Wooden boat has a write up on an electric boat repower sept/oct 2013 - SailNet Community

   Search Sailnet:

 forums  store  

Quick Menu
Boat Reviews  
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Hatches and Portlights
Interior And Galley
Marine Electronics
Other Items
Plumbing and Pumps
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here

Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
Old 08-20-2013
davidpm's Avatar
Senior Member
Join Date: Oct 2007
Location: Madison
Posts: 3,837
Thanks: 207
Thanked 52 Times in 44 Posts
Rep Power: 8
davidpm is on a distinguished road
Wooden boat has a write up on an electric boat repower sept/oct 2013

I’ve been very interested in electric powered yachts for some years.
They sound great in just about every way. They are known for being quiet having full torque at low rpm etc.

The big problem of course is range. One guy summed it up well. He said that when he left the dock he had the equivalent of ĺ of a gallon of gas with him.

Solar, wind, Honda generators do not generate sufficient amps for long enough to solve the range problem. The real solution of course is a diesel generator. This seems a little silly of course because of you are going to put in a diesel anyway you might just as well have it drive the propeller directly.

Big catamarians are an exception of course. You can replace two diesel engines plus a genset with a larger genset and actually maybe even save some money and maintenance and give the owners lots of power for toys.

The following are the specifics and some of my comments on the repowering of Vagabond, a 1909 wooden launch that originally had a 30 HP engine that was replaced with a 40 HP engine in 1923.

The system they installed included:
  • Elco 35Kw (equivalent to 70-hp) electric motor
  • 6-kW Kohler 1,800 rpm diesel generator
  • 8 Odysssey PC1800 batteries (214 amp-hour)
  • Charger that would work from shore power or genset putting out 25 amps at 110 volts
During sea trials they found that:
At 600 rpm they would go 4.4 knots and the generator could keep up and not drain the batteries. They had a 12 gallon tank and only used 0.3 gallons per hour. So they had a range with diesel of about 48 hours with a 20% fuel reserve at 600 rpm.

They can do near hull speed on batteries alone but the range would then be only 3 hours the generator can not keep up the the battery drain at that speed.
They figure they have a range of maybe 5 hours at 4.4 knots under battery alone.
Obviously a larger generator would change things but they selected the 6kw unit because it fit well in the boat.

My observations are the following.
The weight ended up being very close even with the batteries. (They decided not to go lithium due to cost and risk)
The cost if you are considering a genset anyway is probably still higher but maybe not that much higher.
I’m thinking that placement and sound control of a genset may be better than a diesel primary motor.

The thing that really struck me was the 0.3 gallons cost to run the genset. I’m guessing that pushing that boat at 4.4 knots would take any regular engine about a gallon an hour.
For someone at a dock using only a tank per year this wouldn't save much. But someone going from NYC to Miami and back it could be huge.

So the with .7 gallons per hour running the genset saved plus even more saved when plugged into the dock plus quiet motoring for 3-5 hours at a time. Super control at low speeds this might not be as stupid an idea as it sounds at first.

And as a freebe you get almost unlimited power for either 110v or 12v toys.

Obviously if you only plan on replacing your current shaft anchor with a new diesel and have no ambitions of putting in a genset this idea is going to cost a lot more. But if you are thinking of a genset anyway a slightly bigger genset plus electric drive motor and some batteries might still be more expensive but would come with some significant advantages including the maintenance of only one diesel.

It is certainly a premium solution but very interesting.
I'm figuring 16k for the motor (I have no idea why this motor is so expensive), 7k for the genset, 6k for batteries and maybe 2k for charger, I'm just guessing.
Lots of expensive switches and wire and labor too.
Over 31k in parts

I'm also aware that the engineering is not trivial. This guy had some of the best people in the planet work it out for him. To get the most from an electric drive you need to swing a big prop for example and modifying some boats to use a bigger prop may be expensive or impossible.
The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.

Last edited by davidpm; 08-20-2013 at 11:46 PM.
Reply With Quote Quick reply to this message Share with Facebook

Quick Reply

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Wooden Boat, What does it take to maintain one? jephotog General Discussion (sailing related) 21 11-29-2010 04:03 PM
NewEngland crew (2) seek boat in late Sept BoatlessBoston Crew Wanted/Available 3 09-02-2010 07:13 AM
Free Boat? Wooden, hmm, Just come get it? hmm.. Valdensule Boat Review and Purchase Forum 10 06-26-2009 10:12 AM
Buying a boat that needs a repower - nuts??? blowinstink Boat Review and Purchase Forum 6 06-14-2009 09:21 PM
Wooden Kit Boat Cruisingdad General Discussion (sailing related) 20 10-11-2007 09:34 AM

All times are GMT -4. The time now is 12:30 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2015, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.