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Author Topic:   Toe-in Adjustment on Twin Outboards
Rick U posted 03-12-2003 05:40 PM ET (US)   Profile for Rick U   Send Email to Rick U  
What is the proper toe in adjustment for counter rotating outboards? My new 250HPDI's are installed and they look pretty pigeon toed. Hope to start the break in process tomorrow.

[UPDATE: for more on this topic of toe-in adjustment for twin engine outboard boats, see a more recent article in the REFERENCE section--jimh]

lhg posted 03-13-2003 02:41 PM ET (US)     Profile for lhg    
The tie bar should be adjusted to be about 1/4" longer, maximun, than the engine centerline dimension.
Rick U posted 03-13-2003 08:52 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Thanks, is that measurement the same whether using the inside or outside holes on the steering tongues? I am using a new single ram hydraulic and its tuck in tight.
Tom W Clark posted 03-13-2003 11:09 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
If the tie bar is 1/4" greater than the engine o.c. dimension, wouldn't that result in toe-out instead of toe-in?

For a give length of tie bar the amount of toe (in or out) will vary depending on what hole position in the tiller arms you use. I would think the point of reference would be the difference between the leading edge of the gearcases versus the distance between the trailing edges.

Is the amount of " toe" an outboard manufacturer's recommendation or is it Whaler's recommendation? If the latter I would think a quick call to Chuck Bennett would answer the question.

Exactly what is the purpose of not having the motors parallel?

Rick U posted 03-14-2003 12:09 AM ET (US)     Profile for Rick U  Send Email to Rick U     
“Exactly what is the purpose of not having the motors parallel?”
I have tow guesses.
1. The boat will have better handling when the “outside” motor is turning harder.
2. directing the power into a “V” behind the boat has some benefit while going straight.
I assume (if these guess have any merit at all), they come at the expense of efficiency. If I better understood the principle, I could dial the adjustment into my needs.
Rick U posted 03-15-2003 11:44 AM ET (US)     Profile for Rick U  Send Email to Rick U     
While launching the boat yesterday, a Yamaha mechanic came over and said, “You have too much toe-in”. I asked how much is recommended and his formula was 1-inch for motors mounted 26” apart. My motors are mounted 29 apart. He said the prop wash should “V” 20 meters behind the boat. Anyway, the motors ran well but I had the keep the RPM’s low for the ride home because they are breaking in. I did notice the “V” about 1 foot behind the boat and keeping the boat heading straight required constant turning.
jimh posted 03-15-2003 12:30 PM ET (US)     Profile for jimh  Send Email to jimh     
Why have toe-in? My guess is that by having the thrust directed slightly off perfect center line, the two motors exert a slight tension on the steering tie rod. The tension keeps the motors from rocking back and forth because of slop in the steering mechanism, as might happen if they were aligned.

If the wakes converge at 20-feet behind the boat, and the engines are separate by roughly 2 feet, this implies a toe-in of

toe-in = ArcSin(2/20)

toe-in = 5-6 degrees

jimh posted 03-15-2003 12:35 PM ET (US)     Profile for jimh  Send Email to jimh     
Opps. The wakes converge 20-meters behind the boat says our metric system mechanic. That is about 60 feet. The toe-in should be:

toe-in = ArcSin(2/60)
toe-in = 2-degrees

(Ask those scientists at the Jet Propulsion Labs about mixing measurement systems in a project. Cf.: )

jimh posted 03-15-2003 12:40 PM ET (US)     Profile for jimh  Send Email to jimh     
Re Efficiency:

Misdirecting the thrust by 2-degrees would otherwise tend to waste about 3-percent of the force, but since both motors are directed inward, you could assume they cancel each other. Their composite thrust comes out on centerline.

Another point to consider: are the engines counter rotating or not? How does that affect the decision to toe-in?

jimh posted 03-15-2003 01:57 PM ET (US)     Profile for jimh  Send Email to jimh     
Another concern with specifying the toe-in dimension as a particular amount of offset in inches: it depends on how far your tie bar is located forward of the engine pivot point.

Some engines have a tiller arm extension tang that is used with the tie bar, moving the tie bar farther away from the pivot point of the engines.

If my tie bar is only a few inches forward of the pivot point and your tie bar is twice as many inches forward of the pivot point, we will get different amounts of toe-in when we adjust the tie bar for a particular number of inches.

I think the engine makers specify this amount, at least Mercury does I believe, in their instructions for using the tie bar.

Also, I have to correct myself in an above post. If the engines are toed-in then the tie bar mechanism is put into compression not tension by the offset engine thrust.

