How to reduce rudder trim on 2004 ProStar 190 - parts are mated with a preset minimum trim angle

[swbca]

When loosening the set screws, the tab moves around, but when tightening, the tab forcibly returns to its original setting . . cannot be changed to a reduced amount of steering bias. It would require a shim on left side to reduce bias.

[Mastercrafter]

Likely indentations on the shaft from where it’s been tightened. Can you either take it out and clean on the burrs, or get it snug and tap the trim tab with a plastic mallet, to roll the sharp edges over?

[MNshortliner]

Possibly change the set screw to a different style? If it has a pointy end get a blunt end one or file it down. Or if it is a blunt one get a pointed set screw.

[swbca]

The trim has an adjustable range but has an end stop that prevents it from going closer than about 15 degrees from straight. The boat came set at that end stop and it has more bias than we prefer. Want to try a setting less than the factory end stop of 15 degrees.

 

15 degrees is just a guestimate to illustrate the issue.

[DW]

Maybe the shaft can be rotated to move the burr/indentation around to it doesn't force the tab to where you don't want it. Maybe the tab could be flipped upside down thus moving the set screw. If all fails, you simply have a ski muscle building steering torque:-)

Question, given the timing of the question, did your tab experiment change or increase the steering torque, just curious.

[swbca]

@DW I never changed the trim. It was preset at the straightest setting possible. The end stop at about 15 degrees is caused by a designed limit when the large mating surfaces of the rudder and tab are pulled together by the set screws. No rotation beyond 15 degrees from straight is possible. Larger angles can be set with no interference from set screw indentations. The only way to straighten the angle some increment would be a metal shim on the left.

[DW]

@swbca - just as a comparative data point, although I don’t know the exact setting or if a grind was done, a friends MC PS197 has a lot of rudder torque. May have no relation but thought I’d share.

[BraceMaker]

Is your rudder the "z-marine" style?

 

If so I thought it was more of a side to side shift than an angular change?

[Andre]

@swbca Post a pix.

2004 had the old style rudder that change in 2006.Some older boats have been retrofit with the newer style rudder.

A pic is worth ...what it's worth!!! :)

[swbca]

The picture shows the right face of the trim-tab is straight with the rudder, and the left face has an angle. When loosening the set screws the tab moves around, but when tightening the set screws it won't seat in a position that reduces the angle. I think a shim on the left side would do it, but I will try that to make sure.

 

 

[BraceMaker]

What about flipping it upside down that should switch the angle and give you proof of concept.

[igkya]

Replacing the lock washers fixed our problem, but we have a Nautique :D

[LeonL]

This is a 2004 MC on our lake. Why a difference between @swbca boat and this one? Which is correct for 2004 MC, or was there a mid year change?

 

[swbca]

I have a 197TT. The winged rudder was discontinued on the 190/197 TT model in 2002.

[swbca]

@bracemaker It could be flipped upside down, but the bolts aren't positioned vertically for this. The tab would be sticking down a inch below the rudder and the angle would be fixed but in the opposite direction.

 

I experimented to see of a shim would work. I would work but it would have to be made but what thickness ??? . Don't know if I will get to that.

 

I could grind down rudder mating surface, to change the fixed angle, but how much ??

 

Maybe I will look at a different rudder sometime.

[LeonL]

So, the winged one pictured above is not correct for a 2004? I think it's a 190, but don't know about any suffix.

[SkiBadger]

@LeonL - I have the winged rudder on my 2002 PS 190, and a buddy has the same rudder on his 2001 PS 190. If my memory is correct, MC in 2004 added the 'hook' to the hull and removed the wing for the PS 190 and 197. FWIW, I bought my boat in '05, previous owner had the hook added to the gelcoat and cut off the wings. To improve the wake, I added the winged rudder and it made a noticable improvement.

I have not seen a MC rudder with the tab in the pic posted by @swbca on a PS. I thought all fine tuning was done with a grinder. :)

[swbca]

The winger rudder was discontiued on the 190 and 197 TT promo boats in 2002.

[JTBMD]

If my memory serves me correctly the “winged” rudder was the “fix” for 2001-2002’s hulls due to problems with chine lock.

[swbca]

Some dates corrected from other posts . . In 2002, the 190/197 Tournament Team (TT) boats were intriduced which feature a slightly different hull design. A hook was added behind the rudder where the hull met the transom. The hook serves to level the boat, softening the wake and improving tracking. The winged rudder was also discontinued on the 2002 190/197 TT boats.

[Drago]

@swbca , I think once you figure this out, you will find that boat needs that much preload

[swbca]

Issue resolved . . Reshaping the trim tab was the only way to change the preload. So I ground down the control surface of the tab to 1/2 of its original angle relative to the plane of the left side of the rudder. Its not enough preload for tricks but my driver prefers it at slalom speeds. It took 15 minutes on a bench wheel grinder. Now have to refine the work to make it look like it was made that way.