Diesel and electric inboarder in catamaran stb/port ?

[Joeedelcat]

Hello
Has anyone experience with using a catamaran with one side diesel inboard and the other side electric inboard ?
I do own a 43 foot lightweight catamaran. Unfortunately one 40 hp inboard is deadly sick. So I think about using the existing saildrive and hooking on a 48 V Motenergy brushed 10 hp motor just for movability purpose. For cruising the diesel inboard is plenty.
Anybody done something similiar and would share their experiences ?
Thanks
Joeedelcat

[GrowleyMonster]

Originally Posted by Joeedelcat

Hello
Has anyone experience with using a catamaran with one side diesel inboard and the other side electric inboard ?
I do own a 43 foot lightweight catamaran. Unfortunately one 40 hp inboard is deadly sick. So I think about using the existing saildrive and hooking on a 48 V Motenergy brushed 10 hp motor just for movability purpose. For cruising the diesel inboard is plenty.
Anybody done something similiar and would share their experiences ?
Thanks
Joeedelcat

I love electric propulsion for many reasons, especially as auxillary propulsion for a sailboat. I have some reservations about what you are contemplating, though.

Yes, since it is only pushing half of a catamaran, a 10kw or 12kw motor would be sufficient for docking, maneuvering, etc. However, for motoring of any real distance, a large battery bank is needed. Your batteries will weigh twice what a replacement diesel and fuel tank would weigh. Also it would be quite a feat of Rube Goldberg engineering to integrate the electric drive with your installed throttle controls. A separate knob next to the throttle levers would be a bit awkward and inelegant. No cat expert here, and I know it has been done, but I am not too sure that long distance motoring of a cat with one engine is a workable long term solution.

Is the other diesel likely to fail soon? A complete repower could be an owner project, or could be done professionally, for considerably less than new diesels. Remember that speed, range, or battery bank size, one of the three, can be optimized a bit at the expense of the others, but you don't get all three. For occasional long distance motoring, a genset could keep the batteries up, but this is not very efficient. Even on a cat, it is not really practical to mount enough solar panels to charge a big enough bank to run all night.. mast and sails and other stuff shading the panels sure doesn't help. Regen from the trailing props can stuff a bit of power into the batteries, when you are sailing fast and if you don't have folding props, at some loss of speed. Takes several days minimum, over a week maybe, depending on house loads, to bring a heavily discharged bank back to full. If you only need propulsion for short periods, a total repower might be a good bet. However, if the other diesel is in good shape, I would replace the dead/dying one with another diesel of similar power. Perhaps used.

If keeping resale value up is important, be aware that buyers and new owners don't as a rule like anything new or unfamiliar. Electric drive will discourage many buyers, and fail to satisfy many new owners who do not understand electric. It is often said that modern e-drives are maintenance free. However, there is indeed a fair bit of maintenance to be done with the batteries. Batteries, especially lead acid, are sensitive to deep discharge, and a few discharges to 20% can kill batts. They must be kept watered. They need to be equalized at least once or twice a year. And even with the most careful maintenance, they nearly always need replacing by their 10th season. Idealists find that the reality of having a double digit range at modest speeds takes the luster off the dream of clean, environmentally friendly propulsion.

There are benefits of electric propulsion. Instantly available power, for one, with no starting and no warmup, which can be handy for maneuvering even with the sails up. Electro-tacking makes tacking in the most hardmouthed boats a breeze even single handed. You can pinch really close, even in light airs. Electro-sailing in very light airs can keep you moving with very modest power consumption. You never have to cross your fingers and hope your engines start. You don't have to buy fuel, clean up spilled fuel, pay for fuel, smell fuel. Electric is quiet. With brushless motors, motor and controller maintenance is generally zero. There is no minimum idle speed, so you can ghost into your slip at 40rpm instead of bumping ahead or astern with the clutch. This is especially helpful when backing into a slip. Your eco footprint is as small as it gets, without resorting to paddles. Don't let the glowing picture distract you from considering the cons, though. Maybe it is for you. Maybe not.