Electric drive conversion

My brother and I have a 1977 32' Luhrs with [cough-cough] twin Crusader 454's (model 350's). We get an absurd 1NMGP with this setup, and we are severely limited by our 140 gallon capacity. We have been considering a diesel conversion, but I cannot help but wonder about an electric conversion.

Doing some crude research, it seems some 150hp motors could be purchased new in the ballpark of $5-6k. We would then also purchase a genset capable of driving both motors. From what I have been reading thus far, you would want 1/3 to 1/2 the electric horsepower of your current combustion horsepower, so two 150's should be sufficient.

I have seen several YouTube videos for smaller boats doing the conversion, but I am having a hard time finding anything near our size. Does anybody have any input on this? Resources to start researching more into the feasibility? Anybody actually done this?

I know it is possible, just wondering if it would be worth it over diesels.

Thoughts? Input? Experience?

Thanks in advance!

Well, about everyone I know that ever dealt with twins 454's has converted over to diesels for the very reason you want to do the same. As you probably know, the Navy has been using diesel-electrics for years, so it is possible. But these are backed up by massive battery systems. I do not have any direct experience doing this. Just a few observations from many, many years on the water

1. Electric motors and salt water do not go well together. Even motors that are "marine ready" will fail over time and a re-build is not usually worth the money. Replacement is the only viable option.
2. It is not just the motor itself that saltwater attacks, but every contact and connection in the electrical control system.
3. You will need a lot of electricity to run those motors at full power - over 220 KVA based on my calculations (300 HP X 746 watts/HP), and you will need a massive battery pack to act as a capacitor/regulator and backup.

I think diesels are a proven and much more reliable option.

I don't think the corrosion would be that big an issue with gasket-sealed totally enclosed (TEFC) motors. I mean, any worse than the cast iron blocks we have right now? The terminals should be no harder to maintain than the gauges on the fly bridge, battery wiring, breaker box, and such. They could be tinned even. Batteries should be okay, I would think, with the space saved from removing these ginormous Crusaders. 18 batteries in series would give the required voltage, but amps? Maybe 36 golf cart batteries in series-parallel?

For a generator... am I seeing that conversion correctly that even two 75hp motors would require ~112kW?!?! That might be the deal killer there, eh? That's one serious generator to stick in the back of a 32-footer. Is that even possible?

The reason this has piqued my interest is the things I have seen lately. Cruise ship a few months back was electric/hybrid. Boat that took us to Alcatraz two weeks ago was electric/hybrid. I work for Honda, and we now have a plug-in hybrid Accord that is electrically driven. My mom just bought one last week, and it is surprisingly quick and getting 64mpg on gas. This all tells me it is possible.... but possible in OUR boat?!

Many of the modern ships are now diesel electrics - a diesel run generator powering electric drive motors. Sometimes they are integrated with turbines. But they are huge diesels and generators. Try to arrange a tour of one of the new cruise ships or navy ships that are set up that way. Last one I saw was several years ago - it was one of the new Navy destroyers.

I did a quick scan in the Internet and see that there are all kinds of conversion kits and discussions. So, you might me on to something. But getting 300 HP on a 32' boat is likely to be a real challange.

Let us know what you find. You've certainly piqued my interest.

BTW - Have a Honda 225 outboard on my current 25 ft fishing boat. It's a very good engine - 1500 hours plus, and no problems. Only thing is that they are maintenance intensive..

I agree 300hp is a bit optimistic. I was thinking... our boat originally came with Chrysler 318's (last owner put the Crusader gas hogs in). Not sure what the HP rating was on those, but guessing in the 180-200 range?? Going on that figure of 1/3-1/2, a couple 100hp motors would (at first guess) be capable of respectable cruising speeds. On that same first guess, I would think two 75's would at least get us the cruising speed we are at now. That is, *IF* that 1/3-1/2hp figure is accurate.

So much guessing.... would hate to purchase motors and find out it is not enough. Lots of research to be done.

The only way to make the electric drive work would be to have a diesel powered generator - too much energy for batteries alone...then you need to make sure everything is rated appropriately (duty cycle)...I'm positive you will find new diesels cheaper than a new diesel electric drive system.

You are likely to find the diesel conversion is NOT cost effective...if you want the range to increase your dollars will be better spent buying larger fuel tanks...or by slowing down...you can research david pascoe's articles to get a more comprehensive view from an objective, experienced individual...and the points made are still valid today.

If you really want the diesels, I'd suggest buying a used boat with a pair already installed...with the leap in fuel prices a few years ago, used boats are very cheap...a lot less hassle to buy it already configured.

