driving-tips by river111

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HOLD ON—CHINE WALK MAY NOT GO AWAY




QUESTION: I have a 1997 Four Winns U17 Unlimited (looks like a Donzi Sweet 16 or Classic
18). The boat is kind of rare because they were only made for a couple of years.

The motor is now a small-block Chevy 383 stroker that produces 417 horsepower (a real
number). The drive is a Volvo SX (single prop). At around 70 to 72 mph, the boat chine walks so
bad I can't go any faster. There is still a lot of throttle left.

I have changed to a four-blade propeller and it helped some, but I've heard that trim tabs may
help. I would love to eliminate the chine walking. Any help you can provide would be great. I
know this is a smaller boat than you normally deal with, but you are "the man" when it comes to
boat setup!

ANSWER: Four Winns makes a nice line of family orientated runabouts and cruisers, but the
U17 is known to have a chine-walking problem, especially at high speeds. The hull has a
rounded keel and does not track well at high speeds. I believe that one of the reasons the boat
went out of production was because of its handling characteristics.

I do not believe that you will be able to eliminate the chine-walk condition completely without
some significant bottom modifications. Sometimes, propeller changes can help a little as you
have already found out. It is also important that your steering system is rock solid to minimize
stern-drive wobble, which can start and perpetuate a chine-walk condition. The only way to
insure that your steering is solid is to convert it to a full hydraulic system including a hydraulic
helm.

The single, most effective improvement you can make is to add trim tabs. On your Four Winns, I
would install them on the transom more horizontal rather than the traditional manner of being on
the same angle as the bottom.

When the trim tabs or planes are installed on boats with rounded keels in the traditional manner,
the affect could be that it makes the situation worse. When the tabs are mounted horizontally,
the outside edge of the plane contacts the water first, which helps to stabilize the chine walking.
With the tabs mounted on the traditional angle, the entire plane surface contacts the water at
the same time, which may have enough force to pitch the hull to the other side, and the
chine-walk condition is perpetuated.




—Need some guidance from Bob Teague, Powerboat's lead test driver and owner of Teague
Custom Marine



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