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Barry Rietz
Joined: 21 Jun 2006
Posts: 408
City/Region: Sierra Vista
State or Province: AZ
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thataway
Joined: 02 Nov 2003
Posts: 20443
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
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 Posted: Wed Mar 15, 2023 11:40 am Post subject: |
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This Mercury electric is much heavier than the Torqeedo 1103, has slightly more power, and seems to have the same performance as the Torqeedo. It costs more.
Merc: 60#, Torqeedo 30#! That alone is a deal breaker for someone who buys the electric motor for its light weight.
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Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
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rogerbum
Joined: 21 Nov 2004
Posts: 5910
City/Region: Kenmore
State or Province: WA
C-Dory Year: 2008
C-Dory Model: 255 Tomcat
Vessel Name: Meant to be
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| Posted: Wed Mar 15, 2023 2:45 pm Post subject: |
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| thataway wrote: | This Mercury electric is much heavier than the Torqeedo 1103, has slightly more power, and seems to have the same performance as the Torqeedo. It costs more.
Merc: 60#, Torqeedo 30#! That alone is a deal breaker for someone who buys the electric motor for its light weight. |
750W for the Mercury vs 520 for the Torqueedo means 1.44 times as much power which I think is a more than "slightly more power". The Torqueedo weighs 38.14 lbs. (17.3kg) with the battery and 24.9lbs(11.3kg) without it. The Mercury weighs 59.7lbs (27.1kg) with the battery and 43.0lbs (19.5kg) without. So Bob is correct in that there is a significant weight difference, it's just not quite as large as he quoted. The Torqueedo battery is 915WH in a 13.2lb (6kg) package while the Mercury battery is 1000WH in a 16.7lb (7.6kg) package. Thats 69.3WH/lb for the Torqueedo battery and only 59.9WH/lb for the Mercury battery. Both are well below the ~120WH/lb that is possible with Li ion batteries so I suspect that much of the weight is housing/water proofing and that energy densities will be much higher in larger, fixed battery systems. Given the similarity in battery capacity, range for the two motors will be similar if operated at similar power outputs.
For me, I see the main application of these engines is to and from shore in a tender and both have more than sufficient power and range for that. They are also potentially useful for the short picnic cruise. I personally don't see using these particular engines for fishing as I'm a "one more cast/fish" kind-of-guy and hence range matters a lot.
It will be interesting to see the evolution of electric engines in the larger horse power sizes and how that drives future boat design. It will also be interesting to see how it drives boating habits. High power electric engines can be very light weight but the energy density of gasoline is still about 50x higher than Li-ion batteries. However, electric engines are about 90% efficient while gasoline 20-40% efficient (so maybe a factor of 3 in efficiency). So.... if I want to replace the 150gal of fuel in my Tomcat with the equivalent amount of useful battery energy, I'd need (150g*6lb/gal)*50/3= about 15,000lbs of battery to get the same range/performance. Even if I save ~800# in engine weight, I'd still be looking at 14,000# of battery in a boat that can support maybe a few 1000# of weight. So bottom line, a EV boat isn't going to be useful for blasting out to and from the tuna grounds.
Similar calculations can be done for other applications - e.g. 20gal*6lb/gal*50/3 ~ 2000lbs of battery for the equivalent amount of usable energy. That might give me 100 miles of range at 6kts in a Tomcat or a 25 and for many, that might be enough to go near shore trolling for day. Of course, once we are into heavy fixed batteries not only does that require new boat design, it will require new trailer design to handle the increased load AND most importantly, new electrical wiring/monitoring at marinas. Many marinas already have 30A and 50A power at the docks but the days of a fixed fee to plug into power during a transient stay will go away once we get a few electric boats recharging at the marinas.
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