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I thought of that. You wouldn’t have the generator available for house needs like air conditioning or making pop-corn in the microwave with a DC generator. You could have something similar with a step-down transformer to 48VAC and a rectifier. Parts for this are not expensive. This would be a dirty and unregulated source of power however. There must be some electronics to control drive to the motor. It may not be happy with this kind of unregulated power supply. Other power converters may be prohibitively expensive.
Specs on the engine linked above are missing information. It doesn’t show maximum output or line regulation. It’s a 20kw Kubota, so one would think that max power output would be less than this. What happens if the drive system tries to consume more than the rated generator output? Does a breaker pop? That would be annoying, coming into a dock and give it a good goose of reverse thrust to stop the boat, Pop!
I think we’re starting to beat a dead-horse here.
RichIt’s not just the generator that must be properly sized, you have to convert the generator output to run the drive motor, probably 48VDC. I’ve been scratching my head over this and can’t think of a cost-effective way to do this at the power rating needed. I’m interested to hear how this operates on a long run like a few hours. If there is some magic there that converts the full 8KW generator output for drive to the motor, you’d have 11 hp. My guess is that you get much less than this, half that or less. Whomever sold this package must have provided specs on the drive system. What do they say about power output with just an AC generator driving it?
This is all very exciting. It would be great to replace the engine on my 424 with a diesel electric solution that generates household power for things like air-conditioning. In theory, we should be able to replace our transmissions with an AC generator and our V-Drives with an electric motor. I’m a bit dubious however since I haven’t seen such a solution that makes sense on paper for less than $100K.
I’m reluctant to call your baby ugly, but this doesn’t work out on paper. Before anyone else out there runs out and spends well north of 10K for an electric power-plant, do the math. There’s about 750W/hp. A 20kw electric motor provides 26hp to the shaft. It doesn’t lose any power for accessories, transmission, or V-drive so it may be equivalent to a 40hp engine. What is the performance of a 424 with a 40hp engine? I’d be surprised if it’s hull speed into wind and chop, but let’s say it is. That’s what you’d have if you have at least a 20kw generator to drive it and a charging system that can handle the load. Anything less, and you’re drawing from your batteries. You don’t list the size of your battery bank. I’m pretty sure your batteries aren’t big enough to help for more than a few minutes. Unless your charging system provides enough power to drive the electric motor all by itself, I don’t see how this works for more than getting in and our of your harbor.
If I’m wrong in my calculations, I’d be the first to apologize. Let us know how this performs on a passage.
Rich
I’m puzzled about these electric conversions. I suppose that it might work if your demands are very modest, say pulling in and out of your slip and maybe a bit of motoring to get out of the channel. The storage technology just isn’t there for cruising however. Let’s assume that you don’t care about powering into a headwind with chop for more than a few minutes. You’d like the ability to power in relatively calm seas and light winds for just 4 hours at only 5kts. An engine producing the equivalent of perhaps 15 hp would probably work. That’s about 11kw. With only batteries, you’d need about 1000 Amp hours at 12v. You can’t totally discharge your battery bank without damaging it. You could perhaps install 15 pairs of golf-cart batteries. I have no idea where you’d find the room, but let’s ignore that. The number of batteries doesn’t change if you change the voltage.
OK, so you want to put in a generator so you can extend your range. You’d need an 11kw generator and a charging system appropriate to your system. This only gets you minimal power. 5kw won’t do it. There’s some loss in the system so you’d probably need a 15kw generator.
It’s now 10 years later. Your needs have changed and you find that it’s time to sell your boat. For some odd reason, nobody wants to even look at your boat.
For long-distance cruising, the only way this makes sense is to put in a beefy 40kw diesel generator and an electric motor in place of the V-drive. I looked at that solution about 10 years ago when I repowered but there was no solution.
Torqeedo has something new on the market that has promise. The 40hp unit might work on the 424. I found a reference to price in the $100k range for the engine and battery bank.
https://www.torqeedo.com/us/en-us/products/inboardsRich
I installed Edson davits on my 424 when I first bought her 30 years ago. The davits bolted to the aft combing deck. From the photos, what you have appears similar. The deck area around the combing is quite strong, being cored with an inch or more of marine plywood. The lever arm presented by the davits is enormous however. While the davits could support 250lbs each, there is no way that the deck would support that kind of load. My dinghy weighed about 400 lbs empty, with about 250lbs on the end with the motor. The motor was a 30hp 2-stroke weighing about 135lbs. Though this was within the rated load for the davits, this proved unworkable. My dinghy was a 12’ 4” inflatable, so even if I took the motor off, really impractical, the thing only worked under motor. Any angle of heel would drag the bow or stern of the dinghy in the water. The arrangement would probably support a short dinghy with no motor.
