Locking engine in reverse?

[birnbaumr]

Hi, I've got a 2005 Hunter 33, with a 29hp Yanmar engine. Several people have told me its a good idea to lock the engine in reverse when under sail (rather than leaving it in neutral). Some reasons include less wear on the transmission and less chance of a propeller snaring a lobster pot.

Does anyone have an expert opinion on this? Thanks.

 

[Lee Coller]

What's right for your engine may not be right for someone else's. Check with your local Yanmar distributor. For my engine (4JH3E, 56hp on my 04 44DS), they say not to lock it in reverse under sail, the transmission can actually be damaged if do.

 

[jdhohmann]

Very large forum!!!

Guys and girls, there was a very large forum with this being the main concern, I am sure if you search it here, you will find it quite easily

here is the link

http://forums.hunter.sailboatowners.com/showthread.php?t=107118&highlight=transmission

 

[Sailgunner]

What's right for your engine may not be right for someone else's. Check with your local Yanmar distributor. For my engine (4JH3E, 56hp on my 04 44DS), they say not to lock it in reverse under sail, the transmission can actually be damaged if do.

Who are "they."

 

[timvg]

And I've been told by Yanmar that either is OK. I have a 4jh2e on my 40.5.

 

[Benny]

The only expert opinion is that of the manufacurer. For Yanmar trannys the manufacturer indicates it is OK to let it freewheeel or place it in reverse. Wear and tear considerartions are nill or not significant with either choice. A Yanmar tranny properly lubricated will last thousands of hours. There are claims that a locked prop induces more drag than a freewheeling one but the so far they are unsubstantiated. If you do place the the tranny on reverse don't forget to slow the boat down to below 1 knot before removing from gear as not to abuse the the gear selectors and clutches. Some say they start the engine in reverse to avoid having to slow down; It just provides added pull on the shaft. What do I do? It is my preference to let it freewheel.

 

[Maine Sail]

Benny is right

The only expert opinion is that of the manufacurer. For Yanmar trannys the manufacturer indicates it is OK to let it freewheeel or place it in reverse.

Benny is right, somewhat. Yanmar suggests neutral with the Kanzaki gear boxes but not forward or reverse. Universal & Westerbeke recommend reverse or neutral for their JS or Hurth/ZF gear boxes. Yanmar DID NOT always recommend neutral and for a while said reverse or neutral but they have changed their recommendation to neutral only.

There are claims that a locked prop induces more drag than a freewheeling one but the so far they are unsubstantiated.

Unsubstantiated? Actually there are two white papers, one by MIT, and one by the University of Strathclyde Ocean Engineering Dept (White Paper Link) plus a UK magazine where they actually towed real sailboats through the water measuring drag with strain gauges. MIT the University of Strathclyde and Yachting Monthly (Article Link) and then my own experiment (Video Link) all agree and show that a standard Michigan style wheel causes more drag locked than it does freewheeling.

As for reverse or neutral if you have a Yanmar it should be neutral. I lock mine unless I want to sail faster then I shift to neutral. Keeping it in forward can damage many gear boxes..

 

[Benny]

Maine Sail I knew you were testing the drag for locked or freewheeling props but I had not seen the results. It confirms my intuition but what was really surprising is the amount of drag present. A difference of 20 to 25 lbs of drag at about 5 knots is significant. I understand the test was performed for a Michigan style prop and that results will vary with other props but I would think that the relationship of around 2:1 would be maintained. Keep up the good work, thanks.