I have a 1979 CD36 and I can only fit a 14" prop in the aperture. I have noticed on doing a search that alot of other CD36'ers managed to put a 15" prop in and I wondered if anybody was aware of a change in the aperture design on these boats? I have not personally measured the distance myself, but the diver that took the old prop off and put the new one on said that there was just under 2" of air between the blade tip and the top of the aperture. That's just barely adequate for 14" let alone 15".
Any comments?
Pat
patrick.t@home.com
CD36 and prop aperture
Moderator: Jim Walsh
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Ken Coit
Re: CD36 and prop aperture
Pat,
I believe that Parfait carries a prop that is stamped 15R14; whether it has been re-pitched, I don't know. I have never measured the clearance, but it isn't visually distressing. Liz Robinson indicated back in 98 that Michigan Wheel says the clearance should be at least 15% of the prop diameter. That would be 2 1/4 inches for the 15 and 2 1/10 inches for the 14.
I found a close up photo of Parfait's prop. It looks like the 15 inch prop is in an 18 inch aperture, giving a clearance of only 1 1/2 inches to the hull and the rudder. We have vibrations above 2200 RPM and this may be why. Let me know if you'd like to see the photo, barnacles and all, and I will scan it and ship a jpeg copy to you.
I have submitted a form to Michigan Wheel for analysis. They seem to be busy and are predicting 7 to 10 days for their work. I'll share what I get. If you want to do your own thing see the link below.
Sailing season is here, where are you?
Ken
parfait@nc.rr.com
I believe that Parfait carries a prop that is stamped 15R14; whether it has been re-pitched, I don't know. I have never measured the clearance, but it isn't visually distressing. Liz Robinson indicated back in 98 that Michigan Wheel says the clearance should be at least 15% of the prop diameter. That would be 2 1/4 inches for the 15 and 2 1/10 inches for the 14.
I found a close up photo of Parfait's prop. It looks like the 15 inch prop is in an 18 inch aperture, giving a clearance of only 1 1/2 inches to the hull and the rudder. We have vibrations above 2200 RPM and this may be why. Let me know if you'd like to see the photo, barnacles and all, and I will scan it and ship a jpeg copy to you.
I have submitted a form to Michigan Wheel for analysis. They seem to be busy and are predicting 7 to 10 days for their work. I'll share what I get. If you want to do your own thing see the link below.
Sailing season is here, where are you?
Ken
Patrick Turner wrote: I have a 1979 CD36 and I can only fit a 14" prop in the aperture. I have noticed on doing a search that alot of other CD36'ers managed to put a 15" prop in and I wondered if anybody was aware of a change in the aperture design on these boats? I have not personally measured the distance myself, but the diver that took the old prop off and put the new one on said that there was just under 2" of air between the blade tip and the top of the aperture. That's just barely adequate for 14" let alone 15".
Any comments?
parfait@nc.rr.com
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Ken Coit
Re: CD36 and prop aperture
The CD/36 manual calls for a 15R14 prop. I wonder if the Robinhood 36 uses the same prop and aperture? Michigan Wheel recommends 15% of diameter as clearance. That would be 2.25 inches where Parfait has about 1.5 inches.
Ken
parfait@nc.rr.com
Ken
Ken Coit wrote: Pat,
I believe that Parfait carries a prop that is stamped 15R14; whether it has been re-pitched, I don't know. I have never measured the clearance, but it isn't visually distressing. Liz Robinson indicated back in 98 that Michigan Wheel says the clearance should be at least 15% of the prop diameter. That would be 2 1/4 inches for the 15 and 2 1/10 inches for the 14.
I found a close up photo of Parfait's prop. It looks like the 15 inch prop is in an 18 inch aperture, giving a clearance of only 1 1/2 inches to the hull and the rudder. We have vibrations above 2200 RPM and this may be why. Let me know if you'd like to see the photo, barnacles and all, and I will scan it and ship a jpeg copy to you.
I have submitted a form to Michigan Wheel for analysis. They seem to be busy and are predicting 7 to 10 days for their work. I'll share what I get. If you want to do your own thing see the link below.
Sailing season is here, where are you?
Ken
Patrick Turner wrote: I have a 1979 CD36 and I can only fit a 14" prop in the aperture. I have noticed on doing a search that alot of other CD36'ers managed to put a 15" prop in and I wondered if anybody was aware of a change in the aperture design on these boats? I have not personally measured the distance myself, but the diver that took the old prop off and put the new one on said that there was just under 2" of air between the blade tip and the top of the aperture. That's just barely adequate for 14" let alone 15".
