Has anyone replaced their original Motorola alternator (which I believe is 35amp and no longer available) with one of the commonly available 51 amp units? I have previously had my Motorola unit rebuilt and have also had the diodes replaced. It is still charging, but the output is a little lower than it used to be. I am aware of Mainsail's recommendations, but my sailboat is a light use inland boat that does not justify the expenditure of major bucks. I have already removed the charging circuit from the original wiring harness and now go directly to the batteries with a Blue Sea combiner.
Universal M12 Diesel Engine
- Thread starter StanleyJ
- Start date
Louisville is a large city, and I betcha you can search out a little dusty shop that rebuilds starters and alternators. We have one or two in our metro area. Usually the guy has decades of experience and rebuildsan alternator inexpensively. Also can convert it for external regulation if you want. Our old Universal M25XP had a Moto that was about 50 amps, and was super reliable. If it needs a rebuild, that would be my first stop. I also had our starter rebuilt once, same shop. That made a noticeable difference in how fast it turned our engine!
Sounds like you have thought out your present "mature technology" charging system, and it suits you. (?) After all, the larger alternator would also need another HP or two to run when under load, and our small diesels often do not have any HP to spare......
Good luck!
Sounds like you have thought out your present "mature technology" charging system, and it suits you. (?) After all, the larger alternator would also need another HP or two to run when under load, and our small diesels often do not have any HP to spare......
Good luck!
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,741
I recommend contacting a local electrical shop. They can test your alternator using their equipment and, with their findings and your input, make recommendations. I did that in the first season of ownership. I was not looking to change anything on my boat until I had some experience with the systems. The shop owner tested the alternator. He had a rebuilt exact match model (you must get the same foot fittings on any replacement. They need to match the mount on the motor).I used the original model for several years and only changed it when I modified the boat's electrical system. You are happy with your present system, so either confirm that the alternator is up to the task or see what a rebuilt one can do to meet your charging needs.
You might consider adding solar panels to support your charging needs when you are not motoring or during anchoring times.
Different alternators can vary widely in efficiency, The Motorola 35A is a work horse which I would not consider replacing unless your batteries are not being fully charged or that they are not getting charged fast enough for your needs. The alternator is just one component on the system, older batteries could be the culprit in a weak charging system. Upgrading to a larger alternator is not all for the better. For example besides the cost, it takes horsepower to drive an alternator, a 35A alternator requires approx. 1.12 HP to drive it while a 55A alternator requires about 1.67 HP. That additional 1/2 HP could be or not significant for the size of your boat. Also the extra load will increase the wear and tear on the drive belt and could require a heavier belt. It is all about your electrical needs, if you really need an upgrade get a Motorola 55A but first check that your batteries and wiring are all in good shape.