Prop question

[Chillmark]

Good evening!

This is my first post, and it's about my prop. I've got a 25 year old 16-foot Mako with a Yamaha c115 xrt. My prop is all busticated and old. Theres no indication what its specs are. I went to the local Yamaha dealer and he gave me a 13 1/4 X 17 - k to replace it, based on a WOT of 5600, going full speed on a plane at light boat.

The new prop whined away at 56 or 57 and the boat barely got out of it's own way.

I didn't really feel like the guy I talked to at the store was particularly knowledgeable and this prop choice didn't help.

I don't know much about the numbers and what they mean, so I figured I'd come here and see what you all thought.

I appreciate any and all input you may have...thanks!

[Chillmark]

shameless bump anyone?

[SkinnyRaven]

Assuming the old prop worked why not take it in to a prop shop and determine the pitch? Yamaha wants your rpm's to be in the upper range of 5000-6000, the mechanics would like to see a minimum of 5800. I don't know the weight nor hull design of your boat, but I would never get 5600-5700 out of a 17pitch. I do however get 5800-6000 from a 4 blade 15 pitch.

[99yam40]

My prop is all busticated and old. Theres no indication what its specs are.

The new prop whined away at 56 or 57 and the boat barely got out of it's own way.

Old props still work, age does not make a difference.
Not sure what a made up word like busticated means

Pull the prop and look at the markings on the hub for the size.

Look at the Yamaha performance bulletins to see if you can find one like your set up and see what prop and speed they got. If yours will not get it close to that, then you have a sick motor

"barely got out of it's own way." does not mean much to anyone

[Chillmark]

thanks for the replies!

Busticated = busted, don't work

and something that won't get out of it's way is slow

didn't mean to be so unclear...

the prop is old but it goes, you are correct, However there's a big ol chunk out of it, and I'd like to use it as a spare. The prop is so old that I can't see any info on the the hub or anywhere else.

Raven I hadn't considered switching to a four blade. Worth considering I guess.