Free wheel prop or lock it?

Mark F

Contributing Partner
Blogs Author
To add to Seth's excellent instructions on setting the shaft; if you have a two blade folding prop like a Martec lock it horizontally so you do not end up with a lower blade hanging down in light air.

Also make sure the prop shaft is stopped before grabbing it. It can be dark down there in the engine compartment. I have a friend that grabbed a shaft that he thought had stopped and it hadn't. He ended up going to the hospital and getting something like 20 stitches in his finger. He missed the race but made it back to the Harbor after the race for dinner :)
 

Seth

Sustaining Partner
yep..

Same procedure for setting the folding prop. Using the same steps, rotate it until the blades are horizontal, and mark the top of the shaft. The good news is you can do this without going in the water; with the tranny in neutral, rotate until you hear the clunk of a blade opening and falling down. Then rotate 90 degrees from this position and you have have the right spot!

Cheers,

S
 

Maine Sail

Member III
You will never hurt anything by leaving it in reverse.

Unless of course you own a Yanmar...;)

Advisory Number: MSA08-003:

DATE February 8, 2008 Dealers and OEMs
TO: All Marine Distributors
SUBJECT: Gear in Neutral While Sailing All MODELS:

All Sailboat Engines

We continue to get questions regarding the correct gear position while sailing with the engine OFF. This advisory is issued as a reminder; Yanmar requires that if sailing with the engine OFF (not running) the transmission shifter must be in the neutral position or internal damage to the gear or sail-drive will result. This damage will not be covered by Yanmar’s Limited Warranty. Please instruct customers and dealers who deliver the sailboat to the customer, of the correct (Neutral) position for the marine gear while sailing.

If the customer desires that the propeller shaft not spin while sailing, either a folding propeller, shaft break, or other suitable device may be used. However, Yanmar accepts no responsibility for the selection, installation, or operation of such devices. Please also refer to Marine service advisory “MSA07-001_Yanmar Sail Drive Propeller Selection” for additional information.

If you have any questions regarding this advisory please contact a Customer Support representative.

Yanmar Prop Position MSA (LINK)

The guy from Yanmar admitted that prior to 2008 they did not take much of a position either way in regards to reverse or neutral, hence the constant confusion on the forums when talking about Yanmar's.

This info does NOT apply to other engine makers.

For sure, I believe that with a 2 blade fixed prop locked in a vertical position you will have less drag than you would with it spinning.

You would not be the first to still be a disbeliever despite the data to the contrary, many still do. I have also tested a 16" two blade, the same way, and it too has more drag locked then when allowed to freewheel. This was also duplicated about a hundred times on my old C-36 which had a fin keel with a fixed Michigan 2 blade. I always sailed faster or the same speed free spinning than I did when locked with the original factory Michigan Wheel 2 blade. I never once observed the two blade prop add any speed when I locked it. Same on our old Cape Dory but that slug was just difficult to observe any minutia of effect either way.

If you want to know which is more drag simply align it vertically and if it stays there, by itself, when put back in neutral, than it is not causing more drag. If it starts to spin it is taking the path of least resistance. We know that towing a fixed two blade or three blade through the water causes more drag when locked. On our Cape Dory 27 even when set vertically in the well protected aperture behind the full keel it would still want to spin when put back in neutral. This simply means it is NOT as hidden behind the keel wake as people often assume.


Having the blades straight up and down right behind the trailing edge of the keel should really reduce prop drag and enhance sailing performance.

Problem is on most Ericson's the prop is not "right behind the keel" it is set back quite a ways. If it spins after locking it vertically it is just taking the path of least resistance. I have never observed what you have and I have studied this at great lengths over many years in many different situations.

I have heard the research saying a spinning 3 blade is faster than a locked one, but it seems odd to me, and you can't hurt the tranny by leaving it reverse.

Again, unless you have a Yanmar. The Hurth's can be left in either neutral or locked, but free spinning will always result in some minor wear on the cutlass and potentially the gear box. These Hurth/ZF boxes are splash lubed so they get lubed whether the engine is running or not..

I will leave the 3 blade drag argument to smarter folks than me, but for a 2 blade fixed, locked and vertical is fastest and safest for the engine.

