Blue Circle alternator and tach calibration

[Kyle Ewing]

I upgraded to the Blue Circle alternator and ARS-4 regulator from the stock 55 amp alternator.  I found reference to the new alternator having the same number of poles so no tach adjustment should be necessary.  For those who replaced the alternator did the tachometer read the same or did you have to adjust the tach due to another variable (i.e. pully size)?  The reason I ask is I also replaced the prop with the Kiwi-prop with different pitch from my fixed 3-blade I want to accurately judge engine load.  At dock the engine's maximum RPMs are lower, even in neutral.  I have the M25xp.

Kyle Ewing
Donnybrook #1010

[Ron Hill]

Kyle : I seriously doubt if the pulley on your new alternator is the exact same size as the old pulley on your Motorola 55 amp alternator --- hence your Teleflex tac is not reading correctly.  The number of poles may be the same, but.
There are at least 2 articles that I wrote in the Mainsheet Tech notes telling readers where to call and get the formula to calculate the correct dip switch settings for your engine tac. 

I'm writting this at anchor, so you'll have to do the research !!    

[Craig Illman]

Kyle - The Teleflex tach manuals are available in the Manuals section of this site. http://www.c34.org/manuals/index.htm It's not too difficult to do. The challenge you have now is to get a good reference. There's supposedly a trick you can do with a 120V flourescent light, but I didn't have any sucess with that approach. You might se if your local tool rental has a manual tach available.

Craig

[Ray & Sandy Erps]

I did that upgrade a few years ago and I seem to recall that there was an adjustment screw on the backside of the tach for the fine adjustment.  I noted the high rpm and idle rpm setting before the change over and then adjusted the tach as close as I could to those previous settings.

By the way, what is that fellow getting for his alternator now? 

[Stu Jackson]

Just don't sweat it, it makes absolutely NO difference, Kyle.  We did that swap and it actually reads what I would consider to be more "accurate" than the old Motorola.  Engine in neutral, max rpms were 3000, in gear 2700.  New alternator max out of gear 3200, in gear 3000.  Do I really care?j  What i spend time doing is finding the "sweet spots" when the engine's on, and avoiding those gnarly rumble rumble tank tank spots that sound horrible.  2,158.00 engine hours, 1,848 when I put the new Blue Seas alternator in.

[Kyle Ewing]

Thanks all for your responses.  I found max RPM with the new Kiwi-prop under way is 3200.  With the old 15x9 prop it'd turn 3600.  Tied to dock the engine turns much slower, only 2700 vs. 3200 for the old prop.  I was initially worried that the prop was over pitched.  I feel better that my numbers match Stu's and agree that at this point it's not worth fussing with.

Ray, the alternator is now $140.  With shipping to Chicago the total was $153.

The alternator and regulator upgrade was straight forward.  Everything written here helped.  One of these days I'll write up what I did--upgraded the alternator and regulator while adding a dedicated starter battery (Optima 34M) under the rear berth charged with an Echo charge.  The Optima 34M is shorter than a led acid battery and can be mounted in any position which greatly simplified mounting.

[Stu Jackson]

Good input, Kyle.  See my November 2006 article in mainsheet about that same alternator/regulator replacement.

[pjcomeau]

Where do we find Tech notes after 2005? The spreadsheet ends with Nov 2006, but the link brings a file not found. I'm logged in and can see earlier notes.

Thanks

[Stu Jackson]

Pierre, I'm still working on getting those tech notes online in color (in lieu of the old black and white scanned PDF files).  If you're a newer member and would like (or need) a specific article, email me and I'll get it to you. (As a C34IA member, you get access to the TNOs and the hard copy Mainsheet magazine.