Nomad Willy
Guru
This is the propeller I've been wanting for quite awhile now. It's a Michigan MP that's made in this country and is listed as a commercial workboat prop. I remember it was almost universal in the 50s and 60s on fishing boats and other commercial vessels. Most fish boats look more like trawlers that the fish boats of the 40s and 50s and so do their props. Most of the fish boats in Thorne Bay have big wide flat transoms and flat bottoms just like contemporary trawlers and if you've got any ideas about why it may make interesting conversation.
I did some running about a couple hours ago and the new MP prop is smoother and has more reverse thrust but only slightly. It seems to perform at about 2250rpm exactly the way the other prop performed at 2300rpm. That fits very well with the fact that WOT rpm is down 100rpm from 3000. So I'm now 100rpm over propped. It's very noticeable in the harbor as I need to spend more time out of gear. This symmetrical (blade) propeller with (apparently) no rake is known to be a bit less efficient than the more usual skewed props found on most boats. Doing speed/rpm comparison runs in both directions it seems to perform at 2250rpm about exactly as the other prop did at 2300. But that should be expected by loosing 100rpm at WOT. So my conclusion at this first act point is that it's not much different that the other prop other than everything happens 50 to 100rpm slower and it is noticeably smoother. I think if I reduced the pitch 1" I'd be at 3100 at WOT so I'm inclined to have (at a good prop shop) cut away a tad bit of blade area to pick up 100 to 125rpm. I consider being under propped 25 to 50rpm to be ideal.
I put the boat on the grid at the last moment so did'nt have time to go to town and get new zincs but the boat should be hauled in 4 to 5 months. I'm satisfied that I did get the prop changed and I borrowed a pressure washer from a friend so now we have a clean bottom and a bit smoother prop for the trip south.
I did some running about a couple hours ago and the new MP prop is smoother and has more reverse thrust but only slightly. It seems to perform at about 2250rpm exactly the way the other prop performed at 2300rpm. That fits very well with the fact that WOT rpm is down 100rpm from 3000. So I'm now 100rpm over propped. It's very noticeable in the harbor as I need to spend more time out of gear. This symmetrical (blade) propeller with (apparently) no rake is known to be a bit less efficient than the more usual skewed props found on most boats. Doing speed/rpm comparison runs in both directions it seems to perform at 2250rpm about exactly as the other prop did at 2300. But that should be expected by loosing 100rpm at WOT. So my conclusion at this first act point is that it's not much different that the other prop other than everything happens 50 to 100rpm slower and it is noticeably smoother. I think if I reduced the pitch 1" I'd be at 3100 at WOT so I'm inclined to have (at a good prop shop) cut away a tad bit of blade area to pick up 100 to 125rpm. I consider being under propped 25 to 50rpm to be ideal.
I put the boat on the grid at the last moment so did'nt have time to go to town and get new zincs but the boat should be hauled in 4 to 5 months. I'm satisfied that I did get the prop changed and I borrowed a pressure washer from a friend so now we have a clean bottom and a bit smoother prop for the trip south.
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