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Rich
12-11-2005, 06:02 AM
I've been searching the net for info on outdrive alignment for twin engine boats but can't find anything. I set up my drives to be straight or parallel. I have counter rotating Alpha 1's. I've heard that for steering, handling, performance, etc. the drives should be toed in about 3/4" meaning the drives should be angled in toward each other. I would appreciate any comments, experience, or literature anyone has on this.

Mr X
12-11-2005, 07:32 AM
IMO, it also depends if you have inboard or outboard rotation.

Rich
12-11-2005, 07:36 AM
Scot
The 3/4" I assumed is the total amount of toe-in meaning 3/8" per drive. That would make the 1/4" your talking about to be 1/2" total. Or did I assume wrong?

Rich
12-11-2005, 07:42 AM
I've got outboard rotation. When facing the props, the starboard side spins clockwise and the port side spins counterclockwise.
Then, is the setup toe-in or toe-out?

Mr X
12-11-2005, 08:07 AM
Agreed. However, doesnt the measurement remain the same, just toe out vs toe in?
Yes.......:)

Rich
12-11-2005, 08:07 AM
OK.........................

For arguement sake, let's make the prop shafts the TOE.
So, on toe-in, the centerline distance from ends of the prop shafts is (+-)1/2" less than the centerline distance of the input or crankshaft?

BTW, my engines/outdrives are 28" on center distance.

Trueser
12-11-2005, 08:16 AM
Another thing you want to check is for play in the linkage. We had to replace all the pins and snug everything down in the drive.

Both our drives our STD rotation and it works fine. Would there be any gains if we had a counter rotation drive?

Mr X
12-11-2005, 08:16 AM
OK.........................
For arguement sake, let's make the prop shafts the TOE.
So, on toe-in, the centerline distance from ends of the prop shafts is (+-)1/2" less than the centerline distance of the input or crankshaft?
BTW, my engines/outdrives are 28" on center distance.
Sorry, I cant decipher that one........???

BUIZILLA
12-11-2005, 08:24 AM
If this was MY boat...

measure the center of the forward edge of the lower gearcase... should be 28"...

subtract 1/4", and that is your measurement to the center of the END of the propshaft. If your sure about the 28" centers at the crank, then the shafts would be at 27 3/4" at the farthest aft point, and the front edge will now be 28 1/4".

Other opinions may vary, read line 1 again. :lookaroun

JH

Mr X
12-11-2005, 08:29 AM
If this was MY boat...
measure the center of the forward edge of the lower gearcase... should be 28"...
subtract 1/4", and that is your measurement to the center of the END of the propshaft. If your sure about the 28" centers at the crank, then the shafts would be at 27 3/4" at the farthest aft point, and the front edge will now be 28 1/4".
Other opinions may vary, read line 1 again. :lookaroun
JH
Jim, that would be TOE OUT.....right:confused: ?

MOP
12-11-2005, 08:50 AM
Another way to skin the cat, not saying it is perfect but it works! I take a front and rear center line measurement on the gear case's not the prop shafts, 1/8 to 3/16" seems to work fine the tips of the prop shafts will show about 3/4" of an inch difference. I get it close then with the help of a co worker load the linkage either in or out depending on rotation to make sure there is good tension on the linkage to somewhat simulate the drives under load, by doing so it helps to eliminate any play even new linkage will have a tiny bit of play.

Phil

BUIZILLA
12-11-2005, 09:08 AM
Another way to skin the cat, not saying it is perfect but it works! I take a front and rear center line measurement on the gear case's not the prop shafts, 1/8 to 3/16" seems to work fine the tips of the prop shafts will show about 3/4" of an inch difference. don't you mean 3/8", instead of 3/4", doing it your way... :stan:

MOP
12-11-2005, 09:26 AM
Jim due to the angle it ends up roughly 3/4" at the prop shaft tips, though only 1/8 to 3/16 at the front & rear case center lines. I have done "ALL" stock setups it has always worked well. On a high performance setup the measurements may be a bit different that I am not sure of.

Phil

Rich
12-11-2005, 09:36 AM
Phil,

The difference in the dimension between the front of the gearcase and the tip of the prop shafts is because of their distance from the pivot point of the drive. The front of the gearcase is very close to the pivot point whereas the tip of the prop shaft is (+-) 23" away.
Make sense?

MOP
12-11-2005, 09:51 AM
Phil,
The difference in the dimension between the front of the gearcase and the tip of the prop shafts is because of their distance from the pivot point of the drive. The front of the gearcase is very close to the pivot point whereas the tip of the prop shaft is (+-) 23" away.
Make sense?

YUP!
Years ago I had tried 1/4" difference from the front of case to tip of prop shaft, on outboards during sea trials they were wiggling and working the tie bar real hard. I sure I/O's act the same way. Maybe I have been doing it wrong, but from that point on I used the gear case not the tips. The force water exerts is super strong, I do not feel 3/16 to 1/4 at the shaft tips is enough.