Rick U posted 03-15-2003 03:22 PM ET (US)     Profile for Rick U  Send Email to Rick U     
The motors are counter rotating. If the 2-degree offset were the number then I would measure that at the leading and trailing edges of the lower units and not have to worry about tiller bar holes. One more thing to consider. Is the 20 meter rule the same regardless of speed?
Sal DiMercurio posted 03-15-2003 05:57 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
What [I have] always done is [to] connect one engine to the steering bar and leave the other loose.
Give the connected engine full throttle & the dead engine will find the correct track! Then connect the dead engine to the steering rod.
jimh posted 03-16-2003 11:18 AM ET (US)     Profile for jimh  Send Email to jimh     
That is a good observation from Rick regarding the affect of boat speed on the distance the wakes should converge.

Sal's in situ adjustment procedure sounds interesting. This approach forces me to make the assumption that the position of the dead engine would not change at all if it were being operated at full power, too.

This also ignores the effect to propeller torque and the effect of the convergent thrust.


captbone posted 03-16-2003 12:44 PM ET (US)     Profile for captbone  Send Email to captbone     
I would NOT run the dead engine at any power, I had a tie bar come apart while running and the engine with no coneection went searching from side to side banging hard against the stops as it did. To the let the dead engine drag will be fine because the water pressure will keep into place but any power will be dangerous. Also to everyone running with twins, make sure the props spin outward on counterrotating motors and not in. You will have a much better running rig with the engine turning out. Turning in, you will get a higher top end but a more squirrelly rig. Just my 2 cents.
jimh posted 03-17-2003 09:12 AM ET (US)     Profile for jimh  Send Email to jimh     
Chris Caswell, a well-known writer on boating topics, recommends having no toe in or toe out, citing a waste of power and inefficiency.


jimh posted 03-17-2003 09:32 AM ET (US)     Profile for jimh  Send Email to jimh     
More searching turned up this article, attributed to Mercury Marine, which recommends that twin engines on vee-hull boats be set parallel, no toe-in or toe-out.


jimh posted 03-17-2003 09:39 AM ET (US)     Profile for jimh  Send Email to jimh     
Here is a very interesting narrative of a professional marine consultant adjusting tow-in /toe-out on a twin engine outboard boat:

jimh posted 03-17-2003 01:20 PM ET (US)     Profile for jimh  Send Email to jimh     
After reading the several off-site articles I mentioned above, it seems to me that toe-in is a case where the front of the engines are closer together than the back, and toe-out is the opposite, where the front of the engines are farther apart than the back.

This seems to be in conflict with the way it has been used by several of the authors in this thread. I am going to review this again and then perhaps edit the articles above to conform them to this usage of toe in/toe out.

Rick U posted 03-17-2003 04:12 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Now I'm confused
jimh posted 03-17-2003 10:42 PM ET (US)     Profile for jimh  Send Email to jimh     
If you follow the "toe" metaphor, then it seems to me that a condition of toe-in implies that the front of the engines are closer together than the rear. This makes the thrust of the engines non-convergent, that is, the propeller thrust should spread apart slightly behind the boat.

Jim Rohr uses the expression in that sense in his article.

Continuing the metaphor, toe-out implies the engines are closer together at the rear than at the front, causing the thrust to converge at some point.

Anyone agree with that use?

Also the use of the term "Vee" or "V" to describe the wakes that result is confusing because no one specified if the wakes were converging or diverging in a vee.

One thing is for sure; when you have twin engines there is always something to tweak and adjust!

lhg posted 03-18-2003 05:31 PM ET (US)     Profile for lhg    
JimH I think the article writer is wrong.

The use of the "toe" wording comes from a person standing up. Assume the person is the outboard, facing backward, looking down at the anticavitation plate, which would be your feet. Toe-in would mean pointing your feet (toes) in.

All of the Mercury racing guys that I have spoken to indicated that a SLIGHT toe-in increases speed. That's where my 1/4" tie bar recommendation came from. It is an EXTREMELY slight toe-in at the props, which can't even be seen visually. Evidently converging thrust is faster than diverging thrust.

Barry posted 03-18-2003 10:07 PM ET (US)     Profile for Barry  Send Email to Barry     
I also assumed that the person was the outboards. However I assumed that the person (outboards) faced forward toward the bow of the boat.

Here is what the OMC Installation Instructions for the Adjustable Steering Tie Bar Kit says.

