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Go Back   SailNet Community > On Board > Gear & Maintenance > Should transmission be in gear when sailing?
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Thread: Should transmission be in gear when sailing? Reply to Thread
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Topic Review (Newest First)
07-17-2005 03:55 PM
PaulBl
Should transmission be in gear when sailing?

It''s 100% the functiuon of the transmission and not anything to do with the engine or boat manufacturer.

I have a Hurth transmission and it goes in gear and in reverse while sailing. As far as I know all Hurth transmissions art like this and all sail drives don''t have to be. After that you are on your own.
07-11-2005 10:19 AM
jreddington
Should transmission be in gear when sailing?

I always put my engine in reverse when sailing for both the wear and drag reasons noted previously. The reason you use reverse as opposed to forward is that this takes up the gear lash (the small amount of "slop" before gear teeth engage) and the faces of the gear teeth engaged are the same ones as when you are going forward under power. Wouldn''t make much difference if you were in forward but to me this is the tie breaker by putting the gearbox under the stress conditions it sees normally.

Note. I also put the gear in reverse when docked or moored. The same propeller spinning can happen from current. I have never noticed shaft spinning while at my summer mooring probably because the current isn''t too bad. However, when I''m launced into the Connecticut River in the spring there is a steady 3 knot current. Put the transmission into neutral and I can hear the propeller spinning. I make sure that gearbox is in reverse before they launch. Would hate to see what days and days of 24 hr./day spinning would do to my gearbox.
05-30-2005 06:45 AM
928frenzy
Should transmission be in gear when sailing?

I conducted an experiment that convinced me that at least on my boat, a locked prop worked best. While under sail (engine off) I engaged and disengaged the tranny (in reverse). Regardless of sailing point, the boat speed (measured by GPS) increased by about 10% whenever the tranny was engaged.

My prop at that time was a fixed three blade well suited for the engine''s optimum operating RPMs. I have since replaced it with a folding two blade, so I don''t worry about prop drag anymore. ;^)
05-30-2005 05:59 AM
FalconEddie
Should transmission be in gear when sailing?

While the reasons for putting the transmission in gear are correct, in my humble opinion, but reinforced by a lifetime as a mechanic and the past 20 years as a marine mechanic, there is another good reason that I read some 20 or so years ago in Practical Sailor, which I tested myself.

The report had to do with conflicting theories of drag from the propellor, and this is what they found:

A free-spinning prop quickly enters it''s intended range of efficiency where it gets a full mechanical grip on the water. If the props RPM''s 200 or 300 or even 400, imagine how hard you would be working to do that by hand. That''s horsepower and it translates into considerable drag. They had numbers. I forget them.

A locked prop produces some drag at slower speeds that is a tiny bit higher than a slowly spinning prop, but once you start making more than 3 knots, the spinning prop makes more drag. At speeds approaching five knots, locked props begin to cavitate, significantly reducing drag. Yes, there''s still drag - you don''t get cavitation without pumping horsepower into it, but it''s far less than a fully spinning prop that has a secure grip on the water your trying to slip through.

Just my 2 cents.

Fair winds and fine seas, all.
05-29-2005 11:26 PM
sdsailor99
Should transmission be in gear when sailing?

Folks,
The reason to put the saildrive - or any prop for that matter, in gear is to reduce drag. It is more significant with a folding prop, but a spinning prop creates considerable drag compared to a rottating one. There may be some issues on bearing wear on long sails, but this is secondary.
Non-geared (Martec type)folding props must be set so they are generally horizontal before locking them in gear so the water pressure closes the blades. Do this by putting the transmission in gear with the engine stopped and then turning the shaft to a preset mark.
Many saildrives have geared folding props that force the two blades to the same opening position so they close under sail regardless of the rotation. However they will continue to rotate unless put in gear.
Even fixed blade props have less drag when stopped.
Just think of a helicoper autorotating (freewheeeling with no engine) vs one with the rotors stopped. I assure you the latter will fall much faster (less drag.)
I think people put transmissions in reverse because the thottle lever is less in the way.
05-25-2005 01:54 PM
hamiam
Should transmission be in gear when sailing?

ive had 2 boats with yanmars; both manuals suggested putting it in reverse. not sure the reason for this. certainly stops the shaft from turning so may be good for both the engine and for boat speed.
05-24-2005 06:12 PM
KenD
Should transmission be in gear when sailing?

I''am not Totally sure but I went to a Yammar class and they suggest putting the trans in reverse because, the rear output bearing is not lubed unless the motor is running and the trans in gear, putting the trans in reverse while really sailing keeps the shaft from turning and therefore prevents the bearing from rotating unlubed.Thus saving you Big bucks by not having to overhaul the transmission.
05-22-2005 06:43 PM
dman
Should transmission be in gear when sailing?

Good advice Paulo.If you do not know that, you better do some reading up on your particular transmission because it can lead to serious damage ,besides that, there are probably other things you will learn in the process that you are neglecting or have overlooked.The worst thing you can do is take anything you heard from someone down at the dock as fact(learn all you can about your equipment).These posts should get you thinking,then do your investigating.
05-22-2005 02:03 PM
PCP
Should transmission be in gear when sailing?

If you have a Volvo Saildrive, put the gear in reverse.
05-22-2005 06:02 AM
kimberlt
Should transmission be in gear when sailing?

what engine-prop do you have?
fair winds,
eric
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