P factor, prop wash.

[dakno]

I have a 08 41ds with the Yanmar 4hj4 54hp. Boat came with a fixed 3 blade and I have since changed to a feathering prop. When motoring, The helm has
great force to port. This was the same with either prop. Has anyone else experienced this with the same boat, i.e.; 2004 -2012 H41 ac or ds? This boat would be unmanageable for long periods of time without auto pilot.

 

[Rick486]

I own a 2007 44DS 4JH4E 56 horsepower Yanmar. When powering there is considerable prop wash on the rudder which is felt through the wheel. Mine is not "unmanageable" however and I often steer when powering in any large seaway. I am not aware of a large force to port or starboard on my boat. It feels more like a vibration in the wheel. My shaft is angled slightly to port which would tend to push the bow to port. Also my prop is RH rotation which would also tend through prop walk to push the bow to port. Perhaps your boat, being very similar, may have these design features as well.

 

[SEMPERAVANTI41]

I have a 07 41 DS and have never noticed a pull to port while motoring. Upon initial acceleration from a stop, I do feel a pull to port which goes away once the boat reaches cruising speed. I would check the alignment of the shaft, perhaps it is off center to the center line of the boat.

 

[dakno]

Update, my 08 H41 pulls very hard to port when motoring with engine speed above 2000 rpm. I would love to hear from any 04-12 H41 owners regarding helm forces when motoring. Helm is balanced under sail, a bear under power. I had a 18x12, 3 blade fixed, then replaced with a feathering 3 blade MaxProp. the torque steer, helm pressure was the same with both props under power. Is this typical for this boat or is there something I should be looking at. I have the Myanmar 54hp, I am the 2nd owner of a lightly used low hour boat with no damage history. Other than the strong helm pressure all is good, no vibrations, etc. What gives?

 

[dakno]

Okay, my boat is in a boatyard now getting a new bottom and other maintenance . I will ask yard if they can check alignment. There is no drivetrain vibration as you would expect id alignment, was off. I will have a look

 

[JamesG161]

Check your motor mounts too.
The motor is pushed forward when at high RPM.
Also the cutlass bearing should be changed if you have to align the shaft.
____
You might see if the folding prop is NOT folding right or completely. One blade might be not fully extended when at high RPM. That would cause a improper thrust.

Good luck..
Jim...

 

[SG]

Is the feathering prop three bladed or double bladed? Did you change the pitch much or the diameter.
After you're done with checking-out the shaft/engine mounts (I doubt either would do that without a bunch of other things happening). Who's prop is it? Is the pitch adjustable?

Since you didn't notice this before, I suspect something is amiss with the prop: i) blades not deploying, ii) pitch being set wrong, or iii) you bought too large a diameter proper and are getting some weird flow.

That's my speculation. ;^)))

 

[Tom J]

P-Factor? Are you a pilot? Even with an aircraft, the p-factor is overcome by the rudder at increased airspeeds. Do you see this tendency to pull to port when you are sailing? If so, you are possibly looking at an alignment issue between keel and rudder.

 

[Davidasailor26]

I have a Beneteau 37 with a Yanmar 3YM30 which also tries to pull the wheel when motoring at cruising speed. I wouldn't call it "a bear', but you definitely need to keep a hand on the wheel or put the brake on. No pull at all when motoring more slowly or sailing. It's done this with both the OEM fixed 3 blade and Flex-o-fold 3 blade. I've just always attributed it to prop walk types of effects.

 

[jon hansen]

food for thought: to alignment the engine properly the vessel needs to be floating in the water, not up on the hard. flexing of the hull on the hard can be different. the alignment is to make sure that the engine is pointed straight with the shaft.
props spinning create TWO forces. 1: is the forward motion as the blades dig into the water to pull the boat ahead, like a screw. the prop wash is the byproduct of this action. 2: the prop pulls the boat to the side like a paddle wheel of the old stern wheeler's, 'prop walk'. the more aggressive the pitch the more paddle wheeling. the prop wash is turbulent and felt at the helm.
single engine planes engines are offset to correct this. IO's on motorboats have trim tabs to offset this. ,, and so on. twin engine boats spin the props oppositely to cancel the paddle wheeling effect from each other.

 

[RoyS]

Stand in front or behind boat while it is on stands and with your eyes only check to see if keel, prop, and rudder are aligned. My friend had a new Beneteau that was clearly not in alignment. May have been designed that way for all I know.

 

[Davidasailor26]

Stand in front or behind boat while it is on stands and with your eyes only check to see if keel, prop, and rudder are aligned. My friend had a new Beneteau that was clearly not in alignment. May have been designed that way for all I know.

Indeed. I was at the boat today and looked at the alignment, and the prop definitely is set off center.

It does seem to be deliberate - there is a joint along the bottom right down the middle of the hull, but it is sharply bent right just in front of the engine, and back to center just behind.

 

[Tom J]

The prop is definitely off center, but I can't see the being an issue once the boat is moving, and water is flowing around the rudder. I have seen some sailboats (Sabre?) where the prop shaft is set at an angle to clear the rudder. I motored my O'Day 23 with the outboard mounted to one side of the transom, and there wasn't any noticeable pull at speed.

 

[uncledom]

When I bought my boat it had a fixed three blade prop on the boat and a spare two blade in the lazarette. Traveling north on the ICW at dusk and just before a scheduled stop at Atlantic Yacht Basin, I hit a submerged log just as I was going under the Great Bridge Highway Bridge. It bent two out of three blades. That fixed three blade had considerable pull to port but nothing that cranking down on the wheel friction knob couldn't cure. Thankfully AYB swapped out the props for me. The two blade was much more efficient while sailing, gaining me half a knot. It had brutal prop walk, especially in reverse, when trying to dock but almost no pull when motoring. I researched props and decided on a Brunton AutoProp. It's pretty amazing in it's efficiency but especially it's almost complete lack of prop walk. I have a tendency to freak out line handlers when coming to dock because they never expect a sailboat to stop that fast. It's actually got the same thrust backwards as forward and I can get the boat to over seven knots backwards. That's A LOT of pressure on the rudder if it's even slightly off center. If you research it and decide to buy one do not get it from the A$$hats in CT, there is a really nice distributor in VA called King Propulsion. These props were originally developed for the landing craft like the ones on D-Day so that they had full thrust in reverse to get themselves off the beach. It is awesome for motor sailing, I can hit 7.5 knots @ 1400 RPM with a 6 knot wind.