Docking I/O vs. IB

[RollerCoastr]

Yes, all counter-rotating, angled-shaft twin I/B's will behave that way to some degree.

To clarify, when I said my boat doesn't like to walk, I was referring to moving the entire boat on the X axis without a thruster.

 

[320Bob]

Everyone understands that when a single prop rotates, it pushes the boat forward and also walks the stern in the direction of the prop rotation? Imagine your prop is a tire and your boat is on pavement. When the tire turns the stern goes in the direction that the tire turns. That's what happens when you engage the transmission of a single propped boat. The stern walks in the direction of the prop rotation. If you use one lever the stern goes to port. If you use the other lever the stern goes to starboard. I wonder how strong that effect is on, say a 340SD. It is pretty strong an a diesel 36 DB.

JVII,
I thought you posted a while ago your 330 had Axxius. If that is true doesn't that help with docking maneuvers compared with a stern drive boat without that system?

 

[JV II]

JVII,
I thought you posted a while ago your 330 had Axxius. If that is true doesn't that help with docking maneuvers compared with a stern drive boat without that system?

That wasn't me. Axius is something else. A child can dock a boat with Axius and no practice. I don't know if I'd want the complexity and additional parts of Axius. I know I don't "need" it. I do know that a stern drive boat with a bow thruster is a completely different animal than a stern drive boat without one. People are amazed at what I can make the boat do at the dock.

 

[Kameroo]

I've driven the Axius, and would buy it in a second if I could afford or justify it. Since I'm still saving for the little ones to go to college, I'll keep on learning with my inboards.

Anybody else notice a lack of humility in some of these posts? We were all new once and had to learn. I still try to learn something almost everytime I dock. Sometimes this time of year, I'm out of practice and get spanked for not being aggressive enough in the wind.

 

[pKai]

Bow thrusters are for weenies. (present company excluded of course.)

:smt043

+1! And to this I will add that Axius, Zeus, or any other kind of "pod" drives are for weenies with way too much money -- Unless your boat's name begins with "USS" or "HMS", its not big enough to need any of these.

I have both a twin sterndrive (Four Winns 245 Vista) and a twin inboard (1990 SR 310EC, actually 33' and not "V")..... The inboards are much easier to maneuver in spite of the loss of vector thrust. With the SeaRay, I can dock easily in places that are more difficult with the sterndrive Four Winns. I've also driven a 310 Dancer of the same vintage as my EC -- same hull mold, but has "V" drives instead. I can tell you that shifting two big blocks ~4 feet aft (my engines are under the helm seat) makes a HUGE difference in how the boat handles. Nothing beats "true" inboards for balance and handling characteristics (apologies to all you "V" drive owners...)

Ignore people that tell you not to use the rudder in an inboard -- unless its so small to be useless. The technique described earlier of cranking the rudder away from the dock, shifting the far engine to forward and the close to reverse works like a charm -- been using it for years. The engine in forward pushes water against the rudder making your aft want to move towards the dock and the boat want to rotate. The other engine (in reverse) has no effect on the rudder and counteracts the tendency to rotate -- net result if you fiddle the RPMs right: your boat goes sideways. Fiddling the RPMs right takes a bit of practice and of course varies from boat to boat, but its very worthwhile to learn. Once you get it, you'll be able to "walk" your twin inboard sideways like a pro.....

 

[Gofirstclass]

I'm a firm believer in the advantages of IB's vs I/O's when docking. One IB advantage that I have not seen anyone mention is the point around which your boat will pivot is in a different location. When I use the term pivot point I'm referring to the movement of the boat when one shifter is forward and the other in reverse.

With I/O's, because they hang off the transom, the pivot point is usually right at the transom. With IB's, because the props are several feet ahead of the transom, the pivot point is several feet further forward.

To see what a difference this would make picture holding a pencil in the middle of its length and spinning it around in a circle. The diameter of the circle is the length of the pencil. That would be close to the equivalent of having IB's. Now grab the pencil by the eraser and spin it in a circle. The diameter of the circle becomes twice the length of the pencil. This would be like having I/O's.

Obviously the advantage of IB's is that the boat can be spun in a much smaller circle.

When I bought my 330 in 2002 my docking maneuvers were not a bit pretty. It's a good thing the corners of my dock were well padded. The solution was to practice making approaches in all kinds of winds and before long I was able to make a "no touch landing".

I'm in the process of buying a 550 Sedan Bridge. I am going to have a bow thruster installed because we live in a high wind area and also will be boating in Canadian waters where currents could be a problem. Call me a Weenie if you want, I can handle it much easier than I can writing checks to repair boat damage.

 

[Alex F]

I'm a firm believer in the advantages of IB's vs I/O's when docking. One IB advantage that I have not seen anyone mention is the point around which your boat will pivot is in a different location. When I use the term pivot point I'm referring to the movement of the boat when one shifter is forward and the other in reverse.

With I/O's, because they hang off the transom, the pivot point is usually right at the transom. With IB's, because the props are several feet ahead of the transom, the pivot point is several feet further forward.

To see what a difference this would make picture holding a pencil in the middle of its length and spinning it around in a circle. The diameter of the circle is the length of the pencil. That would be close to the equivalent of having IB's. Now grab the pencil by the eraser and spin it in a circle. The diameter of the circle becomes twice the length of the pencil. This would be like having I/O's.

