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My Future "Inboard" Conversion

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sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Initially Posted - 08/14/2012 : 07:36:46

These are awesome. I don't know how much they cost.

http://www.mastervolt.com/marine/products/podmaster/podmaster-21/#specifications

Seth
"Outlier" 1987 Catalina 25 SR/SK/Traditional Interior #5541
"Zoo" 1977 Morgan Out Island 30
"Nomad" 1980 Prindle 16
"Lost" 1988 Catalina Capri 14.2 (sold - yay!)
"Marine Tex 1" Unknown Origin POS 8' Fiberglass Dinghy
https://whichsailboat.com/2014/07/27/catalina-25-review/

Edited by - on

Sloop Smitten
Master Marine Consultant

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USA
1181 Posts

Response Posted - 08/14/2012 : 08:17:13

The smallest one, 2kW - 24V, is $5,299 at West Marine. That would be an awesome addition to a sailboat but probably not one that uses an outboard such as ours. Now if you had an inboard engine that needed replacing it would be a viable option from a replacement cost perspective. Also noticed it is designed for fresh water applications which I suspect means they don't recommend it for use in salt water.

Edited by - Sloop Smitten on 08/14/2012 08:19:38

Steve Milby
Past Commodore

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USA
5906 Posts

Response Posted - 08/14/2012 : 08:37:24

A friend installed an electric motor in his old wooden hulled full-keel sailboat, and he likes it, but says realistically it's only good for getting in and out of a marina. If he needs to travel a distance, he has an outboard motor that he can mount on it.

I recently saw a 30 hp Yanmar diesel engine for sale that was completely rebuilt by a well-respected shop in Annapolis, for $5500. For a little more than the electric motor, I'd much rather have a reliable diesel engine that could take me wherever I wanted to go. A smaller engine would cost considerably less, of course.

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 08/14/2012 : 11:50:55

I wonder if the passively spinning prop, i.e. when not being used to propel the boat, could provide sufficient power to recharge the batteries?

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 08/14/2012 : 17:34:15

You'll need a lot of batteries and serious wires for 2 KW - 83 amps at 24V at full throttle, 166A at 12V. Running it from a DC generator adds the inefficiency of the generator and voltage regulation; an alternator is more efficient, but then you have more loss converting it to DC. I'll just connect the 70% efficient gas engine to the prop and skip the intermediate electricity, but it would be sweet if it was practical. I did think about mounting the power unit of my trolling motor to the bottom of my last boat. A permanent magnet motor can operate as a generator, but it isn't very efficient with the small prop.

Edited by - on

Dustysailz
1st Mate

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USA
85 Posts

Response Posted - 08/14/2012 : 17:45:09

In a recent issue of Sail magazine, a supplier was advertising pods that were very similar to these, however, they were strictly for use when docking and as an alternative to bow thrust ers and some which were used on the stern.

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dmpilc
Master Marine Consultant

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USA
4593 Posts

Response Posted - 08/14/2012 : 19:09:43

Based on another member's reports, the Torqueedo outboard may be a better option. I do like the pod approach, however. submerged, out of the way, quiet, and two 12 volt deep cycle batteries could be mounted in the gas locker very easily.

Edited by - on

putzmeister
Navigator

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100 Posts

Response Posted - 08/14/2012 : 20:50:14

http://s425.photobucket.com/albums/pp337/jehutchisonjr/1932%20Herreshoff%20FI%2023%20Crusader%20restoration/?action=view&current=IMG_1469.jpg

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Steve Milby
Past Commodore

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USA
5906 Posts

Response Posted - 08/15/2012 : 04:46:04

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by putzmeister
 http://s425.photobucket.com/albums/pp337/jehutchisonjr/1932%20Herreshoff%20FI%2023%20Crusader%20restoration/?action=view¤t=IMG_1469.jpg

<hr height="1" noshade id="quote"></blockquote id="quote">
What a spectacular restoration!

Edited by - on

putzmeister
Navigator

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100 Posts

Response Posted - 08/15/2012 : 07:34:46

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Steve Milby
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by putzmeister
 http://s425.photobucket.com/albums/pp337/jehutchisonjr/1932%20Herreshoff%20FI%2023%20Crusader%20restoration/?action=view¤t=IMG_1469.jpg

<hr height="1" noshade id="quote"></blockquote id="quote">
What a spectacular restoration!
<hr height="1" noshade id="quote"></blockquote id="quote">

Yeah! and it's on our lake too!