Any comments?
parfait@nc.rr.com
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Warren Stringer
Re: CD36 and prop aperture
Robinhood just repowered Eendracht, CD 36, 1981, with a 40 hp, three cylinder Yanmar and a 15x15 prop. They just ran a prop evaluation and felt the boat was moderately over-propped, but this gives a lot of reserve power for headwinds and waves.Ken Coit wrote: The CD/36 manual calls for a 15R14 prop. I wonder if the Robinhood 36 uses the same prop and aperture? Michigan Wheel recommends 15% of diameter as clearance. That would be 2.25 inches where Parfait has about 1.5 inches.
Warren
wwtringer@aristotle.net
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Mike Thorpe
Re: CD36 and prop aperture-related question
I have a 1987 CD-36 with the original Perkins 4108-M. Last winter I replaced the standard alternator with a Balmar 150A alternator. The alternator is great however the additional load on the engine has created a problem. The transom is covered with a black residue from unburned deisel fuel. My understanding of this problem is that the engine is not reving high enough to burn the fuel being supplied by the injection pump. I'm told that the soution to this is to take some pitch out of the prop which will allow the engine to rev higher.
The question is how much? Has anybody out there run into the same problem?
Thanks,
Mike
CD-36 Journey's End
1979 CD36 and I can only fit a 14" prop in the aperture. I have noticed on doing a search that alot of other CD36'ers managed to put a 15" prop in and I wondered if anybody was aware of a change in the aperture design on these boats? I have not personally measured the distance myself, but the diver that took the old prop off and put the new one on said that there was just under 2" of air between the blade tip and the top of the aperture. That's just barely adequate for 14" let alone 15".
mthorpe@capecod.net
The question is how much? Has anybody out there run into the same problem?
Thanks,
Mike
CD-36 Journey's End
1979 CD36 and I can only fit a 14" prop in the aperture. I have noticed on doing a search that alot of other CD36'ers managed to put a 15" prop in and I wondered if anybody was aware of a change in the aperture design on these boats? I have not personally measured the distance myself, but the diver that took the old prop off and put the new one on said that there was just under 2" of air between the blade tip and the top of the aperture. That's just barely adequate for 14" let alone 15".
Patrick Turner wrote: Any comments?
Pat
mthorpe@capecod.net
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Larry DeMers
Re: CD36 and prop aperture-related question
You can depitch that prop, certainly, but be aware of the consequences. The black smoke is a too rich mixture being injected into the cylinders..it's basicly a problem of too much fuel as you say, and too few horses available. That 150 A alt. is too big for the engine. My 80A Balmar on my MD7B takes roughly 3hp. This is by far, a larger load than it will ever see in ordinary motoring (not beating into a nasty chop), as evidenced by the sound of the engine working to power that Balmar around. So with your 150A alt., you are using probably 6-7 hp total for that purpose. How many does that engine have new? How many does it have left? You may be taking a significant proportion of the available power, leaving an insufficient amount for powering the boat. When you add in the prop load, you are over loading the engine as it stands.
Valve timing and injector timing and setup may help here. But in the end, you may be forced to step back to the 100A Balmar.
What size are your battery banks? A large alternator may sound like a good deal on the surface, but if the banks are sized too small for the charging capacity, there can be problems with battery life, boiling etc. You may not need that 150A monster anyway..and may be able to downsize a little on the alt. and save an engine rebuild for later (soon it sounds like).
Depitching the prop will cause you to run a higher rpm for the same boat speed..because you are now giving more HP to the alternator for that 30 or 45 minute recharge time. Meanwhile you will be constantly saddled with a slower motoring, lower power engine (at the same rpm), which will cause you to use a higher rpm setting, weraing out your engine faster, and burning thru more fuel in the process. I would nto do this, since that engine is all that stands between you and trouble, should the winds fail.
Good Luck,
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~Sailing Lake Superior~~
demers@sgi.com
Valve timing and injector timing and setup may help here. But in the end, you may be forced to step back to the 100A Balmar.
What size are your battery banks? A large alternator may sound like a good deal on the surface, but if the banks are sized too small for the charging capacity, there can be problems with battery life, boiling etc. You may not need that 150A monster anyway..and may be able to downsize a little on the alt. and save an engine rebuild for later (soon it sounds like).
Depitching the prop will cause you to run a higher rpm for the same boat speed..because you are now giving more HP to the alternator for that 30 or 45 minute recharge time. Meanwhile you will be constantly saddled with a slower motoring, lower power engine (at the same rpm), which will cause you to use a higher rpm setting, weraing out your engine faster, and burning thru more fuel in the process. I would nto do this, since that engine is all that stands between you and trouble, should the winds fail.