Obviously the advantage of IB's is that the boat can be spun in a much smaller circle.

I think this is pretty good explaination, which also mean that to move the bow in I/O boat you need a lot more torque when you have side wind. This I'd say another disadvantage.

When I bought my 330 in 2002 my docking maneuvers were not a bit pretty. It's a good thing the corners of my dock were well padded. The solution was to practice making approaches in all kinds of winds and before long I was able to make a "no touch landing".

When we upgraded to 320DA we had to be moved to a different side in the same marina. We get the side wind now 95% of the time, so "no touch landing" is no longer common for me, unless it's light wind (15mph or less). Since I always have the full camper on my boat moves different than those without camper. The camper is like a sail when the wind blows so becides controlling the bow my stern moves sideways as well, which I have to account for. When I did the "touch landing" for the first time on 320 I asked experience folks and they said that what the pilings are here for, it's called "soft landing". With side mild or strong wind there's no other way to dock, even thrusters may not fix it 100%. From that point on I felt very comfotable and can dock her in the strong wind as well. So far the strongest was 35MPH. I hope I don't have to bit this record.

 

[JV II]

Ignore people that tell you not to use the rudder in an inboard -- unless its so small to be useless. The technique described earlier of cranking the rudder away from the dock, shifting the far engine to forward and the close to reverse works like a charm -- been using it for years. The engine in forward pushes water against the rudder making your aft want to move towards the dock and the boat want to rotate. The other engine (in reverse) has no effect on the rudder and counteracts the tendency to rotate -- net result if you fiddle the RPMs right: your boat goes sideways. Fiddling the RPMs right takes a bit of practice and of course varies from boat to boat, but its very worthwhile to learn. Once you get it, you'll be able to "walk" your twin inboard sideways like a pro.....

That's what I'm looking for. With twin engines you can make the boat dance in ways that seem impossible. It doesn't just go fore and aft. Even with a single engine, you can do some impressive things. Its a matter of analysis and trial. I hope this string gives someone some ideas to try.

 

[HUMPH]

I think this is pretty good explaination, which also mean that to move the bow in I/O boat you need a lot more torque when you have side wind. This I'd say another disadvantage.



When we upgraded to 320DA we had to be moved to a different side in the same marina. We get the side wind now 95% of the time, so "no touch landing" is no longer common for me, unless it's light wind (15mph or less). Since I always have the full camper on my boat moves different than those without camper. The camper is like a sail when the wind blows so becides controlling the bow my stern moves sideways as well, which I have to account for. When I did the "touch landing" for the first time on 320 I asked experience folks and they said that what the pilings are here for, it's called "soft landing". With side mild or strong wind there's no other way to dock, even thrusters may not fix it 100%. From that point on I felt very comfotable and can dock her in the strong wind as well. So far the strongest was 35MPH. I hope I don't have to bit this record.

Roll up the sides before docking when it's real windy....worth the trouble!

 

[Gofirstclass]

Depending on the direction the wind is coming from, most of the time you can probably back into the wind and let it help guide your boat into the slip.

In cases where the wind is coming from off your bow you may not be able to do that. In my old marina if the wind was anywhere out of the north (NW, N, NE) I had to point the bow into the wind and back the boat down the fairway. I would start at the upwind side of the fairway and back down from the wind. When I got to my slip I would try to line up and make the first approach the only one I had to do.

It was tricky because there was only 50' between the finger docks and my boat is just shy of 36'. The boat has an 11'5" beam and I had to put it into a slip that was 12' wide.

When the winds were blowing hard out of the north I didn't worry too much about how the docking looked, I was more interested in getting the boat in the slip without any major hiccups.

 

[JV II]

With a ton of iron bolted to my transom, the wind and current swing the bow and can be difficult to control. If those 496s were in the center, like an IB boat, that would not happen. I dare say that the thruster in my boat is necessary, and not for weenies. Its kind of like telling someone your rear wheel drive car is for real men in the snow and AWD is for weenies.

 

[Alex F]

Roll up the sides before docking when it's real windy....worth the trouble!

It sure might help, but I prefer to have a good handle and control not to care if the sides are down (they're most of the time). The case I described before was in the middle of the big storm and the rain was pouring. I didn't feel that getting everything wet with the side up was going to help so much. Instead, I tried one approach it didn't work, I backed out of it and changed my tactic. When I was done I felt much better that I was able to handle it. I'm just the kind of guy who will go for extra hassle to get things work the way I like it. If it comes down to learning more I will do just that.

 

[Alex F]

...The technique described earlier of cranking the rudder away from the dock, shifting the far engine to forward and the close to reverse works like a charm -- been using it for years. The engine in forward pushes water against the rudder making your aft want to move towards the dock and the boat want to rotate. The other engine (in reverse) has no effect on the rudder and counteracts the tendency to rotate -- net result if you fiddle the RPMs right: your boat goes sideways. Fiddling the RPMs right takes a bit of practice and of course varies from boat to boat, but its very worthwhile to learn. Once you get it, you'll be able to "walk" your twin inboard sideways like a pro.....

This is very good advice. I'll have to try this trick as it sounds like it could make some docking situations very easy controlled.
Thank you.

 

[Two Peas]

thank you very little...:smt001 As in I told you so.

I really dig the updated signature!