Walking a Twin Engine 40 footer Sideways without a Thruster

Discussion in 'Sport Yachts/Yachts' started by jmunro123, Oct 10, 2010.

  1. jmunro123

    jmunro123 Member

    Feb 2, 2008
    Gran Bend, Great Lakes
    2004 Sea Ray 390 Motor Yacht
    We do not have a Thruster and I want to learn to 'walk' the boat sidways by using the engines and rudders. I practised at the dock yesterday for about an hour and could not get it to go.

    Can someone share how to make this work?
  2. Jacob

    Jacob New Member

    Sep 30, 2007
    Vancouver Island
    1998 Bayliner 4788 (sold).
    1999 Sea Ray 480 DB (sold)
    2005 Grady-White Marlin 300
    Yamaha F250's
    While every boat is different, I have found the following to work under light conditions (i.e. not much wind or current), for twin screw inboard boats only.

    If you want to crab the boat to a dock on the starboard, "cock" the engines with port gear ahead, starboard gear reverse, and the helm hard over to port. This works because to bow is brought around (in a clockwise spin) by the opposing propellors, but the stern is pushed to starboard by the port propellor discharge current hitting the rudder which is hard over to port. The starboard propellor discharge current is in reverse and this has no effect on the rudder. Of course, this is only true on an inboard configuration.

    You may have to throttle up a bit more on port than starboard, and tunnel hulls can throw the effect off a bit. The opposite works for crabbing the boat to port.

    There are other methods for walking the boat over, space permitting. You approach the dock (on starboard) going forward on an angle with the bow in. When the bow has almost reached the dock, engage port reverse, perhaps throttling up a little. Starboard should be in neutral. When the boat stops moving, go ahead on starboard momentarily and port reverse. The boat should be at the dock by now.

    If this doesn't work then revert to profanity and vigourous arm waving. Gears should be in neutral. Take time to order a thruster.

    Hope this helps, Jacob
  3. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    Walking a boat sideways more than a boat width is easier when you have large asymetrical thrust found on boats with big props, lots of pitch and plenty of torque coupled with a large centerline to centerline distance between the shafts. To put this in Sea Ray terms, It works well on 50 -60 ft boats, on boats with a COG about in the middle of the length of the boat...sedan bridges, is somewhat more difficult on the mid-40 ft boats and is almost impossible to do on under 40 ft boats. The smaller boat will eventually go sideways, but not without a lot of jockying the gears and throttles, and usually not without moving ±1/2 a boat length forward or astern.
  4. fc3

    fc3 Well-Known Member TECHNICAL Contributor

    Nov 12, 2006
    Northern NJ
    1999 Sea Ray 330DA
    Twin 7.4 MPI (310 propshaft HP) V-drives
    Twin Mercury Marine marinized 7.4L L-29 V8s
    Cast iron block w 4-bolt mains
    4.25x4.00 bore & stroke
    What Frank said, nearly impossible with under 40' Sea Rays. If the conditions are right, I can do it, but so far, I've only done it successfully a handful of times. Not enough rudder authority.
  5. FireIsland1

    FireIsland1 New Member

    Apr 22, 2009
    long island
    I can crab my 37 if I work the throttles
  6. AnchorsAweigh

    AnchorsAweigh New Member

    Jun 27, 2010
    Kenora, Ontario
    1977 - 300 Weekender
    Twin 5.7L Mercruiser Inboards
    I crab my 30 footer all the time with ease. I center the wheel/rudders and use shifters only, no throttles. Planning ahead and patience is the key.
  7. CSR_Admin

    CSR_Admin Administrator Staff Member

    Mar 10, 2004
    I was just eating breakfast reading CSR, saw this thread, and thought to myself "I wonder what people's expectations of walking a boat sideways really are". You can see above 2 experience posters and boaters added the caveat "when conditions are right". This basically means, no wind, no current, and plenty of time. Walking a boat sideways is when the boat is always parallel to the dock. Not where the bow and stern get closer one end at a time. Its really only useful as a last resort if you plan your docking accordingly and find your self a few feet away from the dock stuffed in between two boats. Why is it not useful otherwise? Because it would take far too long. The only time I ever use the technique is actually to get the boat away from the dock as I don't usually screw up on the way in. Of course there are those that think they can walk their twin screw boat sideways at 2 knots without a thruster. You guys please skip over this post. To everybody else with aspirations of doing this, its not going to happen. There are much more effective ways of moving a boat into a slip or T-Head.

    Bow thrusters. Any salty skipper would never use one on a twin screw boat pulling into a slip but there is a lot to be said for them when parallel docking on a T-Head and doing to right. This is an effective way of moving a boat sideways. There is an art to putting one engine in forward, one in reverse, adjusting the throttle on one or both, then using the thruster to get the boat moving exactly sideways while only using thruster inputs until almost touching the dock and everything going back to neutral. The art of great docking is like chess, as few moves as possible. For example, pulling into a slip can be reduced to idling up to it, putting one engine in reverse with some throttle to get the stern moving around and into the slip, then bring the other engine to reverse to back straight into the slip, then bumping both in forward to stop. Three inputs, done. A T-Head you head into it at 45 degrees, coast into it in neutral, pull the outboard engine into reverse, neutral, tie up. 2 inputs or 3 inputs depending on how you look at it. Trying to walk a boat sideways without a thruster requires a constant parade of inputs for very little movement, which is why a good captain will only whip out that trick to make up for something not done right prior.

    Was supposed to be a short post, sorry. I could talk about boat handling around docks for days.
  8. Tonka Boater

    Tonka Boater Active Member GOLD Sponsor

    Jun 11, 2008
    Wayzata, MN
    1997 232 BR
    502 MAG, Bravo I
    Excellent little essay. I never thought of docking being like chess but it's a perfect analogy. Twin screw, single screw, inboard, outboard, thruster or not....you are correct the goal is to use as few moves as possible. Master all of your moves so you can use the appropriate one at the appropriate time with an infinite variable of conditions.
  9. jmunro123

    jmunro123 Member

    Feb 2, 2008
    Gran Bend, Great Lakes
    2004 Sea Ray 390 Motor Yacht

    Thanks for clarifying the expectation of this move. I don't have a thruster so that is out. I would like to get one, but hey for $10,000 to $12,000 I can repair a fair amount of gelcoat. In three years of bigger boating I have not hit anything I am very careful but look at this manouver more as an advancement of my skills and a good tool to master just incase.

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