correcting prop torque without trim tabs?

[2rz-fte]

is this even possible?

i have severe prop torque issues, my boat leans left hard under power. my props outer edge isnt perfect (could this be adding to the issue?)

but i keep reading that to combat the prop torque you just trim the lower side down a little to balance things out. i also read that a 4 blade prop will have less drag onthe water and have less prop torque.

trim tabs are not an option for me... yet.

i have a 16' bowrider with a 'rude 88 and i max out at 35mph.

 

[Chris1956]

Re: correcting prop torque without trim tabs?

Does the steering wheel also pull left or right? If so, most OBs have some kind of fin just above and behind the prop. These are adjustable to counteract some of the steering torque. On Mercs they are made of zinc. My Johnny has one made of aluminum. Turn it in the direction of the steering wheel pull and see what happens.

If the boat still leans, you may have a problem in the hull. The hull could be untrue.

Does the motor have PTT or is the tilt pin in the second transom bracket hole? Trim the motor up a bit and see if it helps.

 

[2rz-fte]

Re: correcting prop torque without trim tabs?

i have no feed back steering so my wheel doesnt pull.

i do have power tilt/trim.

i also do have that little fin thing youre talking about (red arrow). i can try to mess with that. i doubt my hull is un-true, because in flat water its fine, but if im in swells and the bow is rising and falling, as it rises its lean left unless i throttle down.

as i said before my prop isnt in "brand new" condition (cyan arrow). can this cause this issue as well from the prop baldes having too much friction?

 

[seabob4]

Re: correcting prop torque without trim tabs?

Set the trailing edge of the torque tab to between 1:00 and 2:00. This should help your issues...

 

[2rz-fte]

Re: correcting prop torque without trim tabs?

Set the trailing edge of the torque tab to between 1:00 and 2:00. This should help your issues...

this goes against everything ive been reading. i thought trailing edge is supposed to go in the direction of the lean/list.

since im listing port, the trailing edge should be more of a 11 o'clock position.

i found this picture online, mine should be similar. no?

 

[rockyrude]

Re: correcting prop torque without trim tabs?

The idea of that tab is to fight the torque steer, if it steers port you adjust starboard to bring 'er back to center.

 

[seabob4]

Re: correcting prop torque without trim tabs?

Try it, you might like it...

On a center console single, where the weight of the helm and driver is centered, 1:00 works good. On a side console, where that same weight is shifted to starboard, 1:30 to 2:00 is the ticket...

 

[2rz-fte]

Re: correcting prop torque without trim tabs?

The idea of that tab is to fight the torque steer, if it steers port you adjust starboard to bring 'er back to center.

also what ive been reading is the "trim fin" does not operate like a rudder. if this is true then adjusting i to the opposite side of the list wrong.

if i list to port, do i adjust the fin to port as well?

 

[gozierdt]

Re: correcting prop torque without trim tabs?

Think about the forces of the water on the tab. If the tab is turned to 11, as in the picture you showed, the water hits on the port side of the tab. That's going to create a force pushing to starboard on the tab. That's going to rotate the boat counterclockwise (looking from the stern forward), increasing any lean to port you have. If you turn the tab to 1 pm (again going with the picture you showed), the force on the bottom of the drive is to the port, which tends to rotate the boat back to starboard.

 

[Rocky_Road]

Re: correcting prop torque without trim tabs?

Think about the forces of the water on the tab. If the tab is turned to 11, as in the picture you showed, the water hits on the port side of the tab. That's going to create a force pushing to starboard on the tab. That's going to rotate the boat counterclockwise (looking from the stern forward), increasing any lean to port you have. If you turn the tab to 1 pm (again going with the picture you showed), the force on the bottom of the drive is to the port, which tends to rotate the boat back to starboard.

Just the opposite...the trim tab forces the outdrive to go the other way, and the boat responds in the opposite direction.

Besides...he is talking about his boat "listing", not torque steering.

Let's hear back from him as to whether he is having a listing issue, or a torque steer issue.

For what it's worth...I have never seen an I/O trim tab that wasn't in the 11:00 (or close to) position. Torque steering dictates that the outdrive be 'forced' into a starboard inclination.

Happy boating!

 

[2rz-fte]

Re: correcting prop torque without trim tabs?

i have a listing issue that is caused by my prop torque.

what gozierdt said makes sense if the trim fin functions as a rudder. but from what i have read, it DOES NOT FUNCTION AS A RUDDER.

rocky_rode, i have an outboard if that makes a difference. (i dont think it does)

 

[Rocky_Road]

Re: correcting prop torque without trim tabs?

i have a listing issue that is caused by my prop torque.

what gozierdt said makes sense if the trim fin functions as a rudder. but from what i have read, it DOES NOT FUNCTION AS A RUDDER.

rocky_rode, i have an outboard if that makes a difference. (i dont think it does)

You are right: it is only a "rudder" for the outdrive, which forces the outdrive to go in the opposite direction. This forces the steering torque (felt at the helm) to be the opposite.

