Re: Any PSC37s with 4-blade Variprops out there?
We thought it was time to give an update. Mythago was outfitted with a Variprop DF-107 4 blade 18” X 12”(forward) X 9” (reverse) this last spring. Installation did end up requiring the rudder to be dropped to the point that there was bare rudder post behind the prop shaft and at that point the VariProp just squeaked on. On sea trial, we were able to get up to 3100 rpm maximum and we were seeing hull speed at around 2600 rpm which according to Dave Gerrs propeller book calculations is about right. If necessary, you can adjust both forward and reverse pitch in the water but I'm glad it didn't come to that. A couple of the significant differences over the old 3-blade ProWell prop... this one is much better balanced and smoother running, and, going from one gear to the other the new prop doesn't make a "thump" when the hub hits the stops. We did try a crash stop from 7 knots and there wasn't any problem. With the 4 blades, we slowed very quickly without a lot of commotion which was a great improvement over this props predecessor. The Variprop has a "Soft Stop Multi-Disc brake" built into the hub to minimize the impact on the stops and I'd say it does make a difference and maybe that will pay off in greater longevity?. As for Prop walk, it's still there but is signficantly lessened in routine use. Having the 4 blades allows the same power transmission into the water at a lower rpm which to me makes sense in that less lateral movement is created. Add on the power in reverse and the walking tendency increases noticeably. All in all, we are happy with the purchase. It doesn't seem to have made any real difference in fuel economy but we are confident that we can get all of the power of the engine into the water now when it proves necessary. Thanks to everyone for their thoughts and observations.... this is an awesome group!
S/V Mythago 1995 PS37 #301 ON831667