# Prop walk with a Max Prop



## TSOJOURNER (Dec 16, 1999)

I recently purchased a Max Prop for my ketch and am still experiencing substantial prop walk. I bought it mostly for the improved speed while under sail but was expecting a decrease in prop walk as well. Has anyone else had this experience? If so, was there a solution?

thx
Ike


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## TSOJOURNER (Dec 16, 1999)

Don''t know what your problem coould be. I went from a 36'' boat with a folding prop to a 43 with a 3 blade MaxProp and there was a huge reduction in prop walk. I back the 43'' into places I would never have dreamed of trying with the 36''. The only thing I can think of is that you might be overpitched. I also developed the the habit with the 36'' of giving the throttle a good shot of reverse to get the boat moving and then backing off after it starts to move. I do this with the MaxProp and it works beautifully.


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## TSOJOURNER (Dec 16, 1999)

I''m confused also, I went from a 3 blade fixed to a MaxProp (at a considerable premium) and expected to see some change but no luck. Thanks for advice (gun n'' coast) have tried it as I used to do with fixed blade but she is really walking before I''m making sternway. re: pitch, based on the boat''s performance in forward I am underpitched and need to increase it (PYI concurs with this assessment). Still confused but will have to re-assess after pitch change.

Thanks for the advice sailmc.


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## jack_patricia (May 20, 2001)

Ikent, what performance improvement did you find under sail with your Max Prop? (Did you measure this in a controlled enough fashion to feel some certainty with the measurements?) And who are you working with at PYI - Frederick? How''s the after-sales support you''re getting?

I ask because you''re ahead of me but I may be following the same path. Thanks!

Jack


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## TSOJOURNER (Dec 16, 1999)

I''m confused. What ever happened to recognizing the characteristics of your vessel and using them to your advantage?
Sailorat50


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## windship (May 4, 2002)

Are you getting proper rpm''s? Does your engine smoke eccessivly since the change? Can you have a different pitch in reverse? Is the angle of your prop shaft at an extreme angle to where the prop wash is forced up against the underbody?

Dennis


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## EscapeArtist (Jun 7, 2001)

I love prop walk. It lets me manuever the boat in ways that I could never duplicate if it were significantly reduced.

For example, most single-screw boats will turn left inside their own length, because of prop walk effect.

Rather than spending two thousand bucks on a propeller, Drop $20 for Chapman''s and read the section on boat handling under power. Make it work for you.


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## svindigo (Sep 11, 2002)

Thanks all for the responses - Please note I didn''t say I couldn''t manuever. I do work with the characteristics of the boat. I am seeking to understand why the more common experience of reduced prop walk with this prop was missing in my case. To answer a few of the questions, my pitch is the same in forward and reverse although PYI suggested that they could remachine the hub to give differing pitches. We''re not going down that road because I can maneuver the boat just fine. The angle in relation to the underbody is not extreme but my shaft resides in an underbody fairing that could be causing the "push". Sailing performance has been enhanced relative to the old fixed blade prop by about .5-.75 knots by our notes when sailing in 12-18 knots depending on point of sail. PYI service has been exemplary and I have worked with both Frederick and Kevin. They are both valuable sources of information. 

Thx
Ike


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## RichH (Jul 10, 2000)

Prop walk has as much to do with tip clearance from the prop to the hull, and the hull configuration (shape of aperture, skeg. etc.) where the prop wash impinges.
So if you want to reduce prop walk, consider to reduce the diameter of the prop and change the pitch. If you can master ''backing and filling'' when going astern .... you''ll eventually actually desire MORE propwalk.


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## awaghorne (Nov 10, 2009)

*Prop*

I noticed a mention of excessive smoking when discussing the props. I have a s/v Gulfstar 36 with a prop that has no markings. At the higher end of the RPM range I get backwash on my transom of un burned fuel. At about three quarter RPM very little is on the transom.

My mechanic says no problem run the engine. Tired of cleaning my rear end.

Am I missed proped?

Thanks in advance.


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## Cptken (Apr 23, 2008)

All props have prop walk in both forward and reverse. It cannot be avoided. It is not noticable when moving forward because the prop wash makes the rudder effective with even no way on. In reverse, this doesn't happen until the boat has enough motion to make the rudder work. As Rich said, tip clearance and boat design also play a big part.
Awaghorne: If you can make max rpms when in gear then you are not overpropped. Smoke at high power and unburned fuel could also be a sign of dirty/worn out injectors or a fouled prop


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## capecodda (Oct 6, 2009)

For what its worth, I've got a Maxprop in an aperture (skeg hung rudder). I get lots of walk in reverse. I didn't know the Maxprop was supposed to impact this.

