propellers - large or small?

[anderbra]

I need to replace my prop. The Volvo dealer suggests I use a Volvo 15X9, as recomended for my MD7A, 13 hp engine. A local competitor is proposing a 13X8 Slipstream for the same situation.

I realize the technology in these props are quite different. All other things being the same, which of the above propellers would give better cruising speed?

Any oppinions? Thank you in advance.

[Hawkeye25]

There are sound arguments in favor of both, but personally, I would go with the larger, conventional prop. It works better when docking, though you give up a smidge when sailing, but only when the wind is JUST BARELY enough to make hull speed. Any more wind than that and the additional drag is overpowered by additional drive out of the sails.

Now you'll get others who'll claim the wind in your area is ALWAYS JUST BARELY enough and the bow of your boat can take those creaky, crunchy introductions to the dock forever. They call themselves 'purists'. I do fiberglass repair and I call them 'customers'.

I just wish I could put a big grin here.

[Karletto]

Originally Posted by Hawkeye25

but personally, I would go with the larger

+1..................

[dhornsey]

Everything I've read on the subject indicates than in general, a prop with a larger diameter is more efficient.