Bravo 3x prop' size?

[PCUK]

Would any prop' experts like to give me an estimate of the prop' set to start with. I can calculate standard shaft drive props' but have no experience of duo propeller sets.
24ft wll
28ft oal
Displacement 2.5 tonnes
250 hp at 4,200 rpm
Reduction ratio 2.2
A starting point would be much appreciated.

 

[QBhoy]

Diesel is she ? Problem is…with that particular bravo 3 and its props…it’s an expensive guessing game. Hopefully you can get some to try out perhaps. I wouldn’t be so bold as to suggest to another what’s required, but if it was my problem, I’d start with a set of 22”‘. Just quickly throwing your known numbers and then some assumptions of around 30ish mph, 15% slip etc etc. it’s likely between a set of 20’s or 22’s. But to complicate things further…these are only assumptions and add in the diesel (if she is)…they sometimes need to be pitched rather fiercely, to load her up low down, to build some boost. Tough one. That’s where I’d be at anyway.

 

[jointventureII]

Would any prop' experts like to give me an estimate of the prop' set to start with. I can calculate standard shaft drive props' but have no experience of duo propeller sets.
24ft wll
28ft oal
Displacement 2.5 tonnes
250 hp at 4,200 rpm
Reduction ratio 2.2
A starting point would be much appreciated.

When you work this out, let me know as I'm trying to get hold of a Bravo 3x (or XR)!

I found some of those US forums such as offshoreonly have some really knowledgeable contributers, try there if no joy here

 

[PCUK]

Thanks friends. Yes diesel! I've got a set of prop's for a first attempt but they are three blade so I'm sure they won't be anywhere near correct. Mind you, I bought them off Ebay listed as aluminium for £90 the set with one lightly damaged. When they arrived turned out that they are stainless. So a bit of a result even if they are wrong!