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rslifkin · 04-04-2021, 06:54

Even with hydro transmissions it's a good idea to pause in neutral for a second unless it's a real emergency. Although some of the heavy duty commercial marine hydro transmissions are designed to handle a forward -> reverse shift with the engine at WOT for a crash stop...

But in general, hydro transmissions are much nicer and more tolerant when maneuvering. Any time I'm on a sailboat with a mechanical trans, I always feel like shifting the thing is a bit of an exercise in "am I going to break something today?" It's a great contrast to the hydro transmissions in my boat (Velvet Drives in my case) that I'll happily bump in and out of gear without a second thought.

Talbot · 09-04-2021, 06:34

Different props have different characteristics. Prop walk can be useful for an alongside, but can also make things more difficult if you are constrained by wind and tide.

Some props seem to minimise the problem, and brunton's autoprop on my boat certainly does not have any problems.

Prop walk in a crowded marina is not for the faint hearted.

lo2jones · 09-04-2021, 07:27

When backing out of the slip, try putting it in reverse for 2-3 seconds, then casting off lines. One of the boats I skipper has wicked port prop walk. This technique helps me get out of the slip without bumping into the boats in the next slips.

Also, hull shape can magnify prop walk, so changing the prop may not do much. Talk to your fellow owners through a users forum first.

rslifkin · 09-04-2021, 07:31

Quote:

Originally Posted by lo2jones

When backing out of the slip, try putting it in reverse for 2-3 seconds, then casting off lines. One of the boats I skipper has wicked port prop walk. This technique helps me get out of the slip without bumping into the boats in the next slips.

Also, hull shape can magnify prop walk, so changing the prop may not do much. Talk to your fellow owners through a users forum first.

Along those lines, if the stern walks away from the dock, you can let the bow loose first, pull the stern tight against the dock and then put it in reverse. The prop walk will serve to straighten the boat out in that case and you should be part way out of the slip and have a little steering before the stern gets too far over (or the bow gets pulled into the dock).

GrowleyMonster · 09-04-2021, 08:08

I won't add to the possibly confusing menu of ways to mitigate or to take advantage of side force, the actual proper term for "prop walk", but it should be obvious to the OP by now that there are ways of dealing with it and living with it. As for the question of whether a two blade or a three blade prop exhibits this tendency more strongly, the number of blades is not as important as other factors, all other things being the same. Yes, a three blade prop WITH THE EXACT SAME BLADES, PITCH, ETC will pull the boat's stern more strongly to the side. However, switching to three blades usually doesn't work that way. To keep the same engine load profile, you might go with shorter blades, or lower pitch, for instance. And this would change the equation. I'm sure there are plenty of clever engineers who can calculate all this, but good old Redneck "try it and see" is pretty dependable, and almost anybody can do it. Most prop shops have old wheels laying around that you can borrow or buy with option to sell back, an if you can change them out without hauling out, you can find a configuration that suits you. But one of the biggest factors in how strongly a boat backs to one side or the other is one that is not part of the prop. It is the down angle of the prop shaft. You can visualize how this works by considering in your head a shaft that is level and one that is nearly straight down. In reality you would probably not have the former and would of course definitely not have the latter. But remembering that every action has an opposite but equal reaction, you can see how a flatter entry angle gives the strongest lateral force, while a pronounced down angle gives less of this effect, eventually at an impossibly high angle reaching the point where side force is zero and if taking this still further, in the opposite direction. There are of course good reasons to not have a prop shaft that points down at a 45 degree angle. But even at more modest, real world angles, a difference in a couple of degrees will be significant.

Hull clearance is another big factor. As well as the depth in the water of the prop. But blade area, blade length, and pitch are all sort of portable. Change the prop, change those factors.

I have never seen a single screw boat that could NOT be maneuvered effectively. It's all about learning to adapt to the boat and not expecting the boat to adapt to you or suddenly start doing the right thing.

Riggerman · 09-04-2021, 08:11

The answer is yes, definitely yes. But prop walk can be a useful tool once you know hoe to control it. I can spin My 43ft on a dime with proper amount of reverse and forward trust without even turning the wheel.

captainwd40 · 09-04-2021, 08:41

3 is better than 2 and 4 is better than 3 when comes to spinning things and the laws of physics

Dr. D · 09-04-2021, 08:41

My boat has neither prop walk nor prop wash. I am pleased.

SV__Grace · 09-04-2021, 08:43

I used to hate prop walk but now I love it.

BTW- of the 9 or so keel boats I've owned in the past 35 years, the 30 footer with sail drive was the worst and would immediately kick 90 degrees to port in reverse, the most awful prop walk of them all.

The reason I've learned to love my prop walk is because I love older boats and our current one is 1985 Nauticat 43, a 20 ton cruising ketch.

Older boats don't come with thrusters, so dealing with prop walk is a fact of life.

Most U.S. boats have right hand rotating drives (clockwise, facing forward), which means Port prop walk (reverse) and Starboard prop wash (forward).

The hardest, scariest thing about a big, heavy boat like ours is navigating in close quarters in a marina, which is where prop walk is your friend, because-

1. You can do a 360 degree turn within a boat length, very handy in a narrow fairway. Whenever I got "lazy" and tried a tight turn opposite prop walk, I always regretted it, so in a tight fairway I always turn to Starboard even if it's the long way around. Keep your rudder to Starboard and use short bursts of minimal power alternating forward and reverse and your patience will be rewarded. You should be coasting in neutral more than "powering" in the turn. Do this slowly for maximum control.

2. You can crab sideways without thrusters. This only works in the direction of prop walk, so I almost always will choose to dock on the Port side, especially at fuel docks. Keep your rudder to Port and alternate short bursts forward and reverse. Reverse, of course, will swing your stern to Port, and forward will swing your bow to port, so just be patient and keep going until you reach the dock (or buoy). As above, use thrust only to get the bow or stern moving and coast in neutral as much as possible for maximum control.

3. Backing up in reverse, as others have mentioned, requires using a burst of power to get moving, then neutral as you move backwards, correcting with forward bursts as needed (you can do this without going forward) repeating this until you're where you want to be. As above, patience and practice is all that's needed.

These skills require practice and mastering the ability to maneuver your boat is how you earn your stripes as a skipper. You can stop lusting after newer boats with thrusters and impress the weekenders and old salts alike with a bit of patience.

[Please note that the directions above are opposite for left hand/counter clockwise drives.]

skenn_ie · 09-04-2021, 08:55

A boat from my childhood had a turning circle of about 80m to Stbd, and and 15m to Port. She was small enough to pull backwards, but reverse was directionally uncontrollable.

Lazy Jack 32 · 09-04-2021, 09:03

Yes, and here is some proof. My brother and I own identical 32' boats, his with a 2-blade and mine with a 3-blade prop. You can reverse his in a straight line with a little help from the helm. Mine, helm be damned, will go 45 degrees to port.

SeaRaider · 09-04-2021, 10:06

I have a Hunter 380. Fixed 3 blade gave me big time prop walk. I went with a Flexofold 3 blade prop. I can back to port or SB anytime easily. No fancy throttle gymnastics reqd. Here is why. I suspect that in reverse with low engine power, the prop does not fully deploy (keeping p-walk near zero). The prop holds a low diameter cone shape at low rpm's in reverse and it pulls you aft in a straight line. I am sure this will solve your problem.