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Rich
06-05-2006, 08:15 PM
My buddies boat with twin alpha 1's and cable steering pulls to port. The faster you go, the stronger the pull. You actually have to turn the wheel about 1/2 a turn to starboard to keep the boat straight. If you let the wheel go, it turns to port really fast. There is no tie bar or zinc skegs on the drives. There is adjustable connecting link from steering arm to steering arm but that is to adjust the drives for toe in or out. We checked the drive alignment with the steering wheel centered and they appear to be pretty straight. We were going to keep adjusting the steering cable at the inner transom plate until it straightened the pulling out, but I thought I'd ask here first. Any suggestions?

MOP
06-05-2006, 09:33 PM
by your description feel the boat has both drives turning the same direction IE: both right hand rotation. You need to have the fin type zinc tabs the flat plates with twins is a night mare, with the fin can be adjusted to cancel out the torque. It will not cancel it out at all speeds, normally I adjust them for a speed just a little above normal cruise, set the trailing edge of the tab offset to the right. The tabs act like a tiny rudder, they do scrub a tiny bit of speed but sure do give your arms a break. Don't get carried away kick them over about 1/2" off center to start, I think about 3/4" with get you where you need to be but all react a little different.

Phil

Rich
06-06-2006, 11:32 AM
Phil
Unfortunately I left off the fact that they are counter-rotating drives. That's why he left the zinc fins off. He thought they would cancel out each others pulling tendency. We're going to give the fins a try anyway.

Barry Eller
06-06-2006, 06:07 PM
The amount of positive or negative trim of the outdrives changes the load on the propellers torque. Try adjusting the trim of the outdrives untill you get neutral steering. With the drive all the way down will cause the pull in one direction and trimmed up will pull in the other direction. Find some where in the middle and the prop torque steering should diminish.

MOP
06-06-2006, 10:01 PM
Phil
Unfortunately I left off the fact that they are counter-rotating drives. That's why he left the zinc fins off. He thought they would cancel out each others pulling tendency. We're going to give the fins a try anyway.

It is possible that the actuator/shuttle valve on the power steering ram may need adjusting to balance it, get your hands on a manual Seloc or Merc both have a very good discription. It is a simple job there is a cap with an adjusting nut under the tin cap on the drive end of the steering ram. Follow the instructions to a "T" it is fairly easyu to ruin the locking feature of the nut, if my flat bed scanner was working I would post the instructions. It is good to see the diagrams and do a step by step, takes 15-20 minutes to get it set. Now I am hoping the hull is not the cause, we had a brand new Grady that drove us crazy until we did some straight edging of the bottom which showed a 1-3/4" twist in the last 1/3 of the hull.

Phil

Barry Eller
06-06-2006, 11:19 PM
It is possible that the actuator/shuttle valve on the power steering ram may need adjusting to balance it, get your hands on a manual Seloc or Merc both have a very good discription. It is a simple job there is a cap with an adjusting nut under the tin cap on the drive end of the steering ram. Follow the instructions to a "T" it is fairly easyu to ruin the locking feature of the nut, if my flat bed scanner was working I would post the instructions. It is good to see the diagrams and do a step by step, takes 15-20 minutes to get it set. Now I am hoping the hull is not the cause, we had a brand new Grady that drove us crazy until we did some straight edging of the bottom which showed a 1-3/4" twist in the last 1/3 of the hull.
Phil


I understood that the boat had cable steering. Power steering does not give as much feedback from prop torque that drive trim angles change. I'm not saying that your suggestion is wrong, you are right about power steering doing that. Cable steering gives all prop torque back. Something about changing the load from the top blades to the bottom blades depending on trim angle causes the torque to pull the boat port and starboard.

MOP
06-06-2006, 11:29 PM
Barry with counter rotaters they cancel each other out, what you are saying does apply to a single. But DCR has me thinking about the possiblilty of the valve being off or just plain not functioning right. By rights it should be a hands off rig at most any speed.

