Practical Boat Owner reader David Blackborow is trying to find out the best way to close the gap between the rudder and propeller on his boat

How do you close the gap between the rudder and propeller?

My boat is kept on a drying mooring and, as you can see from the above photo, there is quite a gap between the rudder and propeller.

Unfortunately, due to my mooring being in a busy place, ropes and warps that are not maintained by other users tend to float free and can easily snag and become entangled in my prop, which is quite a problem.

I have a rope cutter which isn’t very good but I’d sooner close the gap between rudder and prop, or cage it in some way to prevent boat ropes getting caught so readily.

Any ideas?

David Blackborow

Tony Davies replies: At first glance this seems like quite an unusual problem, but thinking about it, maybe it’s not so rare.

The obvious solution as you mention is to fit a prop cage, but this needs to be strong enough to resist underwater impacts that could distort it so it ends up fouling the propeller.

My next thought was to fit a skeg beneath the keel to try and dissuade ropes from rising up in the gap.

However, unless the gap was totally closed there’d always be a way for ropes to inevitably find their way through.

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A more drastic solution would be to have the rudder modified with a spigot on the lower edge that fitted into a socket on the skeg.

In this case, the skeg would need to be solid enough not to distort and then jam the rudder if the boat were to sit on a hard object – but it would be an expensive project and may still not entirely solve the problem you face.

You could consider fitting a better quality rope-cutter, but even they can get overwhelmed at times.

I tend to think that whatever you do it could end up creating more of a problem than that which you are suffering now.

However, it’s quite possible that other readers may have already come up with better ideas to solve this problem if they’ve faced it themselves, in which case we’d be delighted to hear from them. Please email at

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