Good Luck,
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~Sailing Lake Superior~~
Mike Thorpe wrote:
I have a 1987 CD-36 with the original Perkins 4108-M. Last winter I replaced the standard alternator with a Balmar 150A alternator. The alternator is great however the additional load on the engine has created a problem. The transom is covered with a black residue from unburned deisel fuel. My understanding of this problem is that the engine is not reving high enough to burn the fuel being supplied by the injection pump. I'm told that the soution to this is to take some pitch out of the prop which will allow the engine to rev higher.
The question is how much? Has anybody out there run into the same problem?
Thanks,
Mike
CD-36 Journey's End
1979 CD36 and I can only fit a 14" prop in the aperture. I have noticed on doing a search that alot of other CD36'ers managed to put a 15" prop in and I wondered if anybody was aware of a change in the aperture design on these boats? I have not personally measured the distance myself, but the diver that took the old prop off and put the new one on said that there was just under 2" of air between the blade tip and the top of the aperture. That's just barely adequate for 14" let alone 15".
Patrick Turner wrote: Any comments?
Pat
demers@sgi.com
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matt cawthorne
Cause and effect?
Mike,
You have linked the alternator with the soot problem. Might it just be coincidence? It could be that you have an injector that is dribbling, lots of barnacles on your prop, or some other unrelated problem. Unless you have a huge battery bank it is not likely that the alternator is producing 150 amps for very long. The rest of the time it is mostly unloaded and would not be a problem. I have a suggestion. Depending on the type of voltage regulator you have you may be able to limit the amount of current that the alternator produces. I know that my Balmar (ARS-3?) has this current limiting capability. Read the manual, set it to something like 80 amps, clean your transom and watch it for a while.
I have the Perkins 4.108M and chose to de-pitch the prop to 15-RH-12 instead of the 14 inch pitch it originally had. Yes, I do run the engine a little faster now, but I can get more power out of the engine than I could with the old pitch. More power translates to more thrust to get me out of a tight situation in a pinch. At any rate, the 100 amp alternator works just fine with the 4.108 and a 12 pitch prop. In fact I seem to get less soot now than I did with the stock alternator.
Matt
mcawthor@bellatlantic.net
You have linked the alternator with the soot problem. Might it just be coincidence? It could be that you have an injector that is dribbling, lots of barnacles on your prop, or some other unrelated problem. Unless you have a huge battery bank it is not likely that the alternator is producing 150 amps for very long. The rest of the time it is mostly unloaded and would not be a problem. I have a suggestion. Depending on the type of voltage regulator you have you may be able to limit the amount of current that the alternator produces. I know that my Balmar (ARS-3?) has this current limiting capability. Read the manual, set it to something like 80 amps, clean your transom and watch it for a while.
I have the Perkins 4.108M and chose to de-pitch the prop to 15-RH-12 instead of the 14 inch pitch it originally had. Yes, I do run the engine a little faster now, but I can get more power out of the engine than I could with the old pitch. More power translates to more thrust to get me out of a tight situation in a pinch. At any rate, the 100 amp alternator works just fine with the 4.108 and a 12 pitch prop. In fact I seem to get less soot now than I did with the stock alternator.
Matt
mcawthor@bellatlantic.net
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matt cawthorne
Re: CD36 and prop aperture
Pat,
When I first bought my 1982 cd-36 I measured the tip clearance and I seem to remember that it was less than what was recommended in Dave Gerr's "Propeller Handbook" with the 15 inch prop.
matt
mcawthor@bellatlantic.net
When I first bought my 1982 cd-36 I measured the tip clearance and I seem to remember that it was less than what was recommended in Dave Gerr's "Propeller Handbook" with the 15 inch prop.
matt
mcawthor@bellatlantic.net
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matt cawthorne
Re: CD36 and prop aperture
Warren,
Can your engine attain it's rated rpm? The appropriate pitch depends on the transmission gear ratio. If you can not reach your rated rpm then you will have LESS capability in wind and waves because you will not be able to get the full power from your engine. Check out "Propeller Handbook" by Dave Gerr.
Matt
mcawthor@bellatlantic.net
Can your engine attain it's rated rpm? The appropriate pitch depends on the transmission gear ratio. If you can not reach your rated rpm then you will have LESS capability in wind and waves because you will not be able to get the full power from your engine. Check out "Propeller Handbook" by Dave Gerr.
Matt
mcawthor@bellatlantic.net
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Mike Thorpe
Matt, Larry more info for consideration
Matt, Larry,
First of all thanks for your responses. Here is some more information along with answers to the questions you have asked.
