prop rotation at anchor in current

Post by **craw_daddy** » Wed May 30, 2007 7:04 pm

General question: Can the transmission be damaged if the prop is allowed to rotate while anchored in a current? The boat is a 2006 28te with a 315hp yanmar -not sure about the tranny model.

Post by **DougSea** » Thu May 31, 2007 9:05 am

I've never heard of this as an issue. You'd have to be in a REALLY substantial current before the prop/shaft would rotate fast enough to do any kind of damage.

I recall reading once that on a high speed twin screw boat that you should not let the shaft of a shutdown motor freewheel at high speeds when using only one motor (engine breakdown, heading home on the other). This supposedly could cause a problem with the shaft seal on the shutdown motor as it would not be getting any cooling water pumped to it as it rotated.

If this was a real issue for most boats I'd think you'd be reading about all kinds of shaft brakes and such.

Post by **Mariner** » Thu May 31, 2007 11:42 am

This is an issue on sailboats, and people do often employ the use of shaft brakes. I would recommend, if possible, that you put the transmission in reverse which will ensure that it will not turn. The added benefit of this will be that it will help keep your boat pointed into the current.

Post by **craw_daddy** » Thu May 31, 2007 5:47 pm

that is where I read about it on a diesel forum re:sailboat IB tranny damage due to prop rotating. I just wanted to make sure this wasn't an issue with this larger deisel.. putting it in reverse while at anchor seems like it should stop that..

Thanks. --Dave

Post by **Mariner** » Fri Jun 01, 2007 12:39 pm

I should point out that the risk of damage is only to be of concern if the current is rather strong. The reason it's an issue on sailboats is because they're often sailing along at 6-7 knots, which is the same or even faster than when under power, meaning the prop is turning the shaft at or even sometimes above it's wide open speed. That's not good for it. However, in light current, an anchored powerboat's propeller may only turn one knot or less, which it can probably do without fear of overheating. Still, it's probably best to pop it into gear to keep it from spinning.

Albin Owners Group

Albin Owners Group

prop rotation at anchor in current

prop rotation at anchor in current

prop shaft rotation