To counter (for example if I need to back out straight from a narrow slip), I find cutting the wheel to counter the walk, and reversing aggressively until the rudder starts to "catch" allows me to back out straight. As soon as the rudder catches, I straighten it quickly before I start going the other way. Other times the walk can be useful. YMMV.


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## btrayfors (Aug 25, 2006)

I've had a three-blade Max Prop for 21 years. Replaced a 3-blade fixed prop after a trip down the waterway from Annapolis to Ft. Lauderdale. 

I immediately noticed:

1. no benefit in forward under power;
2. big benefit in reverse under power...the MaxProp made backing much more efficient; and
3. no decrease in prop walk compared to the 3-blade fixed prop.

Have thousands of inland and sea miles on this prop now. Love it. Absolutely reliable. The better performance in reverse allows maneuvering you just couldn't do with a fixed prop.

Bill


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## jfdubu (Jul 18, 2002)

Prop walk is as much a charactoristic of the boat's hull, shaft angle, prop to rudder,prop to hull clearance as anything else. I can't understand how the prop guys can sell you on reduced prop walk with thier prop unless they significantly change the prop dia.
Bottom line, the prop is designed to produce thrust forces forward and reverse. In the process they also generate torque on the boat. some prop designs may change the torque some but not much. It's how a boat handles the torque that shows up as prop walk.


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## Minnewaska (Feb 21, 2010)

As the thread was resurrected by awaghorne to ask about fuel/soot on the transom, I doubt that has anything to do with the prop. It could be many other things, but not enough info to know.

As far as Max-Prop prop walk, I get a fair amount to port when initially powering into reverse, but it calms down when the rudder become effective. Reducing drag under sail is the only reason I care about the feathering prop.


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## blt2ski (May 5, 2005)

Had out prop/tranny in N for tonights sail, finally on the downwind leg I kept noticing a hum the did not sound correct........prop was turning! put in reverse, gained 1/4-1/2 knot after the prop quit turning!

I do have a bit of prop walk to port, but if I am coasting, then idle the prop in R initially, then there is not as much prop walk. 

marty


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## mitiempo (Sep 19, 2008)

In a full keel boat with the prop in an aperture or a boat with the prop in an aperture in a skeg attached to the rudder the prop acts a bit like a thruster, pushing water sideways out of the aperture. You need speed in reverse to overcome this before the boat answers the rudder direction.


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## erps (Aug 2, 2006)

> As far as Max-Prop prop walk, I get a fair amount to port when initially powering into reverse, but it calms down when the rudder become effective. Reducing drag under sail is the only reason I care about the feathering prop.


Our previous boat had a fixed three blade prop and had a lot of prop walk. Our current boat came with a maxi prop and the prop walk is nearly undetectable. It has a long fin keel and skeg hung rudder though, so I don't know whether it's the boat's bottom or the prop. I've heard several times that maxi props don't have much prop walk and thought that was the case with our boat, but it may have been a premature conclusion. Faster just put a maxi on his boat, so he may be able to shed some light on the matter.


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## Faster (Sep 13, 2005)

We have just gone from a 2 blade fixed prop to a 3 blade MAX. The improvement in smoothness and reduced vibration under power is considerable. It seems to me so far that there's less prop walk initially than we had with the old fixed prop, but our boat has always tracked well in reverse so the difference is not a big deal (in actuality I made good use of the prop walk we had, and may even miss it if it proves to be 'gone'.)

The bite and improvement in getting the boat moving in reverse is remarkable. The fact that the prop blades are not working backwards would, I imagine, explain this. Overall I'm very pleased but haven't had a lot of sailing weather to try out and quantify the reduction in drag under sail yet.


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## Faster (Sep 13, 2005)

Further to previous post:

This weekend we've finally had a good try at sailing with this prop and the performance gain has been terrific. Really pleased.

As to the prop walk, it's still there but the boat starts moving aft so much earlier that the overall effect is reduced as the rudder takes over sooner.

The three blade smoothness under power is also a treat, as is the lack of feeling the swirl off the locked fixed blade on the rudder when sailing.


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