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Old 08-25-2018, 07:47 AM   #1
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Boat handing on one engine

Advise on using our twin screw 36 SeaRay aft cabin with one engine
Boat handling advise
We have Borg Warren velvet Drive transmission
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Old 08-25-2018, 07:59 AM   #2
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A little more difficult to steer, you will not be able to go as fast. Otherwise, not a problem. You will not hurt anything.
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Old 08-25-2018, 08:01 AM   #3
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A little more difficult to steer, you will not be able to go as fast. Otherwise, not a problem. You will not hurt anything.


Leave inoperable Drive in neutral??
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Old 08-25-2018, 08:04 AM   #4
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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
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Old 08-25-2018, 08:08 AM   #5
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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 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


We have a failed starboard engine but would still like to take the the boat out on just the port engine
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Old 08-25-2018, 08:26 AM   #6
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Sounds like you're planning on continuing to enjoy your boat while sorting out an issue with one of your engines. If so, I would remove the prop from the engine that's down. As far as handling, you'll be fine in open waters. The challenge is putting the boat back in the slip as most twins have small rudders. But you can practice and get a feel for it and then determine if it's doable. Hope it works out. Good luck.
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Old 08-25-2018, 08:35 AM   #7
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With our twins, docking on one engine is easier in one direction or other... depending on which engine we're using, associated prop walk, and which side of the boat it is that we're trying to turn into.

We approach our 4-way slip to port, and I can get the boat in there stern-to if the starboard engine is running. If our slip were to our starboard, I could get in there stern-to with the port engine running. In each case, it's very similar to a singles-screw boat with prop walk in the (whichever) direction... although not as well balanced, and with smaller rudders.

Otherwise, takes extra juggling, at least one crew with a spring line.

Or docking bow-in (but our finger piers aren't long enough for that).

Or docking elsewhere altogether.

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Old 08-25-2018, 08:59 AM   #8
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If you go slow it will work fine. People try to go too fast and that steers the boat and overloads the engine. If you go 5 kts or so steering will be OK. Then you can experiment. Turning toward the dead engine will be easier than the other way. Removing the prop will help by reducing drag in that direction.
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Old 08-25-2018, 09:01 AM   #9
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Lock the shaft and boat on one engine.

Other than being a handful to manuever on one...enjoy your boat.

Can't imagine there's insurance ramifications, may want to check.
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Old 08-25-2018, 09:45 AM   #10
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Now that I see what you are doing, I agree it will be fine. If you can remove it easily, then removing the prop on the dead engine is a good idea. It will remove some drag and result in a little less helm to counteract. It will also make docking easier.


If you keep the speed down, say 6 kts or less, then you should be fine with a bit of extra load on one engine.


David
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Old 08-25-2018, 10:06 AM   #11
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Sounds like you're planning on continuing to enjoy your boat while sorting out an issue with one of your engines. If so, I would remove the prop from the engine that's down. As far as handling, you'll be fine in open waters. The challenge is putting the boat back in the slip as most twins have small rudders. But you can practice and get a feel for it and then determine if it's doable. Hope it works out. Good luck.


We will be trying this today
Thank you so much
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Old 08-25-2018, 10:24 AM   #12
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If you never pilot a single screw and never docked with your boat on a single engine I would recommend you to practice away from your dock so you know how your boat reacts on one screw in forward and reverse. Handling is quite different. 1 month ago a guy came to dock at my marina with one engine down, apparently he was not aware of prop wash effect and not used to dock on 1 engine, he spent more than 1h trying to get into the slip in reverse.

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Old 08-25-2018, 10:34 AM   #13
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I had boats similar to yours in the past, and I wouldn't want to be maneuvering on one engine unless I had practiced beforehand. Low draft, sail affect, and small rudders are not a good combo with one engine. Just my .02.
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Old 08-25-2018, 10:58 AM   #14
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Tunnels on that Sea Ray?

Tunnels and small rudders can be the bane of single engine docking.
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Old 08-25-2018, 11:26 AM   #15
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One other consideration is your shaft logs. Too often the drip less installers cross connect the water feed from both engines without isolators. A sister ship of ours hydro locked his non running engine because of this.
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Old 08-25-2018, 11:52 AM   #16
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Steering towards the live engine side at any speed will be an issue. If there is traffic, I'd consider flying the Delta flag.
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Old 08-25-2018, 01:44 PM   #17
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CG, we just took our 550 Sedan Bridge about 90 miles down the Columbia on one engine to get the port transmission repaired. We left the marina at The Dalles, OR, went through Bonneville Dam then docked at Portland's Columbia River Yacht Club. The next day we left the YC, went about 5 miles further downriver then a couple of miles up the Willamette River then down the Multnomah Slough.


The boat ran well, cruising at about 8 kts through the water plus a 2kt push from the current. Much of the trip was done in 5'-6' waves with a couple of areas where they got a bit larger.


Running at that speed on one engine, I ran about 1100 rpm's. With both engines, to run at that speed would be about 1000 rpm's, so not a huge difference.




There were only a couple of scary moments but those were minimized by using the bow thruster.
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Old 08-25-2018, 03:01 PM   #18
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I was out with a friend 2 weeks ago on his 33 Searay express doing a test run. One engine quit so we had to go back to his marina on one engine.
He also has the prop pockets. He had one heck of a time trying to keep the boat straight. Wasn't his first time at it either. Rudder hard over was not enough to overcome the boats tendancy to go to one side.
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Old 08-25-2018, 05:21 PM   #19
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Good luck with those prop pockets. Pita!!!!
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Old 08-25-2018, 07:22 PM   #20
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Quote:
Originally Posted by ChesapeakeGem View Post
We have a failed starboard engine but would still like to take the the boat out on just the port engine
I had a failure on Port in June a few years ago. I had the repairs done in the fall. I spent the whole summer cruising on one engine.
I quickly learned where the boat wouldn't go, so didn't go there.
Docking often requires use of reverse gear. Learn the prop walk and use it to your advantage. On most (all?) twin engine boats, the prop walk is towards the centreline of the boat, so when using only Stb, the stern will move to Port and vice-versa. Use that to your advantage when turning, and when docking and you will be fine. You can NOT fight it, so try very hard to avoid needing to move the stern to Stb.
Everything else must be done at slower speeds than when you had 2 operating engines.
With Velvet Drives, no need to be concerned about the non-operating side.
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