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I have a Westerbeke 63C. The fixed prop that was replaced was a 20×13 …. which was too much prop…
Rick
Temerity #73On 9/19/08, () < ([email][/email])> wrote:
Quote:That should get you to hull speed at about 2600 RPM, assuming that your engine is happy with that speed. I can't remember what the stock prop pitch was, but 18×11 sounds right.—
Rich Carter
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I believe 20×13 was the original pearson spec. With the newer westerbeke, things may be different (for optimum rpms/crusing speed), but with the old W60s and W58s, it seems like 2000 rpm was more than enough to cruise at 6.5 to 7 knots. At least that’s how my W60 ran with a fixed 20×13.
P
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6.5 to 7 at 2000 rpm, W60, 20 x13 fixed. that’s me too. (1.25 gph mas o menos)
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Rich,
the original was 20×13 and was too much prop..
Now I have the 18 x 9 feathering… but it needs just a wee bit more pitch…Leaving in 5 min for a week on the Chesapeake…
wind and weather at this moment are very good…Rick
Eclipse #73On Fri, Sep 19, 2008 at 1:22 PM, < ([email][/email])> wrote:
Quote:Rick
Have you asked your prop shop to cut it down to 18×13? its bad for an engine if you are over propped.—
Rich Carter
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Er, ehm, I'm not sure what prop I have but my W58 runs 5.8-6.5 kts at 1900 rpm at about 1 gal/hr. It will run 6.8-7.2 kts at 2100 rpm, but burns nearly 2 gal/hr. It's a 3 bladed prop and will run up to about 2800 rpm total.
Does that mean I need to change the prop?
Bob
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Yup. I have my original fixed prop here on a shelf. It’s a 20×13, and was too much prop for my W60. I don’t remembery what you have for an engine. I think this is too big for a W58 too.
I think the problem with these boats is that Pearson didn’t put the right gear reduction in the drive train. From what I can tell, they should have used about a 2.5:1 gear reduction instead of the 2:1. With a 20″ prop and a low pitch, the tip will start to cavitate at high shaft speed. If you go down size and increase pitch, you don’t have enough surface area and the engine starts to burn fuel. You went down in size and decreased pitch. You’ll have to spin this too fast to get any speed. Most feathering props are adjustable. Try 18×12 or 18×13. Someone with the same engine could probably advise.I’ve got an 18.5×12, but I have a different engine and gear reduction.
Rich Carter
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