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1999 Four Winns Horizon 180 BR with 130 HP Johnson Ocean Pro OB.

​As the title suggests, my boat has developed a marked list to port. When I say developed, I mean we've had the boat a year now and it didn't have the list before. The only thing I changed was the prop but that was when I first bought the boat.
Last night we took it out: the were 5 of us in the boat. I had the three men sit on the starboard side and the 2 women (significantly lighter) sit on the port side. The boat still listed to port to the point where it became unnerving when making a tight left turn.
At one point I let go of the steering wheel (at high speed) and it whipped to the right so fast I thought I was going to flip the boat. I'm constantly "steering" left when at speed but it seems to track perfectly when running slowly.
Could the torque tab be the problem? (it is angled slightly left now) I'm hesitant to put trim tabs on such a small, basic, boat. If I were to do so, do they affect performance much?
I've removed the drain plug several times and absolutely no water has come out. Is it possible to have water trapped somewhere that doesn't get to the drain?

Any suggestions would be greatly appreciated.

You say the boat listed to Port. Is this only while on plane, or does it list to Port at idle and while just floating? Does the boat have an added fin (Stingray, Edge, Whaletail, etc) on the anti-ventilation plate? Was the outboard motor trimmed up or still all the way down?

The addition of a fin and/or full down trim usually causes the boat to list to port while cruising on plane. The faster you go the more the boat wants to list to port. This is because full down trim, and especially with an added fin, tries to lift the rear of the boat more than the water is supporting, and forces the bow into the water. This stern "lift" and the torque of the prop causes the boat to list to port. This is kind of like a wheelbarrow and you are lifting more with your right arm.

You also commented that you let go of the wheel and it whipped to the right so fast you thought you would flip the boat. This also indicates that you had the motor trimmed full down. Without a power steering system, the steering wheel will pull to the right with full down trim. The wheel will also pull to the left with the motor trimmed up too much. In between the two extremes is a point where the steering wheel does not pull either way. Consider the angle of the prop shaft to the flow of water past it. With full down trim the prop blade(s) on the right side are going down and taking a larger bite than the blades going up on the left side. As you trim the motor up this difference between the prop shaft angle to the water flowing past it is reduced, then neutral, then increased when the motor is trimmed up even further. This difference from one side to the other on the prop is what causes the boat to want to steer to the right when trimmed down, and want to steer to the left when trimmed up.

One solution is to trim the motor up after getting on plane. This lifts the bow, the boat levels out, the steering wheel does not pull to the right, and you get more speed. Adjust the motor's trim for reasonably comfortable steering. This may vary with different speeds.

As you stand behind the boat, the trailing edge of the trim tab should be toward the right side.

Hope this helps.

_________________
Surface Interval: A scuba diving term for that time between dives to relax and prepare for life's next great adventure.

Current boat: '02 FW 268 Vista
Previous boat: '95 FW 190 Horizon

Surface Interval's reply is very good. I agree that it is very important to know if this is happening only on a plane, versus how the boat sits in the water with no power. A few comments to add:

Yes, there is definitely places where water can hide that will not drain out the bilge. (It's not supposed to get under the floor, but it IS possible) If you are heavy on the PORT side, that would want to cause the boat to want to turn left, not right.

The Trim Tab being angled to the left, would make the boat want to turn right... The "left" tab would push the BACK of the drive to the right, which would be a right turn. But the "slightly left" tab does not sound like enough to match the hard-right steering you described...I would lean towards Surface Interval's explanation of tilt/trim angle.

If you have water under your floor on the PORT side, it could also be extreme AFT or FORWARD, which could lead you to trim in an unusual way. How does the boat sit (in the water) with no passengers? (seems like it would need to be hundreds of pounds of water to cause your symptoms, so weight alone does not seem like a likely explanation)

Is there any damage/twist to your skeg?
Can we assume you have looked at the bottom of your hull for damage? A serious crack in the bottom of the hull (port side) could allow water into the enclosed space under the floor which does not necessarily drain to the bilge.

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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings