Alpha I gen II drive pulls hard left @ WOT

bear_69cuda

bear_69cuda

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Oct 10, 2008
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Morning gang,

So I?ve researched trim anode tab adjustment, and fully understand that if steering pulls to the left, the tab should be adjusted to the left (/) looking down facing prop. Water pressure should push the boat to the right counter acting left pull. But this doesn?t seem to help. My boat does this only at WOT with my stainless 14.25 x 17?P Stiletto advantage II. When I have my stock prop 14.25 x 21?P aluminum it does not pull to the left. When going to stainless prop I needed to change trim anode from stock style to this type.

http://www.iboats.com/Quicksilver_A...6066718--**********.903842687--view_id.166968

Do you think this tab would be less effective than stock type? It seems to have less surface area?

When cruising ~ 20-30 mph there is not much pull, but at WOT if I let go of wheel, the boat would be in a massive port spin?

Also I?m running smart tabs?.

1999 Alpha I gen II.

Any ideas or theories would be great!

Thanks!
 
ken_23434

ken_23434

Petty Officer 1st Class
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Jul 28, 2008
Messages
313
Re: Alpha I gen II drive pulls hard left @ WOT

If I understood your post correct, I think you put the trim tab the wrong way.

Looking down (from above) and standing behind the prop, I think the front of the tab should point TO THE LEFT ( \ ) to correct a problem of the boat pulling to the left.

Now, as far as your problem being related to only the one prop and not the other, I am not sure. I know there is a phenomina (is that spelled right?) where the prop "walks" and causes a sideways thrust as it rotates on single prop boats. Maybe this effect is more pronounced with the one prop over the other due to it's shape? Just a guess.

I would have the correct size wrench for your trim tab on the boat the next time to run it. Shut down the motor, trim it up, loosen and adjust the tab, then give it a test drive. See if it is better or worse and go from there.
 
ken_23434

ken_23434

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Re: Alpha I gen II drive pulls hard left @ WOT

bear_69cuda said:
According to my Service Manual, and this along with other threads, the trailing edge (aft of the tab) should be pointed to port side. And I'm all the way over.

http://forums.iboats.com/showthread.php?t=287736&highlight=adjusting+trim+anode

This dude had the exact same issues.... But never posted resolution... :(
Click to expand...

Well, I see the other posts recommend the opposite of what I did. But, it doesn't make sense to me.

If you want to turn a boat to the port, the trailing edge of the rudder will be positioned to the port side, correct?

I view the trim tab as a "little rudder". Seems like it would cause torque in the same direction as the bigger rudder (the drive).

Experiment with it on the water till it works right. Then post your results.
 
bear_69cuda

bear_69cuda

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Re: Alpha I gen II drive pulls hard left @ WOT

I thought the same thing, but higher water pressure with speed hits the tab set like this (/) and pushes the stern of the boat to the starboard side.. Since this tab is a rudder, this should counter act my pulling left or port... But no dice... a rudder works by altering the flow of water around it so that one side begins to experience greater pressure than the other. If the rudder is swung to starboard (right \ ), for instance, pressure on that side will increase and lessen on the other. As a result the stern, or tail end, of the boat will swing to port (left / ) and the bow, or front, to starboard

Someone please verify my feeble brain... :redface:
 
cr2k

cr2k

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Re: Alpha I gen II drive pulls hard left @ WOT

It works like the trims on an airplane. They DO NOT turn the boat L or R they put pressure on the drive to go in the opposite direction you turn the tabs.

So if your boat wants to turn L move the BACK of the trim tab L which will pressure the drive to turn R.

the one you showed was the HP one? The one that hangs back or the regular one that is a small triangle?

And yes SS props do have a little more torque steer associated with them.
 
havasuboatman

havasuboatman

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Mar 5, 2009
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904
Re: Alpha I gen II drive pulls hard left @ WOT

Go back to where your shift cable attaches to the power steering unit on the transom assembly. The tube that the cable runs thru has two flattened areas that are opposite each other. these are for holding the tube while tightening the steering cable nut. These flat areas must be aligned so that one is facing forward, and the other facing aft, so that a wrench would be slid down from the top.
If yours is 90 degerees off, give or take, the valving in the power steering unit is misaligned and will cause the boat to turn hard to port at WOT.
To remedy this, loosen the steering cable, rotate the tube into the correct position and hold it there while tightening the steering cable nut.
 
bear_69cuda

bear_69cuda

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Re: Alpha I gen II drive pulls hard left @ WOT

Spoke with Mercruiser service dept at local marina, and they say $230 for outdrive alignment? Anyone think this sounds correct?
 
ken_23434

ken_23434

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Re: Alpha I gen II drive pulls hard left @ WOT

Wouldn't a Non Feed Back helm prevent the outdrive torque from turning the steering wheel? I think they run about $100.

I don't have one on my boat, but from my understanding, the NFB helms keep the steering wheel locked in place (ie you put it in a turn and release the wheel, it stays in a turn) unless the steering wheel is used to reposition the steering. The reaction from the outdrive cannot move the steering cable and the steering wheel.

I might be completely off on the purpose and operation of the NFB helm, though.
 
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