Phil

Rich
12-11-2005, 10:26 AM
So, here's my plan.
I'm going to adjust the angle of the drives so the centerline to centerline dimension of the prop shaft end is 27-1/4". This will make the toe-in or toe-out(depending on the way you look at it) dimension 3/4" less than the engine/input shafts 28" centerline dimension.
Unfortunately, my boat is sleeping in my neighbor's garage so it will be 4-5 months before the sea trial.

Yeah Yeah I know, all you southern guys could do this today...........

Thank You all for your input.

MOP
12-11-2005, 02:55 PM
On an OB the tie bar is at the front of the engine, unless youre using a rear mount system and external steering rames...

True but any type setup must hold tension on the system underway.

BUIZILLA
12-11-2005, 04:18 PM
So, here's my plan.
I'm going to adjust the angle of the drives so the centerline to centerline dimension of the prop shaft end is 27-1/4". On yours, I would probably go 27 1/2" at the prop shaft, which is 1/4" in, each, at the prop shaft, on each engine. Make sure the gearcase leading edge and trailing edge centers are at 28" before you start though. The center to center on your tie bar should also be at 28" before you start. Measure twice, move once..

JH

Mr X
12-11-2005, 08:15 PM
Why??
Thats kinda what I was wondering this morning on the
last page??
That would be TOE OUT......:confused:

BUIZILLA
12-11-2005, 08:37 PM
Ted, the propulsion (shaft) end is *toe'd in* terminology, the leading edge is toe'd out. This is for props turning outboard config. I would think your ZX is zero to 1/8" toe'd in at the shaft ends, since you have external rams and a tie bar... My Scarab is about 1/8" in at the shaft ends, and I have a tie bar, and i'm purty positive it's been that way for the last 9 years, judging from the hardware.. Rich has Alpha's and NO tie bar.

JH

Rich
12-11-2005, 08:43 PM
Mr. X.....

OK, let's call it toe-out when the prop shaft end is closer together than the normal centerline distance. Is that the way you think the set-up should be?
And what about the distance? 1/2"? 3/4"?

The reason I was picking the end of the prop shaft is because it's an easy object to take centerline measurements from.

Mr X
12-11-2005, 08:46 PM
Jim.....Got ya, I do know that my ZX props turn INBOARD..... and that my propshaft centers are 1/4 inch farther apart than the front tip of my gear cases.
I was taught by Donzi (when I worked at the factory)
they call it TOE IN.
Now I am confusing myself......where did I leave that bottle of Bacardi?

Rich
12-11-2005, 08:49 PM
Pour one for me please

Mr X
12-11-2005, 09:01 PM
OK, just so I know that I am not totally crazy......

Click on this.

http://jimrohr.com/Web%20Pages/Boats-Boats.htm

"Then we measured the toe and heel distance on the Cavitation plate for a comparison of the engines alignment. Something was wrong...it measured a 3/4" difference, hardly noticeable by eye across the length of the long lower unit length on a 150 size engine, but it was there just the same. Now if the engines were "toed in" (front of engines closer than rear of engines) it would be normal for a deep-V hull, but these engines were "toed out" meaning the engines were both driving away from center line if looking forward from transom to bow"

Mr X
12-11-2005, 09:20 PM
Rich, you have to have a tie bar somewhere.....its either inside the transom connecting the tiller arms together, or on the outside connecting the drives together......

MOP
12-11-2005, 09:36 PM
To that end the prop shaft ends should be inboard of center line(closer together). Call it what you want!

MOP

Rich
12-11-2005, 10:11 PM
I haven't noticed anything wierd with the steering while underway,
I just want to dial it in the best I can. When I set up my steering I just made both drives straight ahead.
Attached is a photo of the setup. No external tie-bar

BUIZILLA
12-11-2005, 10:14 PM
Interesting article Ted... if those outboard engines are on the transom, I could agree, on a bracket or extended transom or I'O's, I strongly disagree.

The 3/4" in the article is an extreme offset though... and Aquasport NEVER made a deep V boat as the article stated, modified soft V maybe, minimal strakes with a slightly flat or round, or 11* transom max, but NOT a *deep V* as we know it... way different animal for comparison, I can see that happeneing on *that* hull.

