I motored up to Oceanside this weekend. I've noticed that my motoring speed seems to be a bit slow. We had some headwinds, but I was only getting about 4.2 knots @ 2000 rpm with a 3 bladed prop. M25 engine. I can get about 4.6 knots SOG at 2400 rpm but fuel consumption goes up. Just curious what kind of motoring speeds some of you folks are getting?? Thanks... Jim H
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Motoring SOG
M25xp w/3 blade Cambell Sailor Speed over ground is on average................ 1800 RPM - 5 kt 2200 RPM - 5.5 kt 2450 Max RPM - note that 3200 is max RPM stated in the manual for this engine but I've never seen it, I figure I'm missing about 400 RPM....something else to fuss with when I'm not sailing. Last winter I went thru the fuel system up to the high pressure pump maybe this winter I'll do the exhaust side.....Engine runs fine never had a problem and I reach hull speed so I try not to stress about it....
M25xp w/3 blade Cambell Sailor Speed over ground is on average................ 1800 RPM - 5 kt 2200 RPM - 5.5 kt 2450 Max RPM - note that 3200 is max RPM stated in the manual for this engine but I've never seen it, I figure I'm missing about 400 RPM....something else to fuss with when I'm not sailing. Last winter I went thru the fuel system up to the high pressure pump maybe this winter I'll do the exhaust side.....Engine runs fine never had a problem and I reach hull speed so I try not to stress about it....
slight breeze
Hmmm.... I took her out briefly this morning in Oceanside Harbor (stayed within the breakwater) and got about 4.4kts @ 2000 rpm and about 5.4 @ 2400 rpm. The people that clean my bottom also clean the prop and it was just done a few days ago. Someone mentioned the packing gland. I repacked it myself a few months back. I have the drip rate about right and it doesn't get hotter than luke-warm after heavy motoring....so I guess that's not the issue. I'll probably haul the boat next year and I'll have the prop pitch checked etc. I guess I'm close to what should be expected. Maybe I'm getting impatient as I get older?
JimmyD
Hmmm.... I took her out briefly this morning in Oceanside Harbor (stayed within the breakwater) and got about 4.4kts @ 2000 rpm and about 5.4 @ 2400 rpm. The people that clean my bottom also clean the prop and it was just done a few days ago. Someone mentioned the packing gland. I repacked it myself a few months back. I have the drip rate about right and it doesn't get hotter than luke-warm after heavy motoring....so I guess that's not the issue. I'll probably haul the boat next year and I'll have the prop pitch checked etc. I guess I'm close to what should be expected. Maybe I'm getting impatient as I get older?
JimmyDComposite Prop
Two years ago I bought a composite prop from CDI. The "Extendo" has an extended hub that allows a C30 to carry a 15X10 prop which is the right size for a M25. I easily do hull speed, yes, I said hull speed, at less than 2500 rpm, and I cruise at 6kts around 2000-2200 rpm. Try it, or email me about it. IT WORKS!!
Two years ago I bought a composite prop from CDI. The "Extendo" has an extended hub that allows a C30 to carry a 15X10 prop which is the right size for a M25. I easily do hull speed, yes, I said hull speed, at less than 2500 rpm, and I cruise at 6kts around 2000-2200 rpm. Try it, or email me about it. IT WORKS!!
The problem is...
Look, the real issue is that the C30 has never been changed below the water line. Originally, the boat came standard with an atomic 4 gas unit, turning 3600 rpm with a direct drive 1:1 transmission. A 12 X10 three-bladed prop could very well do hull speed with that kind of speed; however, with the advent of newer, smaller, more efficient diesels, the rpms at the prop have dropped by as much as half because of heavy duty 2:1 ratio transmissions. Even at full power, 3200 rpm, you are still only getting 1600 rpms to the prop.
Look, the real issue is that the C30 has never been changed below the water line. Originally, the boat came standard with an atomic 4 gas unit, turning 3600 rpm with a direct drive 1:1 transmission. A 12 X10 three-bladed prop could very well do hull speed with that kind of speed; however, with the advent of newer, smaller, more efficient diesels, the rpms at the prop have dropped by as much as half because of heavy duty 2:1 ratio transmissions. Even at full power, 3200 rpm, you are still only getting 1600 rpms to the prop.
One more bit of great news
I almost forgot... I think I did say that the extendo was a two bladed prop. What I need to tell you is that I also increased my sailing speed by at least a half a knot in the lightest breeze, and you can forget about prop walk. I just put it in reverse and go where I WANT to go. I tellin' ya man, it's a good thing. One more thing, As I said I put the prop on two years ago. Well, I started my masters and did not have time to do a bottom job until this last spring. I read where some folks were using Desitin ointment as an antifouling treatment. I tried it. When I hauled-out, after two years of not doing anything to the boat the prop and most of the shaft were almost clean. It only took me minutes, literally, to wipe off the prop and shaft...
I almost forgot... I think I did say that the extendo was a two bladed prop. What I need to tell you is that I also increased my sailing speed by at least a half a knot in the lightest breeze, and you can forget about prop walk. I just put it in reverse and go where I WANT to go. I tellin' ya man, it's a good thing. One more thing, As I said I put the prop on two years ago. Well, I started my masters and did not have time to do a bottom job until this last spring. I read where some folks were using Desitin ointment as an antifouling treatment. I tried it. When I hauled-out, after two years of not doing anything to the boat the prop and most of the shaft were almost clean. It only took me minutes, literally, to wipe off the prop and shaft...
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