My CD36 came with a 15x14. Is this the most common size for CD36?
I need to replace the original. Thanks, Al North
anorth@mindspring.com
prop for CD36
Moderator: Jim Walsh
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Jeff Barnes
Re: prop for CD36
Al:
The manual for the CD36 specifies a 15X14 3 bladed prop. This was
originally supplied from Essex Machine.
Jeff
jbarnes@oxbio.com
The manual for the CD36 specifies a 15X14 3 bladed prop. This was
originally supplied from Essex Machine.
Jeff
jbarnes@oxbio.com
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matt cawthorne
Re: prop for CD36
Al,
The prop that Essex will sell you is a Michigan Wheel 15RH14-sailor style made of a heavily zinc loaded "bronze". With the 15RH-14 you will not be able to achieve the maximum power out of your Perkins 4.108 engine if it has the 2:1 gearbox. I had mine re-pitched to 15RH12. I have to run the engine at higher RPMs, but I now get more thrust capability when punching into head seas. It is a trade-off. I bought a new 15RH12 a few years ago because the previous owner had left the zinc off and it looked like a leopard. On top of that my zinc fell off the second year I owned the boat and the leopard look got worse. The spotting is a sign of de-zincification which means that it has degraded strength. If I had it to do over I would have had the thing cast out of a bronze with no zinc in it.
Matt
mcawthor@bellatlantic.net
The prop that Essex will sell you is a Michigan Wheel 15RH14-sailor style made of a heavily zinc loaded "bronze". With the 15RH-14 you will not be able to achieve the maximum power out of your Perkins 4.108 engine if it has the 2:1 gearbox. I had mine re-pitched to 15RH12. I have to run the engine at higher RPMs, but I now get more thrust capability when punching into head seas. It is a trade-off. I bought a new 15RH12 a few years ago because the previous owner had left the zinc off and it looked like a leopard. On top of that my zinc fell off the second year I owned the boat and the leopard look got worse. The spotting is a sign of de-zincification which means that it has degraded strength. If I had it to do over I would have had the thing cast out of a bronze with no zinc in it.
Matt
mcawthor@bellatlantic.net
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Mike Thorpe
Re: prop for CD36
Al,
I recently went through this with my CD-36. A 15x14 prop was on the boat when I purchased her. One thing that I noticed was that max speed was achieved at 2000 -2100 RPM. Perkins says the engine should be run at 2500 RPM's. However, any additional throttle on my part only resulted in the boat trying to bury her stern.
I further complicated the problem when I added a high output alternator thus lowereing the productive RPM's even further. Also, the engine wasn't burning all of it's fuel at this lower RPM rate resulting in a residue of unburned fuel accumulating on the transom.
I had the prop calculations redone by H&H Prop. here in Massachusetts. The results were that a 15x11 prop was required but that the max allowable pitch change was 2. They said the best alternative other than buying a new prop was to repitch the 15x14 to 15x12 and see how it went. I had this done this winter and next summer will be the test.
Below is a link to Michigan Wheel where they will calculate the proper pitch. If you plan on buying a new prop take into consideration any future loads you plan for the engine.
Hope this helps.
Mike Thorpe
CD-36 Journey's End
Hyannis, MA
mthorpe@capecod.net
I recently went through this with my CD-36. A 15x14 prop was on the boat when I purchased her. One thing that I noticed was that max speed was achieved at 2000 -2100 RPM. Perkins says the engine should be run at 2500 RPM's. However, any additional throttle on my part only resulted in the boat trying to bury her stern.
I further complicated the problem when I added a high output alternator thus lowereing the productive RPM's even further. Also, the engine wasn't burning all of it's fuel at this lower RPM rate resulting in a residue of unburned fuel accumulating on the transom.
I had the prop calculations redone by H&H Prop. here in Massachusetts. The results were that a 15x11 prop was required but that the max allowable pitch change was 2. They said the best alternative other than buying a new prop was to repitch the 15x14 to 15x12 and see how it went. I had this done this winter and next summer will be the test.
Below is a link to Michigan Wheel where they will calculate the proper pitch. If you plan on buying a new prop take into consideration any future loads you plan for the engine.
Hope this helps.
Mike Thorpe
CD-36 Journey's End
Hyannis, MA
Al North wrote: My CD36 came with a 15x14. Is this the most common size for CD36?
I need to replace the original. Thanks, Al North
mthorpe@capecod.net
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Bob Grabham
Re: prop for CD36
Al - That's what is on my CD36 now and I've not experienced any of the problems previously mentioned. When the bottom is clean I can get over 3000 rpm at max throttle and have no problem cruising all day long in the 2500 rpm range. Here in the Chesapeake we had a fairly typical year last year with regard to bottom growth. Since I have yet to apply Captain Stump's stove black to the prop, I accumulated a pretty good growth of barnacles. Diving on the boat about every 2-3 months seems to keep the most of them under control. Also, I run the engine in reverse for about a half an hour at the dock at low rpms just to keep water flowing over the bottom. That, of course, is only on those few weekends when the boat doesn't go out for a sail. I've got the Perkins 4-108 with a 2:1 reduction to the prop. Good luck.
Bob Grabham
CD-36, #140
Hunky Dory
Topping, Virginia (8 miles NW of the mouth of the Rappahannock)
grabhamb@chesterfield.gov
Bob Grabham
CD-36, #140
Hunky Dory
Topping, Virginia (8 miles NW of the mouth of the Rappahannock)
grabhamb@chesterfield.gov
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Patrick Turner
Re: prop for CD36
Al,
I'm must be the only exception in this group of CD36 owners, but on my boat (which admitadly is one of the first CD36's #2) there isn't room for a proper installation of a 15" prop. For proper clearance around the prop you need a distance from the blade to the hull/rudder that equals a certain percentage of the prop diameter. On a 15" prop that works out to about 2.1" of clearance all around. I don't have that space from the top of the prop aperture to the tip of the prop blade on a 15" prop. So I went with a 14" prop pitched at 10d. I cruise and reach hull speed (in calm seas) at 2400rpm and have a max rpm of 3000 which is the limit on my Universal 40hp engine. Perhaps they changed the stern tube on later models....there is room for it, but if your boat is out of the water measure the distance all around you prop now and see what you have.
Pat
patrick.t@attbi.com
I'm must be the only exception in this group of CD36 owners, but on my boat (which admitadly is one of the first CD36's #2) there isn't room for a proper installation of a 15" prop. For proper clearance around the prop you need a distance from the blade to the hull/rudder that equals a certain percentage of the prop diameter. On a 15" prop that works out to about 2.1" of clearance all around. I don't have that space from the top of the prop aperture to the tip of the prop blade on a 15" prop. So I went with a 14" prop pitched at 10d. I cruise and reach hull speed (in calm seas) at 2400rpm and have a max rpm of 3000 which is the limit on my Universal 40hp engine. Perhaps they changed the stern tube on later models....there is room for it, but if your boat is out of the water measure the distance all around you prop now and see what you have.
Pat
patrick.t@attbi.com
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Tom Blanchard
Re: prop for CD36
Al, the prop that came on my CD36 #44 is also a 15x14. I'm getting ready to add a high output alternator, so based on other comments, I'll see how it does. Last season (my first with the boat) it cruised easily at 2500, although a bad shaft bearing limited that. My CD owner's manual specified 15x15.Al North wrote: My CD36 came with a 15x14. Is this the most common size for CD36?
I need to replace the original. Thanks, Al North
tblanchard@empire.state.ny.us