How do I measure a prop?

[Muppet]

1974 150 hp merc, I have a 17 pitch on there now, but would like to know what size it is that I should be looking for when buying online. It has 15 spines.

 

[ErikDC]

Re: How do I measure a prop?

Just grab a tape measure and extend the tape from the center of the hub to the outermost tip of a blade and multiply by 2. I'd suggest that you find out where your nearest marina or marine supply store is and take the prop with you, they should easily be able to tell you anything you want to know and give you some ideas about what blade type and/or pitch would optimize your performance.<br /><br />Edit: Nearly forgot, they will probably ask the size and what type of boat you have and what RPMs you're running at WOT, what your hole shot is like, etc. I've been out of the prop biz for about 10 years now so I'm running with basic info, I've forgotten most of the good stuff, my apologies. Hopefully someone else here has better info than I.

 

[AJ168]

Re: How do I measure a prop?

There's the diameter and the pitch. The pitch is the theoretical distance that the prop would trave through the water in one revolution. But of course it doesn't travel that full distance due to other factors. The size propeller needs to be matched with the type of engine you run, the type of hull, and what the boat will be used for. Erik's right, your best bet is to go to a marina or a propeller shop and talk to them.