Kastel Brothers had the prop ready in half the time promised and it was on the boat the next morning in time to head out for Kent Narrows on a beautiful day. I would have liked to sail but needed to give the powerplant a good sea trial. The engine ran smoother than it has since chopping up that branch in the Dismal Swamp last fall and everything seems rock solid with no sign that shaft, mounts, or strut were damaged by the heavy vibration.
The boat picked up .2 knots of speed at my usual cruising RPM of 2300. I was a bit disappointed but not surprised therefore to find next that I had lost about 150 RPM at the top end. It just goes to show how hard it can be to get everything right, even for someone who has done a lot of prop calculations and knows all the issues.
Kastel’s had called the first day to tell me that the remaining blade of my old prop actually measured 13 inches of pitch instead of the 14 stamped on it. I told them it was perfect for the boat and to match it as closely as possible. I was glad we’d sent them the old one to check.
Later, they called to tell me that my old prop was a short hub version (pretty hard to obtain now). That explains the amount of hub taper I had showing ahead of the hub. They wanted to be sure I had sufficient clearance to the strut. I assured them that I did because I actually have excessive distance between strut and hub due to the PO adding a Drivesaver without shortening the shaft. This call made me over confident that they were covering all the bases.
I called them from the boat after anchoring south of Kent Narrows. They hadn’t been sure that the inch difference in pitch wasn’t from the prop strikes so they pitched to the full 14 inches. I then asked what I should have before: did the new prop have a wider blade profile? They said that, yes, they had noticed that it did.
Damn, this is why I always make a pest of myself and go in and check everything personally when I can. Blade area has to be traded for pitch. I probably would have left the wider profile prop at the 12 inch pitch and certainly would have told them not to go over 13. However, I didn’t have a car and it seemed like they were on top of everything.
So, I’m now slightly over pitched. It’s not too serious. I’m just 50 RPM shy of 2500 WOT so, if the boat were clean and light, would probably get to the 100 RPM extreme limit of permissible tolerance. I wouldn’t want this prop on a boat operated by someone who might run around at WOT for hours but I can run a couple hundred RPM slower and the engine seems happy. There isn’t a hint of smoke in my new cruising range of 2100-2200 and the engine is quieter. I start to see a bit of light gray smoke at 2300 and, when it tops out at 2450, it’s smoking more than I’ve seen but is still the proper light grey. No oil in the crankcase breather liquid trap either.
I can live with this wheel for the time being. I’ll need to paint the bottom before long and will probably have an inch of pitch bumped out of it when I haul. It’s close to the way we used to prop commercial boats so I may decide that it’s OK by the time I’ve gotten it back to Maine.
After a pleasant night anchored south of Kent Narrows, I went through the bridge and into Mears Marina early to beat the rain and wait out thunderstorms. Neither ever arrived although there were light showers while I did three loads of laundry.
Last night, I went over to Harris’s Crab House to finally have a mess of steamed crabs. I’d planned to leave this morning but it’s cold and blowing hard across the slip and I’m feeling lazy so I decided to spring for another night and just stay right here. It will be calm and a bit wet tomorrow so I think I’ll run up to the head of the Sassafras River or maybe Chesapeake City. I need to be in Atlantic City by May 8 to meet crew for the leg to NYC and we seem to be entering a turbulent weather pattern so I want get some lay days into the bank.
The boat picked up .2 knots of speed at my usual cruising RPM of 2300. I was a bit disappointed but not surprised therefore to find next that I had lost about 150 RPM at the top end. It just goes to show how hard it can be to get everything right, even for someone who has done a lot of prop calculations and knows all the issues.
Kastel’s had called the first day to tell me that the remaining blade of my old prop actually measured 13 inches of pitch instead of the 14 stamped on it. I told them it was perfect for the boat and to match it as closely as possible. I was glad we’d sent them the old one to check.
Later, they called to tell me that my old prop was a short hub version (pretty hard to obtain now). That explains the amount of hub taper I had showing ahead of the hub. They wanted to be sure I had sufficient clearance to the strut. I assured them that I did because I actually have excessive distance between strut and hub due to the PO adding a Drivesaver without shortening the shaft. This call made me over confident that they were covering all the bases.
I called them from the boat after anchoring south of Kent Narrows. They hadn’t been sure that the inch difference in pitch wasn’t from the prop strikes so they pitched to the full 14 inches. I then asked what I should have before: did the new prop have a wider blade profile? They said that, yes, they had noticed that it did.
Damn, this is why I always make a pest of myself and go in and check everything personally when I can. Blade area has to be traded for pitch. I probably would have left the wider profile prop at the 12 inch pitch and certainly would have told them not to go over 13. However, I didn’t have a car and it seemed like they were on top of everything.
So, I’m now slightly over pitched. It’s not too serious. I’m just 50 RPM shy of 2500 WOT so, if the boat were clean and light, would probably get to the 100 RPM extreme limit of permissible tolerance. I wouldn’t want this prop on a boat operated by someone who might run around at WOT for hours but I can run a couple hundred RPM slower and the engine seems happy. There isn’t a hint of smoke in my new cruising range of 2100-2200 and the engine is quieter. I start to see a bit of light gray smoke at 2300 and, when it tops out at 2450, it’s smoking more than I’ve seen but is still the proper light grey. No oil in the crankcase breather liquid trap either.
I can live with this wheel for the time being. I’ll need to paint the bottom before long and will probably have an inch of pitch bumped out of it when I haul. It’s close to the way we used to prop commercial boats so I may decide that it’s OK by the time I’ve gotten it back to Maine.
After a pleasant night anchored south of Kent Narrows, I went through the bridge and into Mears Marina early to beat the rain and wait out thunderstorms. Neither ever arrived although there were light showers while I did three loads of laundry.
Last night, I went over to Harris’s Crab House to finally have a mess of steamed crabs. I’d planned to leave this morning but it’s cold and blowing hard across the slip and I’m feeling lazy so I decided to spring for another night and just stay right here. It will be calm and a bit wet tomorrow so I think I’ll run up to the head of the Sassafras River or maybe Chesapeake City. I need to be in Atlantic City by May 8 to meet crew for the leg to NYC and we seem to be entering a turbulent weather pattern so I want get some lay days into the bank.
