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Installing an Electromaax Alternator in a Beneteau 50 with a Yanmar 4JH3-THE

Yanmar Install On Beneteau

Upgrading the alternator is one of the best economical choices you can make

Having a particular boat with a particular engine means wanting some specific directions when it comes to something like replacing or installing a new alternator. Electromaax is often rated one of the best and is certainly one of the most common ways to “upgrade” your boat.

When it comes to upgrading your alternator

Upgrading the alternator is one of the best economical choices you can make when it comes to your boat, yacht, or seaworthy vessel. It is certainly the case for your Beneteau 50. High output alternators create more electricity and make it available out at sea. This gives you more power for everything, from electronics and windlass to lighting, AC appliances, as well as refrigerators and water makers. Electromaax and other high output alternators produce as much as four times the power of other alternators. They are practically necessary for cruisers.

In the case of a new Electromaax alternator for a Beneteau 50, the standard one that you are likely replacing is an 80a Hitachi alternator. If you want to improve the charging capacity of the whole electrical system, replacing it with a 140a Electromaax along with a new serpentine belt kit will make a lot of sense.

Removing the current alternator

The first thing you are going to do is extract the current alternator and belts. In this case, attached to the crank is a harmonic balancer. The outer pulleys that are used for the fridge compressor will actually be tapping into that. You will want to take that harmonic balancer by unscrewing the 6 hex head nuts that are holding it in place. In the case of the Yanmar 4JH3-THE, the bottom crank pulley actually fits over the top of the pulley that is currently there. So you can leave the large bolt at the base of that pulley in place. Just realign the holes and slide the serpentine belt pulley that is at the bottom onto the existing crankshaft.

Next step, install the crank pulley with two bolts, then unscrew them and install the harmonic balancer with six bolts. Tighten them as you would most other bolts, which means tighten as much as you can and then take up a little slack. You might need to loosen the bolts on the water pump pulley a little because the alternator belt is still on and the pump will spin and spin easily, which may cause an issue during this process. On the other hand, don’t unloosen the 23mm nut that is holding the crankshaft to the pulley. That could cause problems.

Finally, you will actually detach the current alternator. Fortunately the Hitachi alternator is only connected with four simple bolts, so easy enough. Installation of the new alternator is a different thing.


The first step in this process involves installing the new Electromaax to the saddle connection. Electromaax comes with a relatively small-diameter bolt, but a longer bolt compared to what you are likely to find with your previous alternator. It should come with bushings that can help with this.

Next, connect the field wire with the regulator. If possible connect the wiring harness directly. Make sure and put an Ancor 2/0 cable in between the wiring harness and a house battery bank using a Blue Sea Systems Fuse, 225 amp. If you find that you are not getting much of any power yet, one trick is to run a wire, 12 volts, from the positive battery post to pin seven of the Balmar 614 regulator. This may magically result in the higher volts and amps that you would expect.

Then install the Balmar regulator somewhere safe and where there aren’t any other electronic parts.

Finally, you are likely to want to get the engine-driven fridge belt adjusted. In fact, this is actually quite simple in this particular situation. You can switch the refrigerator from the inner pulley to the outer pulley. This fixes the problem.

In the end, this new alternator install should allow for over 13 volts at close to 1000 RPMs. One benefit to keep in mind is that by tossing the old battery isolator, the amps and volts gained are going directly into the house battery bank. This improves battery depletion significantly.

The Benefits

There are a great number of benefits that can be enjoyed once you do have this high output alternator available. Alternatives are likely to die on you more often than not. If too many devices are trying to power off of this one source, it’s going to become a problem. In this day and age, having multiple devices on top of the ones that are normal for Beneteau 50s plugged in and extracting power is almost inevitable. Rather than monitoring your power usage, having the ability to use what you need is nice.

And the longevity of high output alternators is particularly impressive as well. When it comes to high output alternators, you are talking about heavy gauge wiring that allows more current to pass to the components. The alternator efficiency is affected significantly as well as this eliminates the possibility of undercharging.

This all affects longevity. Longevity means saving money over the long term. High output alternators tend to be more efficient than their alternatives and they dissipate heat more evenly, which means the alternator itself doesn’t get too hot. It is safer and more economical. In the long run, for all these reasons and more, making the switch and installing things correctly will be a great investment for the future.