I got mine from Rod Collins but that path may be closed.

You should be able to source one from an alternator rebuilding shop in your area.

As I recall it is a K6 pulley.

[rsvmille]

Did you end up putting this on your 3ym30?

Thanks,
Ryan

[Scheperg]

Originally Posted by BlueHeeler

No worries. Glad to help.

"The alt kit cost about €600 and the 28SI was a bit over €200 including K8 pulley."

Hi Blue heeler, Where did you buy kit and K8 pulley. I'm doing same install need 24/150A alternator with kit.

All help appreciated

[pswired]

Thank you for all the valuable info in this thread. I have just installed a 900AH lithium bank in my Tiara and have Balmar 95 series alternators from 2002 that need to be rebuilt. While searching for new alternators, I was disappointed to find that the choices seemed to be either cheap automotive models with little to no info on duty cycle, expensive marine-specific models, or large frame units that wouldn't fit my application (Cat 3126B J180 short/fixed mount). I was very happy to find the 28si and ordered one for $264 from here:

https://www.jittruckparts.com/delco-...rnator-8600312

My only complaint was that there doesn't seem to be a dummy regulator available for external regulator conversion, like everyone here has found. I wanted to show how I converted to external regulation, since it might be simpler than building the terminal mounting board like others have done. Note that I don't need a tach connection in my application so I omitted that part.

First I removed the OEM regulator from the alternator using the instructions from others here. Then I opened the regulator by cutting the RTV seal around the rear access panel and prying the lid off, which exposed the control board:



I then clipped all of the connections between the terminals and the board using wire cutters, including the conenction between the unrectfied output (the soldered-on terminal on the outside of the regulator) and the R terminal. Finally, I soldered a piece of wire between the field terminal connection and the R terminal post:



This converts what was the R terminal post to a field terminal. Finally, I potted everything back up with some epoxy:



No high temp wire or other new connections needed. Just need to relabel the R terminal to "Field" on the outside of the unit and add a label indicating that it's now set up for external regulation, and it should be good to go!

[sailingharry]

PSWired, I don't have a 28SI (won't fit, I've tried), but this sort of short, clear documentation, complete with pictures, is wonderfully helpful for those looking to make a conversion like this today, tomorrow, or 5 years from now!


And your out-of-the-box thinking makes a far neater and safer solution than "fish a wire in" trick. I did that on the 12SI on my old boat, and your solution is much nicer.

[pswired]

Thanks, sailingharry, I hope this is helpful.

I also took some thermal images of the 28si at idle and wanted to share them here. This might help someone decide where to put their temperature sensor.

From high to low temp: stator windings, stator core, rectifier assembly, everything else. Temps in the pics are in deg F.