Phil

BigGrizzly
06-07-2006, 07:21 AM
What is the Toe in or out on the drives also what boat are they on>

Carl C
06-07-2006, 08:31 AM
On outboards we'd use torque tabs that screw to the skeg. The trim tab that Mop mentioned would be out of the water at WOT. Not sure how this relates to an IO. Torque steer is usually caused by the prop being trimmed one way or the other causing uneven loading of the blades. This would also eat up prop shaft bearings and retainers on outboards if they weren't beefed up.:lifeprese

Rich
06-07-2006, 01:27 PM
Thanks for all the input
There is cable steering - no power steering
The props are spinning out - port is CCW, starboard is CW
I'm not sure of the boats maker (Caravelle or Cavalier I think) but it has a pretty deep V hull.
Since he is still working on this boat there are no trim guages yet so the drives have been trimmed in or all the way down at all speeds. Because of the twins and lack of trim guages, we can't tell where the drives are in relation to one another while on a run. During our runs we would lose track of how far up or down each drive was and would go back to trimming all the way in and start over. I think for now, we will trim the drives up a bit and then make a run, trim up some more, make a run, to see how the steering is affected. I still find it hard to believe that twins trimmed all the way in would cause a pull to either direction. I would guess a canceling effect should be taking place.

Formula Jr
06-07-2006, 04:27 PM
They should cancel eachother. Things to check:

That Both props are identical aside from being right hand and left hand.

Use a measuring stick or block to set the two drives to identical trim
before testing. Then don't fool with them. It doesn't appear to be the trim anyway.

Can you balance out the pull by using different settings on the two throttles?
Are the two rpm readings the same when the throttle handles are matched?

Sounds like the Clockwise prop is dominant if its pulling to Port.

Lastly and this may sound weird, but I'd check it anyway, see if the gear ratios of the two drives are the same. I'm assuming your friend just bought this boat.
The difference beween a 1.5 and a 1.65 or a 1.98 and a 1.84 can be subtle.

To really give a good direction we need to know which of these three ways the counter clockwise drive is set up. From the post this is the port drive.

A. Is it one of the very rare Left Hand CCW Alphas. People say they exist, but I've never seen one.
B. Is the Port Engine set up to run backwards with a normal Alpha and a CCW prop.
C. Is the Drive being run in Reverse with a Lefthand prop.

If both engines spin the same way, we can eliminate B.
If they spin different we can eliminate A and C.

Or you could have some really crazy combination going on.

Did the guy that sold the boat have really baggy brown pants and look like he lived through the Depression, wear a funny hat, and constantly mutter something about one drive being just as good as another.......

Let us also know what engines are being used and if they are four barrel carbs
and if the threads for the prop shafts are the same rotation to tighten or different handedness.

Its unlikely that these drives are original to the boat if its cable steering.
Are you sure they are Alpha 1s?


I finally get to say something before Phil answers it! Yeah!!!!

Rich
06-08-2006, 07:27 PM
Owen

Well, we didn't check everything but..........

They are definetely Alpha 1's with the port side being a counter rotating model (yes, they do exist). I've got one also on my 7 Meter

The props are exactly the same but one is LH & the other is RH

The drives were bought new and he ordered the same ratios....we'll check

RH thread on both prop shafts (can't fiqure why this matters but.....)

The engine RPM's mmmmmmmm....pretty old tachs....we'll check

Rich
07-06-2006, 03:13 PM
We checked everything.......twice. All was good. Since his transom assembly was an old style that had holes for a bolt that you can set the minimum trim "in" with, we found the second hole worked best. Then we put the little zinc fins on the drives with the trailing edge turned slightly toward the port side. It worked perfectly. The boat now has neutral steering at all speeds. Since these are counter-rotating drives, we dismissed this as a solution since we thought steering torque would we be cancelled out. Since it worked, we decided to stop thinking about why and just have fun with the boat.

Thanks for everyone's thoughts and ideas.

Trueser
07-06-2006, 03:48 PM
I have a Z29 with Alpha 1 Gen 1 both right handed with NO Problems. My zinc tabs are flat. But I do have a Tie Bar.

Good luck.