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Old 08-25-2018, 08:08 PM   #21
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City: Ashland, MA
Vessel Model: 1990 Silverton 40 aftcabin
Join Date: Jul 2016
Posts: 1,208
I run on one engine most of the time after getting used to 5K travel in our old sailboat. I swap engines on the return. Operate the running engine around 1750-1800 RPM which moves our boat at about 6-7K depending on conditions. Our auto pilot makes steering a breeze.

Docking, dangerous channels and so forth demand running both engines. Sure, the $ saved is not spectacular but I learned to be very conservative when I didn’t have any $.
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Old 08-26-2018, 03:23 AM   #22
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City: Edgewater, MD
Vessel Name: Catalina Jack
Vessel Model: Defever 44
Join Date: Nov 2011
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Quote:
Originally Posted by djmarchand View Post
Why do you want to run a twin on one engine? To save fuel? Maybe but not much. The only objective analysis of this possibility Ihave seen was done by Bob Lowe, a former boat yard owner, and compared fuel economy with one vs two engines for two boats, a Grand Banks Alaskan 45 and an Ocean Alexander 50. The difference in fuel economy was negligible. See the attached pdf graph.

You can run on one engine without locking the prop on a Velvet Drive transmission. Bob Lowe's detailed comparison of freewheeling vs locking the prop on the dead engine didn't show any conclusive advantage to either method.

One downside is that you may be overloading the single engine. The only advantage in addition to a little fuel economy is less maintenance on one engine vs two running all of the time.

All in all, I wouldn't do it.

David
Here's my recent experience. While up-locking the eight stair step locks in Ottawa the Drivesaver saver coupling on the port side fractured thus parting the shaft from the BW transmission. We had to drive 18 miles on the Rideau Canal on one engine to reach a repair marina. At 1,300 RPM we achieved slightly more than 5MPH. It seems to me that this would have consumed noticeably less fuel than running on both engines. Our boat is a Defever 44 and weighs 56,000 lbs with water and fuel tanks full which they were at the time.

I don't run on one engine. It's annoying trying to control the boat even though the rudders on a Defever are comparatively larger. Glendinnings are your friend.
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