Hybrid stuff is only good for those that have deep pockets at this time.-------Many of these hybrid cars will be worthless when folks learn what it takes to maintain them and what battery replacement costs.----Most new products are " great " when they are new !!-----Anybody know what happened to the GM product caled ---------" VOLT "

As far as more range, i'm afraid we're at our limit where we sit now. I know we could have our props worked over for a little more potential range, but that's about all we can do. We have gone through every nook and cranny in the boat trying to figure a good spot for additional fuel, but the largest tank we would be able to add is around 40 gallons. Not exactly worth the effort required.

As far as selling our boat and buying one already with diesels, that idea has occupied many conversations between my brother and I, but as you stated, the market is flooded with boats for sale... and CHEAP! That would be a good thing when it comes to by a new one, but is a very bad thing as far as selling ours. I would be surprised if we got $14k for ours. Brother wants to list it for $20k and see what happens, but.... I guess we'll see what happens.

racerone, If you're referring to the EV1, have you ever seen the documentary 'Who Killed the Electric Car'? The oil companies did. As for today's hybrids, batteries are so expensive because the manufacturers can charge that much. To anybody with some know-how, they can be rebuilt. Our Civics are just an array of NiMh "D" cells. As for maintenance on the rest of the car... cheaper than a gasoline Civic. Working for Honda, though, I can't speak for the other companies' hybrids.

Mark, I realize a diesel generator would be required. The batteries would essencially act as a buffer, or capacitor for the whole system. I think the size of the required generator would kill the whole project before any real planning starts anyway. We would need like 110+kW genny?!? I don't think we could fit anything NEAR that size in our boat.

Whether this becomes a reality or not, I'm still toying with the idea and would like to learn as much as I can about it.

I think you'll find you need a helluva lot more genset that 110KW...the 746 = 1 conversion is "pure" and doesn't account for any inefficiency...add to that the "surge requirement and things get real big...

On the other side of the coin, it is torque that is required to spin the propeller...that is why a "smaller" hp rated diesel can push the same hull at a given speed that a higher hp rated gasoline engine does..

factor in how the electric motor is rated too and I'm pretty sure you will find yet another factor.

you may want to consider replacing your current tank and maybe doing some rearranging of what is in the hull. you need to be mindful of the center of gravity, too....just food for thought.

Good discussion, folks.

Eric, maybe on another post I would like to hear how the oil companies killed the electric car. Doesn't make sense to me, given the historically high price of gasoline, it would seem that if current technology was a viable alternative, the market would switch to electric or hybrid cars pretty rapidly. However, every time I take a look, I find those vehicles entirely too limited in terms of range, power, utility, and expected longevity. My friends come to the same conclusion. Besides all of that, I am highly resentful that my tax dollars are going to subsidize something that the market is not realy to accept.

racerone said:

Anybody know what happened to the GM product caled ---------" VOLT "

Click to expand...

umm, they still make it and sales have increased steadily since it's introduction?
the all electric range has improved on the 2013 model with new battery chemistry?

I would go with about 80% of engine power for electric motor sizing.
I had a customer once that replaced a 230HP diesel engine in a Cat 330 excavator with a 200HP electric motor. The machine had more power with the electric motor.
The issue with electric motors is the inability to lug. A direct dive boat would have 1 speed unless you go with VFD motor$.

If one was going to put in a diesel generator set big enough to run propulsion motors, it would make more sense to just hook the diesel engine to the prop and forget about electric.

I think you're getting ahead of yourself.

The HP decision is determined by use.

I'm the inventor that put my CC 33' Sports Sedan on a tandem axle trailer and pull it with the Semi Pintle on my Dodge Cummins 2500...wide, tall and long. What are you using your boat for?

I plan to install twin Ford 4CYL hybrid motors from auto and use a marine exhaust manifold to "marine" the exhaust. Lots lighter and allows for many deep cell batteries low in the hull to keep my Chris Craft vertical - and on top. Why you ask...because I want to fish the mouth of the Columbia for Salmon and the thought of trolling without an engine running is fantastic. It doesn't take twin screws many revolutions - or horsepower - to keep it navigating true. Up and down river.

So: Figure out if you have a nitch like me, or you want a direct replacement for the weight and horsepower in your boat today.

Good luck - I will post again when I finish "Fortune Cookie" and provide photos.

Genset to battery to electric motor is less fuel efficient than direct engine to prop. While there are operational reasons for doing the whole genset to battery to electric motor, efficiency is not... unless you spend the majority of your time at idle/troll speeds and even that is dubious. For large scale systems it can make sense as it eliminates the need to a transmission to handle fwd/rev/idle. Also, internal combustion engines run best at a single constant speed and the whole genset thing allows this with speed control done electronically in the electric motors. Diesel electric trains work because there is no way to have a clutch survive startup from dead stop with direct diesel to wheels... Internal combustion engines have the max torque at some random speed about 80 to 90 % of WOT and zilch torque at low revs, while an electric motor has maximum torque output at zero rpms....