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 08/15/2012 : 18:17:16

One horsepower is about 750 watts, 0.75 KW, but that doesn't work very well in comparing gas/diesel to electric motors. A 9.9 would be 7.4 KW! Horsepower is a function of torque x rpm. Gas engines develop decent torque at high rpm to get high HP; diesels develop high torque at modest rpm which makes their HP rating deceptively low for their pulling power; electric motors develop maximum torque at stall, zero rpm, so they have zero horsepower at maximum torque. Increasing the load increases current draw, torque and efficiency to a point. The Torqueedo throws out the legacy ideas based on gas engines and optimizes their system for the characteristics of an electric motor.

Edited by - on

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 08/20/2012 : 17:24:26

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dmpilc
 Based on another member's reports, the Torqueedo outboard may be a better option. I do like the pod approach, however. submerged, out of the way, quiet, and two 12 volt deep cycle batteries could be mounted in the gas locker very easily.
<hr height="1" noshade id="quote"></blockquote id="quote">

David, those are precisely the reasons why I like this. Plus this would satisfy my inboard envy. On my inland lake, the range on this thing would satisfy my needs and we have very little currents.

Plus this is something I could install myself while I have serious doubts about my ability to complete a conversion to a diesel inboard (limited experience with fiberglass construction), even a sail drive.

The price is still high compared to my budget, however. I wonder if I might rig something up myself for much less.

I also wonder about the possibility of an accident or some other failure shorting the thing to ground, creating an electric shock drowning risk.

Edited by - sethp001 on 08/20/2012 17:24:42

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 08/20/2012 : 17:56:39

This could be easily adapted to a permanent mount on the bottom. 24v and 100 lb thrust: http://www.basspro.com/Minn-Kota-Engine-Mount-Freshwater-Trolling-Motors/product/73581/118689#chart It would work in moderate conditions and short range with regular recharge access for about $1000.

Edited by - on

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 06/10/2013 : 20:26:15

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave5041
 This could be easily adapted to a permanent mount on the bottom. 24v and 100 lb thrust: http://www.basspro.com/Minn-Kota-Engine-Mount-Freshwater-Trolling-Motors/product/73581/118689#chart It would work in moderate conditions and short range with regular recharge access for about $1000.
<hr height="1" noshade id="quote"></blockquote id="quote">

I've been rolling Dave's idea around for several months now. Considering that I'm on a relatively small inland lake and after learning from some research, I believe this idea has great merit.

Amongst other sources, I've found this: http://www.trollingmotors.net/engine-mount-trolling-motor-guide, which leads me to believe if I bought this motor http://www.walmart.com/ip/15686827?wmlspartner=wlpa& adid=22222222227000000000& wl0=& wl1=g& wl2=& wl3=21486607510& wl4=& wl5=pla& veh=sem, I might do okay on my inland lake with negligible waves and current.

In the course of reading, I've stumbled into a lot of material about propeller selection. This leads me to wonder: if I choose to buy this motor and mount it to the bottom of the boat, do you think I would do well with the propellers supplied, or if I would do better with a three or four blade prop. I am yet to be able to figure this out.

Edited by - on

GaryB
Master Marine Consultant

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USA
4311 Posts

Response Posted - 06/10/2013 : 20:53:44

This model will allow you to have the best of both worlds. Electric or diesel power.
http://www.mastervolt.com/marine/products/hybridmaster-ultra/hybridmaster-10-ultra/

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 06/11/2013 : 11:48:25

I think 160 # of thrust is more than adequate. I pushed my CM-21 with 40 #, but that was right at the limit and would stay at 100 minimum for the C-25.

Edited by - on

panhead1948
Captain

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345 Posts

Response Posted - 06/11/2013 : 13:21:12

Several years ago I was at the Chicago sailboat show. Com Pac had an 18ft Cat boat with electric power. The unit looked like the bottom of a trolling motor and bolted to the keel. While sailing the spinning prop will charge the batteries. The motor had two stainless steel studs that held it in place. The wires came up through one of the studs. On the C25 I think the motor could be bolted the the sked in front of the rudder.

Edited by - on

sethp001
Mainsheet C-25 Tech Editor

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814 Posts

Response Posted - 06/16/2013 : 08:23:10

Any thoughts on how much drag this thing would induce? I won't get any PHRF rating change but I wonder how much it will slow the boat down in light air.

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