New Alternator

LeslieTroyer · Aug 10, 2019

Both seem way too expensive. How many amps are each?? You might be better off with one from Compass marine (marinehowto.com) or taking your existing alternator to an Auto Electric shop for rebuild.

jviss · Aug 10, 2019

Jac123 said:
Boat yard says $640 for o.e.m./$395 for aftermarket

Is that the price installed, parts and labor, or just the part?

I assume you had the stock, internally regulated, relatively small output, like 35 to 55 A?

jviss · Aug 10, 2019

There can be quite a variation in quality for alternators, from pretty cheap stuff to high quality, name brand stuff.

What engine do you have, and what make and model alternator are we talking about?

Are you planning on installing it yourself? Know what you're doing?

shemandr · Aug 10, 2019

I think that's very high. When I fried mine the replacement was around $150 - just a little more expensive than the rebuild. It was OEM, I think, but nothing fancy. I wanted a drop in replacement. It was for a Mercruiser, which is a popular motor, and probably a larger market. Nevertheless .... $640? Price check that. PM me and I'll give you a source.

RitSim · Aug 10, 2019

We had a 1989 Catalina 30. When the Motorola alternator died, I bought a truck alternator from "Discount Starter and Alternator" for $80. I added the tach connection by opening the rear cover and using nylon insulators from the hardware store and adding a wire from one of the diodes. I think they now offer a marine version- don't know if they have the tach connection. Used it for 8 years - no problems. I did need to add an "idiot light" on one of the field connections. You can replace the quoted alternator 8 times for the same price,

jssailem · Aug 10, 2019

@Jac123 That is a high price to pay for a basic alternator.

It might be in your best interests to learn about alternators. How they make you boating life better and how the wrong one can ruin your batteries early in their lives. Two good places to start are @Maine Sail ’s website https://marinehowto.com/marine-alternator-installation-tips-tricks/

And @Stu Jackson ’s posts about Catalina electrical systems Boat Electrical systems “101” where he has shared a lifetime of electrical solutions on Catalina boats.

Like @LeslieTroyer suggested, you’ll find a quality alternator and a very fair price that may last as long as you own your boat from Maine Sails’ site. I bought my replacement there and extremely satisfied. It is rated for 105 amps as compared to the 55 amps of my OEM unit.

You have identified a key issue with your “alternator system”
“Mounting Hole in bracket is oval so it continues to slip.”
Maine Sail shared that is one of critical issues missed by most yards and boat owners. “It is up to the installer to properly secure the alternator in place.” Most installer fail to use the proper bolts, bushings or shims to secure and align the alternator. You are going to need to remedy this problem or you will have an early failure of any new alternator you purchase. MaineSail provides the proper bolts and bushings with his package to help with the install. It is still up to the installer to get it right.

leo310 · Aug 10, 2019

Take a look at https://www.dbelectrical.com/alternators/marine/westerbeke/ and Amazon they start at $100 and up

LeslieTroyer · Aug 10, 2019

Jac123 said:
Going with aftermarket- thanks to all

Make sure you get one with AC or tach output.

Benny17441 · Aug 10, 2019

The OEM is good quality and most will last many years. The aftermarkets vary in quality from good to junk. If the problem is the mounting hole drill and install a bushing and replace bracket. I would rather rebuild an OEM alternator than take chances on an aftermarket; check with an electrical shop in your area,

Maine Sail · Aug 11, 2019

For future reference the CMI-72-IR (also available in an externally regulated version CMI-72-ER) was designed specifically as a replacement 72A alternator for Catalina's or other boats where the OEM Motorola 51A (now discontinued) or 55A (only Chinese clones now available other than some left over NOS units) was originally fit. The 72A stator/rotor combo was chosen to work in concert with the factory 3/8" belt and maximize amperage output while minimizing belt dust. The internal voltage regulator can be pre-set (not field adjustable) during bench testing to your desired value. It is also very reasonably priced.

CMI-72-IR