Originally Posted by radmiral
I need to replace a bad set of props that came with my 1988 54 with 1292 's . They are 4 bladed and look like they have been redone. I only get 23kts WOT at 2300 . Does anyone have experience 3 versus 4 blades,and what size ?
I have a 1984 Bertram 54 ... 12V71TI engines (800 hp each) 3 blade 28x30's stock that are now 28x28's after years of abuse, reconditioning etc. My gears are 1.51 / 1.
I am not happy with the performance of the boat ... am pursuing new propellers once I finish with the overhaul of one of the engines (for the second time in a year .. long story).
The prop shop is going to pull both props to verify again that they are indeed 28x28 as they are now. Will also verify RPM's with a photo tachometer.
Prop shop concurs that 4 blade does not buy more performance ... also says 4 blade does not mean smoother but I have heard from many that 4 blade does mean smoother performance.
I'm hoping for WOT performance of 29 knots and cruise of 20-22 knots.
I am aware of a Bertram 54 with my same engines running 4 blade Michigan Wheel "Dyna-Quad" 28x30 props ... difference is that his gears are 1.75 to 1 and not 1.51 to 1 like mine.
His performance is 22 knots cruise ... 29 knots WOT. Where I want to be.
Either way ... slapping on a different set of props will not solve the issues of vibration or performance. Working out the issues carefully with some trusted professionals should.
PM is you want to continue communicating about the craft ... we have different engines but it's nice to have folks to talk to who have a similar craft.