nordic95

Now that its winter I have some time to think about some of the things I thried on my boat and that didnt work so well. I have run many different combinations of props from 3 blade to 5 blade from labbed to stock. One set I tried was a set of 5 blades labbed and I experienced a vibration from start up to about 3500 rpms. After 3500 to WOT thay ran perfectly. So I took them to a local prop guy who checked them and said there wasnt anything wrong with them and that my hubs may be the issue. I have the bravo floe thru heavy duty hubs with the four black strip in them. The strips have fallen off and I reglued them on, could he be right about this? I wouldnt think so because those hubs work great with all my other props I have even though none of the others are 5 blades. Is it a 5 blade thing? Do I need different hubs?
Anthony

A.O. Razor

It is not a 5 blade thing. Rule of thumb is, that the more blades you run, the smoother it is. If that prop is the only one that has the vibration, I'll bet you anything it's a prop issue. I'd suggest you get a second opinion. Vibrations can be caused by several things, not only balance.

nordic95

Thats what I was thinking, but does it go away after 3500 rpms? And it is very slight, I feel it but passengers really dont at all.

A.O. Razor

The reason why it goes away at high rpms, is probably because the oscillation gets too fast to plant itself in the boat or because the "natural" point of oscilation is below 3500. Again, why is the vibration there. Is it because a pitch difference in one or more blades, another geometry difference ect. What it all boils down to is, that the balance, blade geomety, size and so on, needs to be identical. Also check the hub, barrel and thrust washer and see if it is straight.

bbladesprops

Ok,

5 blade props try to load up very hard.
If the water is aerated heavily Dependant on the hull, X dimension etc., the load and unload can cause whats seems to be a unbalance vibration.
Once the water is clean to the angle of attack, the vibration clears.

Call us and I can explain it in detail if you would like.

Brett