My wife just loves the 72' 28 ft flybridge Sports Express. I have my eyes on one but before I decide, I have questions about the power set-up. The very kind, Rachel, at the Maritime Museum, stated that originally, the vessel had 245 hp with a 1.5:1 through a 3:1 gearbox and 1410 props in some instances. So, with the 330s and 1:1s, what's my ideal prop size?
Hopefully, someone reading this has had experience with the set-up and will pass along greatly appreciated knowledge. I'm trying to avoid the cost of experimentation. The story goes that the last props on the vessel were 1312s and I have no info as to their performance.
I just ran a few numbers through the Michigan Wheel online calculator. I assumed a few things for the calculations: 35 kts top speed, target RPM at WOT as 4400. Based on that and a 1:1 gearbox the recommended props come out as a 13x12 3 blade or a 12x13 4 blade.
So unless you have a good indication that the top speed with that power should be significantly off from 35 kts then the 13x12 props are most likely at least pretty close to ideal.
Thanks Oldest!
It sounds like they should have left the props on? They were 13 12. The owner was told to try 13 9 cupped. I'm not sure what that would do except lower top end.
I think it's going to burn lots of fuel.
In your opinion, is this going to be an expensive boat to cruise with?
We go from Aurora NC to Ocracoke NC. That's about 80 miles round trip.
The current props are 13x12 with 1:1 gears, and the boat reaches 24 knots at 4500 rpm WOT. The Crusader manual says WOT should be 5000 rpm.