Before Posting, Please Read Our Posting Guidelines Below.
1. Use the full 4 digit year for everything you are asking your question about. Example: 1962, 1988, 2000, 2011 2. Include the correct name of your Whaler model. Example: Montauk 17, Montauk 170, Outrage 26, Outrage 260 3. Include the length when necessary. Example: 16, 17, 18, 20, 22 4. Do not post your email address anywhere on this site as it is already in your user profile.
So, using the images Tom what you are describing is:
Example A is "Toe In"
Example B is "Toe out"
(SEE PREVIOUS PAGE FOR EXAMPLE A and B IMAGES)
I have read all kinds of posts from a bunch of sites this evening (scream and fly, offshore only, the hull truth, a couple Australian fishing sites and a couple others.) and found all kinds of differing opinions. Also, it seems that every manufacture regards the definition of toe in / toe out differently as well as what they recommend to be correct. Some guys cite Yamaha and Mercury manuals that say the thrust as it leaves the props should met together behind the boat some 75 feet behind the boat. Well I guess that tells me they should be set up per the Example of B above however, as speed changed wouldn't the meeting point change?
Some guys who are running large horsepower offshore center consoles claim the setting should depend on which way your props counter rotate together. If tops of the spin toward the centerline of the boat then you should be toe out and just the opposite if they turn the other way though nothing clear was given as fact on that nor cited any manual. However, if that is true what happens when you have a boat like ours where both motors turn clockwise in the same direction?
Now with the Ackermann steering principles each situation can institute different turning dynamics. This was talked about in a discussion I found on the Australian fishing site and this was my take away from it. In Example A the inside motor because of it's increased turn in will drive the inside stern down as it fights the outside motor and causes the boat to roll into the turn. If you have a boat that feels like it wants to dart and heavily roll into a severe pitched turn you can counter act those forces by setting up the motors as shown in Example B where the outside motor is providing the greatest force to turn the boat and flatting out the roll of the boat.
I guess after reading everything I have this evening and thinking about it really, the best and most often cited way to determine how you should set up the motors is to just disconnect the tie bar and let the motors find their own true course. I can see in my mind reasons why one would want to set a boat in both situations however, why think for your boat...just let it decide for itself.
Tom, hope I have not driven (nor are still driving) you crazy....
It is my understanding from my reading that a true parallel setting could create a flutter in the steering thus creating a sloppy steering feel as well as possible vibration feedback.
Also these settings are accomplished through the adjustment of the tie bar length. In essence the tie bar can be adjusted making it either shorter (Example A) or longer (Example B) through an adjustment fitting usually at one end of the bar.
... a true parallel setting could create a flutter in the steering thus creating a sloppy steering feel as well as possible vibration feedback.
No, that is not true.
If the water flow past the motors is perfectly parallel, then the motors should be set parallel.
The amount of toe is very small. Strictly speaking, we should be talking in angular units, degrees of alignment, but because that is hard to measure we use distance between fixed points on the motors.
The points of reference we use is the leading edge of the gearcase and the rear of the propeller shaft or hub of the propeller. Because most large outboards have very similar physical sizes, this system works.
Typical toe dimensions are less than one inch, so the angular variation is very small.
The answer the question of how alignment or misalignment manifest it self, the answer is: Very subtly. It is not a profound difference unless the motors are grossly out of alignment.
The typical effect of excessive toe-out is a tendency for the boat to list to one side or the other and stay there, flopping over the other way after a course correction.
My own 25 foot Whaler had the motors set parallel when I bough it for its original owner. I had noticed a very slight tendency for the boat to sort of roll due to a wave and stay there a wee bit longer than I though it should. After discussing the motor's alignment with Whaler Customer Service (Chuck Bennett) I was told the motors should have their leading edges of the gearcases about 1/2" to 3/4" closer together than the rear of the propellers.
I now have set my toe-in set to 5/8" and have noticed a slight improvement to the laterally stability of the boat in sloppy conditions as a result.
OK, the Ackermann steering principle. I am not buying it Jeff for a lot of reasons, not the least of which is that boats move through water, a fluid, not over a road, a solid flat surface.
For starters, cars deal with the Ackermann steering principle by having steering geometry that varies as the steering input varies. Boats do not. The steering in (most) boats is designed to accommodate travel on a straight course. It is not set up to accommodate sharp turns at the expense of straight line handling.
Your drawings do not show the flow of water under the boat and by omitting this suggests it is parallel to the keel. IT most certainly is not parallel to the keel during a turn. As we all know the stern will be sliding (sometimes quite a bit) after entering a turn.
In Example A the inside motor because of it's increased turn in will drive the inside stern down as it fights the outside motor and causes the boat to roll into the turn.
The inside motor will have a GREATER angle vertical thrust component because it is partially laying on its side with its gearcase acting like a trim tab to LIFT that corner of the boat, not drive it deeper. Again, remember we are talking about VERY SMALL variations in the angles of the motors. In the context of this phenomena on these boats, it is going to be irrelevant to the lateral attitude of the boat in a sharp turn.
Hey, everybody likes to research things with Google, few more than I do. However, there are guys down in Australia right now Googling and arguing about motor alignment and citing an expert named Jeff who produces fabulous drawings and diagrams!
The take away: Be careful what believe on the internet.
If you want to see how your own particular boat performs with different toe settings, go ahead and experiment as I have.
I never claimed anything I read was gospel only that there are all kinds of varying opinions and a lot of theories. That is why I stated in the end I thought disconnecting the tie bar would most likely be the best way to correctly set up a boat. Period. I never stated I thought I was smarter than you or anything like that. Certainly never claimed to be an expert and stated lot of my ideas come from the days of setting up cars. I know they live in different worlds and I agree with that. However, it is tough to overcome those ingrained ideas. One thing I will say even though a car is always moving on a solid surface there will always be tires that slipping a bit over that solid surface. Nothing like a liquid environment though.
None the less, this spring I hope to mess around with these toe in toe out settings on the guardian and just see what it does for S&G's. Like you stated experiment with it to find out what works best. The boat is getting derigged so it can get soda blasted, painted, as well as to having all new control cables installed so why not. I will try setting first by disconnecting the tie bar while running on plan to fit it's natural flow and go +/- from there. I would assume the boat will end up being set much like yours, who knows.
The Ackermann steering relies on the tie bar being shorter than the distance between the two pivot points. Now I don't have twins but I believe most tie bars on outboards are mounted centerline to the pivot points of the engines. This will cause the engines to remain parallel or at the same angle to each other (toe will not change) at all steering angles.
Tom Clark has identified the correct nomenclature for toe-in and toe-out. Picture yourself standing on top of your motors, facing forward, with your left foot on the port motor and right foot on the starboard motor. If you move your toes "in" and the motors were to follow, the propellers move further apart and the respective wakes would never converge. And conversely, if you move your toes "out" (and the motors follow) the propellers move closer together and the wakes would converge at some point behind the boat.
You may want to check and see what Mercury recommends. Yamaha recommends a "toe-out" position of less than 1 inch such that the wakes converge approximately 75' behind the boat.
Yes, I have seen that advice in an old Yamaha rigging manual myself. That advice is very odd because toe depends on the boat, not just the motors. Yamaha can't just offer generic advice like that without knowing the particular situation.
I have also seen Yamaha literature recommending the motor mounting height be such that the AV plate of the motor be one inch below the keel to keep it completely submerged.
Yes, I would agree that the boat manufacturer would be a better source for toe-in, toe-out recommendation taking into consideration the specific design characteristics of a given hull.