I came up with a method of towing that worked. I pulled the lid off the motor and used a bridle to lift the engine and stern of the dinghy, leaving the bow dragging in the water. This reduced the load on the davits and distributed the load evenly between them. There was no longer an issue with the width of the dinghy either. The load on each davit was now about 75lbs. Though this worked, it still had issues because of shock loads transferred to the davits when running into a chop. I replaced the davits with custom made welded stainless. These have two legs on each davit to spread the load. They aren’t the prettiest things but they are functional and provide a great place for solar panels.
http://www.richardcarter.net/boat/davitSwimPlatform/
I’ve since replaced the dinghy and now have a 4-stroke motor. These new engines are much heavier than their predecessors, weighing in at almost 200 lbs. I still tow the thing by lifting only the motor end and leaving the bow in the water. I’d never take a chance transporting it this way in a severe chop such as Buzzard’s bay, but this works for me.
Rich
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The problem with the original tanks is a mistake made by the builder. The wood frame is fastened together with bronze staples. The heads of these contact the aluminum tank. Galvanic corrosion causes pinholes in the bottom of the tank where contact is made. If the tank has already been replaced once, I wouldn’t be concerned. If the tank is not leaking, you should keep an eye on it. You’ll see fuel accumulate under the engine and soak the diapers you put there if it leaks.
A leaky tank is not that big a deal but it’s a bit tedious to replace. You can pull the engine and push it forward on rollers to access the tank cradle. It’s a day’s work to pull it and another to put it back. Ask for details if you need to do this.Rich
My wife and I have attended several of these over the years and would really enjoy meeting up again. The last one was Point Judith RI. There was one in the Chesapeake that I missed, a bit far from Salem Sound MA. Mattapoisett is a beautiful destination and we’d love to meet up but I think our cruising plans take us down-east this summer. If our plans change however we’ll try to make it.
Rich
This should probably answer most questions you have about repowering.
http://www.richardcarter.net/repower/Briefly, if you plan to repower, you probably need to have the engine pan replaced. The geometry of replacement engines differ.
That looks like a nice job. I paid to have it done. A guy locked himself in the V-berth for a whole day with a grinder and roughed up the surfaces, then he laid in the glasswork. He had a fan in the deck hatch but I think he lost some brain-cells in the process. I think I paid about $1800 to have it done but that was 20 years ago.
They way you did it, it would be simple to lay-in some horizontal wood strips and make it neat. I’d suggest running a third set of stringers back a bit farther if anyone else does it. I had flexing all the way back to the next bulkhead. The port-side vanity bulkhead separated from the hull. You’d need more stringers to lay in the wood liner anyway.
I’ve been unable to upload the invoice as a pdf file so I uploaded again as jpg.
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We got the snot beat out of us on a Bermuda crossing about 20 years ago. The V-berth shelves and horizontal bunk panel separated from the hull from the pounding. As I’ve reported in earlier threads, separation started at the forward end of the V-berth shelves, much like a zipper. It then proceeded down the length of the shelves until they were separated from the hull. Without the shelf, oil-canning got worse and the v-berth itself separated. I think that if I had properly reinforced the attachment of the V-berth shelf to the forward bulkhead, I could have prevented the whole problem.
I had a glass-man do a repair in Bermuda. He added layers of 3/8 glass to the inside of the hull sections on both sides of the V-berth. These overlapped by about 3″, making the reinforcement 3/4″ thick where it overlapped. He added gelcoat to the repair to keep the odor down and make it look nice. I’ve had no problem since, but I’ve never experienced weather like that since then.
Rich
I’m not sure I understand your question but let me give it a try. I assume that the winch battery is up forward, placed there to avoid having to run a heavy set of cables to the winch. You should be able to charge them by simply connecting them to the house batteries. You should use a heavy gauge wire pair to connect this. 6 or 8 AWG is probably heavy enough. I chose to connect my winch directly to my house batteries but I had to use expensive wire, 2/0.
As for the house batteries, setting up a charging system for them is a pretty big topic. You’ll never get two boaters to agree on the right setup if there is such a thing. I suggest that you get a book and read up on it. Here’s a popular book that many folks like.
https://www.amazon.com/12-Volt-Doctors-Practical-Handbook/dp/187879700X
RichOne of my projects this past winter was to replace the 40 year old cockpit cushions that were original equipment with my 424. I can’t complain about the durability of the old cushions but they were surely at the end of their service life. I’ve looked for replacements on occasion over the past many years but the price was discouraging. I nursed the old cushions until they fell apart last summer. I did a web search for replacement cushions and found a reasonably priced vendor.
Today, I removed my boat cover and had a chance to see if the replacements would fit properly. I’m very pleased. The new cushions are thicker than those they replace. I think I could even sleep there though the seat is a bit narrow. I’ve attached a photo of them. Please ignore the dirt. I just pulled the cover off today. The vendor has my template and can make duplicate cushions for anyone interested. You might get a bit better price than me since they now have a template for the 424. I also attached my invoice.
If you’ve never had cockpit cushions, you should consider getting a set. They make the cockpit much more comfortable.On my 424, the deck around the hatches is plywood cored. There are stainless screws holding the hatches and it’s bedded with silicone sealant. Removing the old hatch takes about an hour.
Prop size selection is a function of the torque and speed of the engine that drives it and the gear reduction of the transmission and V-drive and of course the boat displacement and hull shape. Not all power plants work the same. I doubt that an electric motor would work well with the original prop. I suggest that you contact a propeller manufacturer and ask for their help.
