prop advise

highestr8 · Post by **highestr8** » Tue Aug 28, 2012 8:16 pm

In need of a 13" x 16" x 1" RH 3-blade prop. I have located a michigan dyna jet 13" x 14" x 1, cupped.

How significant is that 2" pitch difference? Can a cupped prop be cupped again to increase the pitch more?

Thanks, B

mfine · Post by **mfine** » Tue Aug 28, 2012 8:51 pm

In my experience, 2" of pitch can be the difference between a boat with decent performance and one that struggles to get on plane. In your case you would be going the other direction where you could be losing more than 10% of your top speed and you may also introduce the possibility of over reving the engine but acceleration would be improved.

You should not buy a prop based on what is available cheap. The prop you need, whatever size that may be, is readily available from multiple manufacturers and venders. Many will allow you to exchange the prop so you can water test and find the right size and pitch for your boat and engine combo. That is a service worth paying for if you have strayed from stock and don't have a good reference point to begin from.

highestr8 · Post by **highestr8** » Wed Aug 29, 2012 7:47 am

Thanks for the input. I know you are right to buy the correct prop. Maybe you can provide a little more help.

This is for a chris craft 20' grand prix, 427 eng.

Lost the current prop, no idea if it was orig. The boat ran and handled great although it porpoised at upper speeds.

My hull card calls for prop #3476. I've found only one reference on the Web which says this would be 14 x 15.

Another club member was helpful and checked his prop (which he believes is original since the boat has only 150 hours). His prop is a 13 x 16. And his boat runs flat at high speed.

Any thoughts? Thanks.

drrot · Post by **drrot** » Wed Aug 29, 2012 8:36 am

The 1968 specs call for a 14X15. I'd find the larger diameter, it will grab more water and perform better.
A 13X14 will allow you to over rev the engine pretty easy

tph · Post by **tph** » Wed Aug 29, 2012 9:19 am

Your 13x14 can be repitched to 13x16 by any good
prop shop.
tom

Don Ayers · Post by **Don Ayers** » Wed Aug 29, 2012 9:44 am

If you went with a new four blade you would be amazed. Call the folks at OJ. They have an exchange program so you can dial it in.

highestr8 · Post by **highestr8** » Wed Aug 29, 2012 2:57 pm

Thanks for the advise and for confirming the original size prop. I have ordered one and should be buzzing the lake on Saturday.

Lee Dashiell · Post by **Lee Dashiell** » Tue Aug 04, 2015 7:58 am

Don Ayers wrote:If you went with a new four blade you would be amazed. Call the folks at OJ. They have an exchange program so you can dial it in.

I was curious about these new 4 blade props and how they ran. I have recently purchased a 1958 CC 17' Sportsman with a KFL 131 HP motor and I was thinking that I would like to give one a try. Did you keep the same pitch and diameter when you switched to the 4 blade?

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