You need to be MOVING BACKWARDS to offset prop walk and get the rudder to do anything.
Learn to use it to your advantage.
Go out and practice in open water.
Most folks creep way too slowly backwards because they're afraid of getting kicked sideways which is exactly what happens when you try to do it too slowly.
OTOH, you can use it to your advantage in making cool three point turns.
Like docking, practice.
Oh, I have a 3 blade, too. Have for 21 years.
You could also do a search on prop walk and read for weeks.
Practice is critical, but one little piece of advice helped me immensely. Be using the throttle, or steering the boat, but not both at the same time. Every boat is different, but mine would begin moving with just a big blast of throttle. So I would "blast" for a second or perhaps two, then reduce throttle to idle. Then I would steer with the rudder. If the boat slowed down so much that I lost steering, another short blast would put more way on.
As Stu said, go practice in open water. Drop a fender overboard for a visual reference. Two fenders lets you imagine a dock face. Four fenders describe the corners of a slip. If you are in water shallow enough to "attach" the fenders to the bottom using a weighted line, they will not move, which makes your practice more realistic. Plus, in open water, you can approach from all different directions, which lets you practice winds on the beam, the bow, the stern, and everything in between.
My Hunter walks to starboard, but no matter. I used it to simply back out of my slip and allow it to walk me to starboard all the way around the end of the docks giving me a perfect 3 point turn to head out of port. It provided the perfect arc to make it look like I actually knew what I was doing... I had 'um all fooled at the marina...
In other places where I had to be more thoughtful, I found that starting at an idle in reverse while being able to back out of somewhere controlling the prop walk easily by hand until the boat got some momentum and I could increase speed and have rudder control - don't overcompensate turning the rudder. There's a lot of inertia in getting a boat moving (or stopping).
Not sure how to explain it - I get the boat moving (with patience and rudder pointed in the right direction) then bring it up to enough speed to have good rudder control. I think Stu's term of assertiveness sums it up...
The above book really helped me out. I can't recommend it highly enough.
Stu's response is bang on. Get out in flat open water, pick a point on land behind your boat to point at. Stand in front of your wheel looking backwards. Power up to around 1500-1800 rpm and start steering the boat to that point. As the boat accelerates through 1.5 kts or so the stern kick to port will become correctable by the rudder as there is now enough water moving over it.
Once your tracking in reverse is mastered at speed. Practice the same thing, but this time practice starting speeding up to 3-5 kts and then stopping so you can see how the boat behaves. Try it with the wind from each side as well from the bow and stern.
Next get the boat doing 2-3 kts in reverse and then start practising 90' turns to each direction. Pick a point you want to turn to, and make sure that you roll out exactly where you want to. You'll likely overshoot or undershoot the turns initially but that is fine. The idea is to get comfortable turning the boat in reverse and seeing how the boat behaves going each direction. Try it at different speeds. If you've made it this far...finish with practice doing figure 8's in reverse.
A few hours of this practice will really boost your confidence and allow you to better plan a docking strategy in challenging winds and currents.
Hey Rugger, welcome to the forum. Unfortunately prop walk is just a fact of life. The angle of the shaft, the pitch of the propeller, and the direction of shaft rotation in reverse all determine how much and in which direction the stern will want to head. As Stu says, having enough way on so that there is sufficient water flow over the rudder is key to steering in reverse. My Hunter 37 Cutter with a two-blade prop does exactly the same as yours - the stern wants to go to port in reverse until the boat is moving fast enough for the rudder to become effective. Pre-planning, using prop walk and wind to your advantage, and practice, practice, practice will win the day. Good luck. And you have a great boat BTW.
@rugger. Welcome to the forum.
Prop walk is a feature of most props on boats. Sailors learn to use this as a tool. Each boat design has a little bit of difference in effect. The design features - Keel, Rudder, hull shape, prop size, prop design, prop pitch. - all combine to give you the amount of prop walk you are experiencing.
You can change some of these design elements and modify the amount of prop walk you experience. Namely the prop, but not the others, unless you get a different boat.
Here are are pictures of two props. One is more efficient and contributes less prop walk.
Prop walk to port pulls me away from the finger and into my slip neighbor so I learned some time ago to leave the stern line looped over the cleat and into my hand at the wheel to simply manage the amount of left to right movement as she starts to move. Once moving, the rudder takes over and I can steer as needed while I reel in the stern line.
Works great for me.
I discovered many years ago to ( if possible) back into a slip. Since once water is over the rudder I can control the boat and easily stop reward movement with a quick shot of forward. Leaving the slip, it's forward and almost immediate control.....An added benefit to backing in.... wakes are greeted by a cut water bow and not a blunt trasnsom..
I also have a Brunton's autoprop. And while it is expensive it's impressiveness outweighs the cost. Faster in forward and reverse. Minimal drag under sail. The best motor sailing you will ever experience as the blade self pitches constantly to provide consistent thrust at any speed. Many days when the wind is light 5 to 8 knots I can hit hull speed with the main sail up and the revs below 1400RPM. As far as I'm concerned it pays me back every day through fuel savings. Oh and I have very minimal port prop walk. The boat originally had a three blade, could only make 6.5 knots sailing on the best of days. Put on a two blade and motor performance, especially backing suffered. You really need to plan your maneuvers and drive much slower when docking. Prop walk was reduced. Sailing speed when up to around 7.2. Autoprop cured everything with a sailing speed of 8.2, reverse speed can hit close to the same but the boat is hard to handle and the rudder, not really being built for reverse, wants to pull out of your hand if it's off center. Backing at three knots is child's play with it. I can stop the boat dead from full forward in less than two boat lengths. That's some aft thrust. This prop was designed and used to get landing craft off the beach, it has full thrust in reverse and almost no walk. I know sailors are frugal but this is the best 4G I spent on the boat.
You are getting great advice. Midnight Sun has always had a two blade folding Martec. It does no really matter what you spin, props are only a way to apply horsepower to do something. three blades give you more instant gratification, but props are matched to engines. Back to propwalk. It is a fact of life. Used to your advantage, it makes you look like a genius. Not used, it makes you look like a powerboater. (A kinder term than idiot) The only way you will ever back to starboard is to get the boat going fast enough f or the rudder to overpower the torque of the prop.