Most I/O driven boats want to go port (left) when you release the wheel...and you have to apply constant right hand correction to overcome this. The trim tab is turned trailing edge to the port (11:00 for reference only) to force the outdrive to want to turn starboard. This equalizes the so-called torque steer....

If your boat is listing, then the lower unit trim tab is not your answer. We may be confusing a true list with torque steer....

An outboard is still hinged on the transom for physics purposes, just like the outdrive of a I/O. The function of an outdrive trim tab will be the same.

If you are talking about hull trim tabs, then you are in a different conversation...and they will correct a boat 'listing' issue.

Happy boating!

 

[2rz-fte]

Re: correcting prop torque without trim tabs?

im a little confused by your replies but this is what i know from the posts so far.

if the boat lists/leans/pulls to port, adjust the trim fin's trailing to port as well. hence 11 o'clock.

 

[Rocky_Road]

Re: correcting prop torque without trim tabs?

im a little confused by your replies but this is what i know from the posts so far.

if the boat lists/leans/pulls to port, adjust the trim fin's trailing to port as well. hence 11 o'clock.

Sorry for any confusion!

If you are "pulling" to port...then the trailing edge of the outdrive tab is also put to port. This is almost always the case (pulling port), and I think that we are on the same page!

Give this a shot, and tell us what you find!

Happy boating!

 

[PWH1]

Re: correcting prop torque without trim tabs?

I have a 16' foot open bow with a 90 Johnson. I was experiencing torque steer going towards starboard. I make a slight tab adjustment towards 1 o'clock and the next time out the condition was all but eliminated. The boat steered much easier at speed.

 

[Fed]

Re: correcting prop torque without trim tabs?

Well this is from someone who has full feedback steering & I know exactly what my boat is doing at all times.

It's natural for outboards to steer to the starboard because the crankshaft is turning clockwise which causes the block to try and turn anticlockwise. When running on the muffs my motor flicks to the starboard lock if I goose the throttle and in fact OMC motors have a starboard bias built into the little fin to counteract this.
So, the little fin is there to adjust steering bias only and has nothing to do with listing. Motor trim will also impact on steering bias.

It's natural for boats to list to the port because the prop is spinning clockwise which causes the whole hull to try to spin anticlockwise. (All when viewed from the rear)

So what resists this listing bias?
Weight placement and water pressure against the hull.

You should try and move some weight to the starboard side.

A good prop will convert more of these forces into forward movement instead of trying to spin the hull in the water.

 

[ibrw1]

Re: correcting prop torque without trim tabs?

Sorry for any confusion!

If you are "pulling" to port...then the trailing edge of the outdrive tab is also put to port. This is almost always the case (pulling port), and I think that we are on the same page!

Give this a shot, and tell us what you find!

Happy boating!

Trailing edge Port is 1 Oclock? No? and his prop rotation is Left had? Which is Uncommon?
These are questions from someone who just doesn't know. THANKS

 

[ttiger27]

Re: correcting prop torque without trim tabs?

If your boat is wanting to steer port(left) then you adjust your fin to the left, because when you do that it wants to force your outdrive to the right which in turn forces the boat to turn right. Remember it does not act like a rudder, what it does is acts as a rudder for your outdrive, not your boat. So when you turn your wheel to the right, it points your outdrive to the right which forces the rear of the boat to port(left) and in turn forces the boat to turn right. It is kina backwards until you think of it from the outdrive point of view instead of the boat point of view. Hope this helps.

 

[high'n'dry]

Re: correcting prop torque without trim tabs?

The trim tab on the lower unit is for torque steer. It is to be adjusted OPPOSITE of the steer to push the lower unit in the desired direction and to reduce steering effort to that side. It will have little to NO effect on the boat leaning as a result of propeller torque or imbalance. The ONLY way to correct this is to install trim tabs with a controllable switch. You can also shift your load about.

 

[guy74]

Re: correcting prop torque without trim tabs?

The only boat I have been around that listed while on plane had a bent skeg. The boat leaned to port at speed, until strightened the skeg, then the problem went away. Torque steer is caused by the fact that the bottom of the prop is in denser water than the top, thus creating more drag on the bottom. The bottom of the prop is traveling to port(on most motors), thus pushing the motor starboard and creating feedback trying to steer the boat to starboard.