Terry, my 11.8x10 Solas 4 blade has a 7/8 inch clearance from Cavitation plate. Previous owner raised the engine 1-1/4 inches off the transom and when motor is all the way down and you eye ball the cavitation plate the clearance to bottom of hull is only 1/4-3/8 inches and should be min. 1 inch. I could lower the motor back were it is suppose to be or tilt the motor back slightly.
I have no idea why they raised the engine but I feel the boat was always empty when they had it and got on plane faster and higher speeds.
Reverse, it cavitates very easy. I will wait until I install a new motor .
The winning noise came from the hub to shaft and bearings and after 3 blade changes it stopped winning but barely could fit the propeller nut and cotter pin it as hub was 1/8 inches from engine.
The 11.8x10 solas 4 blade has to much pitch to get to low end of the rpm limit. Ok for me as I like low end thrust for cruising 6 knots and lower rpm for sound noise.
Dave
Terry wrote:opie wrote:Dave is right about a 4 blade propeller (especially Solas) giving out strange sounds at about 2k rpm. (See this
(LINK)
I experimented and ground off the cupped edges of the 4 blade and the noise almost disappeared. I will stick with 3 blade props, thank you. So I think you can be relieved to know it is not a Honda mechanical problem.
The function of the cupping on the trailing edges of the propeller is to provide more grip so that the prop gets a better bite on the water and have less slippage which translates into more forward thrust. Grinding the cupped edges merely defeats the purpose. I have a Solas Alcup 4 X 11.4 X 10.5, I had the pitch altered by a prop shop so it is not factory standard but it works well. I might wonder if perhaps the larger diameters are a contributing factor. With my 11.4 diameter I have more clearance between the prop edge and the anti-cavitation plate and so no noise. Perhaps with the larger diameters the singing noise is a result of the prop edge breaking the surface of the water just under the plate. I have looked back at the engine while at WOT and noticed that the anti-cavitation plate is just skimming over the water surface like a ski so there is not much room for clearance. Those 12 inch diameters are almost touching the plate so if there is any air rushing under the plate the tip of prop may be sucking some of it. Just another theory though, I could be wrong. Personally I don't think the Honda swings a large enough prop, I think they should have a larger clearance under the anti-cavitatuion plate to accommodate a 12 inch prop with at least a half inch clearance to spare.
with a new Honda 4 blade 11.8x9. The propeller swap was a snap (out of water), and the motor passed it's "Garbage Can" run prior to my wife and I launching her yesterday. I how have what sounds like a (loud) bearing noise at RPMs between 1500 and 2200 RPM (while in the water). No problems at lower or higher RPMS. There is no similar noise in reverse, nor when run out of water (with a hose supplied "ear muff" flushing adapter). Thrust Bushing problem? Thoughts? Are there any particular tricks to propeller replacement on Honda BF-50's that I missed? I've pulled and re-installed the prop (in water) with no change. All parts appear to be installed correctly.