However, the factory installation drawings for the last 5 twin outboard (2 pairs of Yammie's, two pair's of Johnrude's, and one Mercury pair) installs I have read/done/owned, say to do it like I stated. The prop *thrust* should go slightly towards the middle of the hulls immediate wake. The Merc install manual for my 3.0's (manual furnished by TNT) on my last Contender specifically had a drawing showing this, and the suggested preliminary adjustment. A Merc engineer from FonDuLac and Lake X worked on my 3.0's for quite awhile at one point, at the insistence of Custom Engine Service (warranty service center) and Champion Marine (where I bought them), and he told me *don't let ANYONE* tell you differently with *outboard turning props*... That boat went 67 mph rocket straight, once we toe'd out the leading edge by only 1/4" total... Both of my Yammy twins on 2 other Contender's had the factory Yammy drawings showing this. My 321 Intrepid with Johnson's was factory done the same way. And, my current 302 Scarab is basically done this way. That's 5 boats with POSITIVE results that I personally owned. My Service Manager has had 4 Scarab's, 1 Action and 3 or 4 other 25-34 twin outboard boats, and they were ALL factory rigged with the shafts closer than the leading edge, except one. In fact, that one boat he had was so uncontrollable/spooky with the leading edge toe'd in, that he was almost thrown out of it twice, and on one occasion he was actually thrown to the floor, and was bruised terribly, (we surmised that toe'd in at the front was making the TWO engines *think* they were ONE rudder) so all we did was set them to 1/4" in at the shaft ends, steering then went neutral, rocket straight at 78 mph, and it was perfect manners after that. And, *I* will continue to do it that way...

A stepped bottom, with inboard turning wheels, like yours, may be different though, I've never owned one to experiment otherwise. I meakly plead the 5th on that one.

I know what worked for me, so i'll just shut up now, and mind my own business in the future. :biggrin.:

JH

Mr X
12-11-2005, 10:48 PM
Jim, I know each hull and set up are different.....
I agree with what ever works best on any given set up.

I am not disagreeing with you.......

I know NOTHING takes the place of experimenting and trial and error.

Your data proves that it works best for boats of that type.

Now I am wanting to try a few different settings on mine.......:biggrin:

I have seen so many boats that came out of the same mold.... require different settings and props!

I dont think anyone can easily explain that one:confused:

BUIZILLA
12-12-2005, 08:03 AM
Ted, i'm anxious to know your tests, and results, with your ZX. I *know* you know what your doing, so please share.

JH

Greg K
12-12-2005, 09:00 AM
From what I've read is that most 'conventional' V-bottoms work best with a small amount of toe-in (front of drive vs. end of prop shafts). This is because the flow of the water is being parted by the V slightly outwards as the boat moves forward.

When props turn outward, the load tends to cause the drives to tow in a small amount. The condition and slop in your transom assemblies and gimble ring will determine how much it'll move.

Turning props in, will have the opposite effect.

So, for a small amount of toe in while running turning props outwards, start with them parallel.

For step and ventilated V's, running the drives parallel are a general rule underway.

Prop rotation and type of hull will determine how your static setting will initially be set.

turbo2256
12-12-2005, 11:42 AM
I like this

Greg K
12-12-2005, 12:02 PM
On the alpha's, there is also a certain amount of flex built in, hence my reccomendation to try toe in. The boat will track better, but might lose a MPH on the top. It's a 7 meter, a quite heavy and deep V, not a light, moderate V.....

If that's the case, parallel to 1/8" toe in (static) would work well with props turning outward.

turbo2256
12-12-2005, 12:34 PM
On my Apache the props turned out board the drives were heeled in approx 1/8 per my illistration. The boat handled a bit strange. Kind of got caught surfing a wave and seemed a bit touchy at times.

Contacted the Chief. Was told outward rotation is the way to go but heel out as shown on my illistration about 1/8 " set it to 3/16 heel out handling issues corrected felt much more relaxed at the helm. Will be dialing it in a bit more this season will try 1/8 next since the linkage is very tight the looser it is the more needed just like a car.

MOP
12-12-2005, 03:29 PM
Sure looks like I have may been doing it wrong for many years, it was our OMC Tech Rep that had instructed us to do it that way. His said we needed to understand that the wash off any transom comes upward, on a deep V hull it comes upwards and inward toward the center of the transom. He said just look at how single deep V's wag at low speed the wag was due to the wash coming inward and upward kicking the drive side to side. It sure made sense, I knew by dropping the tabs or raising the drive the wag stops. Will be watching for Teds input on his.

Phil

Mr X
12-12-2005, 05:43 PM
I hope to try it in a couple weeks.......I will keep you all posted.

joseph m. hahnl
12-15-2005, 05:13 PM
WOW: twin inboards run straight on center> HMMMMM? could it be the only reason you tow an out drive or out board is due to slop in the tie bar. it seams that nuetral is the way to go. that you would want the props perfectly straight under power and the tow is to compensate. So if this is true
than you want to adjust the tow opposite of the prop torque. meaning if the if the props are trying to pull out ward you tow in. if the props are are tring to pull inward you tow out. but in any case you need to stick to one side of the drive and i agree with MP measuered from prop side.
It is easiest to measure frome the prop hub > centerline would be from the outer side of the right prop hub to the innerside of the left prop hub.

as I don't have twins I don't need to worry about it.I think to fully understand how to do it. Is to Know why you are doing it. if you understand the physics then you understand the principle. Then all you need to do is apply logic.


joe