Old tales die hard deaths....;)

From The Strathclyde White Paper:

"The experimental results confirm that a locked propeller produces greater drag than does a freewheeling screw (up to 100% more drag was observed, this being at higher speeds). Furthermore, for the freewheeling case, the magnitude of the hydrodynamic resistance is significantly affected by the amount of frictional torque on the shaft, low torque being accompanied by low drag.

Finally, a simple model of sailboat hull resistance has been used to illustrate the likely scale of the drag penalty due to various arrangements of trailing propeller. This shows that, especially for the case of craft having moderate or low displacement-to-length ratios combined with powerful mechanical installations, the impact on sailing performance of a trailing propeller is very significant indeed. By combining the
present findings with other more detailed techniques which exist for modelling hull drag, the influence of propeller drag on sailing performance should be substantially predictable."
 
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tyrguy

Member II
So ?

My engine manufacturer(Westerbeke) says to not put into gear, the transmission manufacturer says you can put into reverse or neutral, the prop manufacturer(max-prop) says to leave in forward. ?????????

I just want to go sailing
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
My engine manufacturer(Westerbeke) says to not put into gear, the transmission manufacturer says you can put into reverse or neutral, the prop manufacturer(max-prop) says to leave in forward. ?????????
I just want to go sailing

What? go sailing? And miss out on the census constantly being conducted on threads like this regarded dancing angels on heads of pins!?:rolleyes:

Seriously, if you have a feathering prop, you do need to lock the shaft, at least when you initially start sailing. When the boat is moving forward under sail the water pressure against the blades will straighten them out. This might work even when in neutral, but I have found that the blades have some resistance to rotating in their hub due to the stiffness of the grease in the hub gear case.
(One more reason to lube the hub with the lower-viscosity white grease -- Lubriplate "130 AA" -- recommended by PYI.)

Loren

ps: Ken, I'll be glad when summer rolls around again, and perhaps we can meet up at a guest dock again.
 
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Maine Sail

Member III
My engine manufacturer(Westerbeke) says to not put into gear, the transmission manufacturer says you can put into reverse or neutral, the prop manufacturer(max-prop) says to leave in forward. ?????????

I just want to go sailing

Max-Prop says:

"4) PROPELLER USE The Max Prop works automatically. By putting the engine in gear the blades will engage in either forward or reverse. The best way to feather the propeller is;

  • Power at 2 to 3 knots in forward.
  • Kill the engine while still engaged in forward.
  • When the engine has stopped, if the shaft is still spinning engage the transmission in reverse to stop the freewheeling.
You can check to see if the propeller is feathered or not by taking the engine out of gear. If the propeller is not feathered the shaft will freewheel like with a fixed blade propeller.
In that case start the engine again and repeat the three steps. If your propeller has been greased properly it will feather in a fraction of a second as soon as you stop the shaft from freewheeling. Once the prop is feathered, you can either leave the transmission in gear or out of gear, it does not matter. DO NOT kill the engine while in reverse. In this case the blades will be in the reverse position and will not feather. You can actually use this feature to drive a shaft alternator."


I have always let them feather then put them in neutral or reverse when sailing with a Max-Prop equipped boat. If it does not feather, and you leave it in forward unfeathered, you can destroy your gear box in fairly short order.. In reverse they should not unfeather once feathered.. Our Westerbeke manual says reverse of neutral but not same direction of travel but it could depend upon which gear box you have connected to your Westy.. If the gear box maker says it is okay for N or R then either will be fine..
 

mherrcat

Contributing Partner
I tried letting the prop freewheel last weekend. I guess I picked up a little more speed, hard to tell; I probably should have tried locked and unlocked on the same tack and checked the meter...D'oh! Well, at least there was enough wind that I couldn't hear the shaft spinning. I'll try again next time, but I guess I figure locked is probably a little less wear on the shaft packing and cutless bearing. If I were racing I would go for the extra speed.
 

Starduff

Member II
Free wheel prop or lock it

My E28 manual also advises locking the transmission in reverse while sailing to reduce wear on the cutlass bearing. I don't think you get that much more speed free wheeling that will make the difference at the finish line. It's the mistakes or lack therof that counts most! :egrin::egrin::egrin:
 
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