"The adjustment feature also allows you to create a toe-in condition between dual engines (bring the forward portions of the engines together slightly). This is very important if your boat has a deep V shaped hull. Because water does not pass straight to the rear off the bottom of a V shaped hull, but slightly towards each side of the center of the hull, a slight toe-in of the engines will align the engines' lower unit (gearcase) with the true direction of the water flow. This alignment with water flow allows the propeller to grip the water cleanly, more efficiently, resulting in improved boat performance."

Currently my 150's toe-out, so I will be adjusting them before I put it in the water.

Barry posted 03-18-2003 10:16 PM ET (US)     Profile for Barry  Send Email to Barry     
The instructions also say:

"The precise amount of toe-in required depends oupon the degree of V-shape of the boat's bottom. As the V-shape gets deeper or steeper, the amount of toe-in must increase. Proper toe-in adjustment can result in better boat performance and lower steering effort. The correct amount of toe-in for your boat and engine combination can only be achieved by making successive runs with varying degrees of toe-in."

It states the 1/2 inch of toe-in is appropriate for many V hulls and suggests starting from that point.

lhg posted 03-18-2003 10:35 PM ET (US)     Profile for lhg    
Well, I am completely confused, but tend to think the OMC people should know what they are talking about. So maybe my advice should be ignored. I think I will try this OMC adjustment and see what happens.
Rick U posted 03-18-2003 10:40 PM ET (US)     Profile for Rick U  Send Email to Rick U     
As it turns out, I’ll have to cut my tie bar to achieve the proper setting. I thought my motors were originally set at 39.5’ on center but I can’t find anything to back that. I’m thinking I want to cut the bar to allow equal adjustment either side of parallel. I’ll disconnect the tie bar but how will I get the motors square so I can determine how much to cut? (the boat is in the water and I don’t have a trailer) I assume the starboard motor will have to be steering dead center or the measurements will be off. Any thoughts?
jimh posted 03-18-2003 10:50 PM ET (US)     Profile for jimh  Send Email to jimh     
Many thanks to Barry for including the quoted material from OMC. The comments about the vee-hull bottom and the direction of the water flow provide some jutification for mounting the engines slightly off from dead-center.

By the way, there is much discussion in that Mercury hi-performance article about giving consideration to the cooling water pick ups and how they are affected by the flow of water off the vee-hull bottom at high speeds.

In all, an interesting discussion!

Barry posted 03-18-2003 10:50 PM ET (US)     Profile for Barry  Send Email to Barry     
The Instructions suggest taking the front measurement between the steering arms and taking the back measurement between the center point on the rear edge of the anti-ventilation plate.

I don't know if you could tilt the engines up and get to the rear of the anti-vent plate to measure. If not then I would leave them down and use a point on the rear of each cowling.

lhg posted 03-18-2003 10:56 PM ET (US)     Profile for lhg    
To find the engine centerline dimension, you will have to measure from some place on one engine, to the identical place on the other.

The engine bolts could work for you on this, if they are exposed. So could a place on the engine bracket. It has to be some place on the engines that don't swivel (turn), and are permanently fixed. You could trim the engines all the way up, and run a tape from one bracket edge to the same place on the other one.

On Classic Whalers, the most common engine centerline was 29 3/4" (18, 20, 22 & 25) Most have a decal indicating this. On the 27's, I think it was 28", as it also was on all WD's. Aftermarket brackets like Armstrong often use 27" or 26", usually the minimum that can be used with conventional hydraulic steering. On my 25, 27" was used.

Sal DiMercurio posted 03-18-2003 11:52 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
IHG, good post, very informative.
Rick U posted 03-19-2003 12:57 AM ET (US)     Profile for Rick U  Send Email to Rick U     
"I thought my motors were originally set at 39.5’ on center but"

Woops, I meant 29.5. typo

Rick U posted 03-29-2003 09:40 PM ET (US)     Profile for Rick U  Send Email to Rick U     
After reading lhg’s post, I felt confident enough to take a hacksaw to my tie bar. The motors measured 29 ¾ so we disconnected the tie bar and moved the port motor till the tiller bar was 29 ¾ “ from the center of the other tiller bar. We marked the tie bar and cut off about 1 ½”. The motors are now parallel and have plenty of room to adjust “toe-out”. In order to achive “toe-in” (propellers veeing away from each other) we’ll have to cut more off the bar. I’ll try it like this first as I can always cut more later. We really wanted to take her out today and get into the throttles for the first time but the wind and waves were up so that’ll have to wait till next weakened. Thanks again to everyone who scratched their head, looked at their set up, searched the Internet, looked through old manuals, and helped me think this through.

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