Looking for Advice

[billysboat]

It started with this post http://forums.iboats.com/showthread.php?t=406334 and now I've switched to this forum.
!966 Champion speed boat
17' length
351 ford w
volvo outdrive gears unknown
wot 5000 rpm's ( suggested wot 42-4400 )
current prop 14x22 LH stainless 3 blade
....without going through a lot of expense of trying different props it now seems I can use a prop change. It appears and what some friends are telling me I can increase the diameter of my prop. the clearance between the prop and the unit itself is about an inch or slightly more. What will happen if I increase the diameter only keeping the same pitch ? And by how much would a difference.
Or should I just change the pitch? From what I have noticed and having a 22 pitch already, would a 24 be a good choice?
I am looking forward to your suggestions or comments. Thanks

 

[steelespike]

Re: Looking for Advice

speraking generically:
You don't usually mess with diameter except in certain specific problems/applications.
Rule of thumb is ABOUT 200 rpm per inch. So a 2" pitch change would be about 300 to 400 rpm. If you can change your rotation easily you may find more choices in a rh
prop.Try to stick with one brand/model prop for more predictable results.
It appears you need a 3" pitch change.There are dealers that will let you exchange props to find the right one.A good prop shop could fine tune a prop adding or removing pitch or cup.