Journey's End is on the hard, the prop was clean when she came out. Before adding the new alternator and other goodies last winter I didn't have this soot problem. I did have a problem keeping my old batteries charged. If the engine wasn't running the auto pilot would take them down very quickly.
I was planning to add an elecric windlass and radar last winter (I did) and refrigeration this coming winter. (I will and it's something I would like to talk to both of you about.)
So last winter I replaced the (2)grp 27's with (4)Grp 27 AGM batteries, (3) house and (1) start. In total 800A reserve capacity. I also added the Balmar 150A alternator and a smart charger.
The engine doesn't have any problem pushing the boat to hull speed in fact at about 2300rpm's I start to bury the transom. The maximum RPM's I can get out of the engine is 2900 at which point the engine exhaust is under water. The Perkins owners manual is on the boat but I seem to remember a max engine RPM of 3500?? Unfortunately I never checked what the maximum engine RPM's were before I changed aternators.
Also, now that I think of it, I don't know what the current pitch is on my prop. Something I will have to check.
Does this additional information help in any way?
Mike
mthorpe@capecod.net
First of all thanks for your responses. Here is some more information along with answers to the questions you have asked.
Journey's End is on the hard, the prop was clean when she came out. Before adding the new alternator and other goodies last winter I didn't have this soot problem. I did have a problem keeping my old batteries charged. If the engine wasn't running the auto pilot would take them down very quickly.
I was planning to add an elecric windlass and radar last winter (I did) and refrigeration this coming winter. (I will and it's something I would like to talk to both of you about.)
So last winter I replaced the (2)grp 27's with (4)Grp 27 AGM batteries, (3) house and (1) start. In total 800A reserve capacity. I also added the Balmar 150A alternator and a smart charger.
The engine doesn't have any problem pushing the boat to hull speed in fact at about 2300rpm's I start to bury the transom. The maximum RPM's I can get out of the engine is 2900 at which point the engine exhaust is under water. The Perkins owners manual is on the boat but I seem to remember a max engine RPM of 3500?? Unfortunately I never checked what the maximum engine RPM's were before I changed aternators.
Also, now that I think of it, I don't know what the current pitch is on my prop. Something I will have to check.
Does this additional information help in any way?
Mike
mthorpe@capecod.net
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Patrick Turner
Re: CD36 and prop aperture
Dave Perry at Robinhood Marine has emailed me back that he doesn't believe there were any changes made to the aperture from year to year, and that he confirmed that there is 2" of clearance between the propeller tip on a 15" prop and the top of the aperture by personally measuring 2 boats they have out on in the yard now. It is possible that the early boats with the Volvo may have had a stern tube that was mounted a little different for the engine and that might account for the difference.
Pat
patrick.t@home.com
Pat
patrick.t@home.com
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matt cawthorne
Re: Matt, Larry more info for consideration
Mike,
Do you actually see black smoke during operation? If so, what rpm does it appear at?
The rpm numbers sound familiar. Prior to my re-pitching the prop the boat reached 7.0 knots at 2500 rpm. The engine maxed out at 2600 rpm with black smoke. When I re-pitched it to a 12 pitch the boat was able to make 7.5 knots at 2980 rpm. I calibrated the tachometer for these measurements, but simply used the boats knotmeter for the speed. Somewhere I have a sheet that lists the maximum cruising rpm for the 4.108m at 4000 rpm. I would have to be in fear of loosing my boat or my life to run the engine above 3500. I could not bring myself to take it above that while calibrating the tach.
Next season try dropping the charging current using your smart regulator. If that does not fix it then it is not your alternator.
Matt
mcawthor@bellatlantic.net
Do you actually see black smoke during operation? If so, what rpm does it appear at?
The rpm numbers sound familiar. Prior to my re-pitching the prop the boat reached 7.0 knots at 2500 rpm. The engine maxed out at 2600 rpm with black smoke. When I re-pitched it to a 12 pitch the boat was able to make 7.5 knots at 2980 rpm. I calibrated the tachometer for these measurements, but simply used the boats knotmeter for the speed. Somewhere I have a sheet that lists the maximum cruising rpm for the 4.108m at 4000 rpm. I would have to be in fear of loosing my boat or my life to run the engine above 3500. I could not bring myself to take it above that while calibrating the tach.
Next season try dropping the charging current using your smart regulator. If that does not fix it then it is not your alternator.
Matt
mcawthor@bellatlantic.net
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Ken Coit
Re: CD36 and prop aperture
Many thanks to Dave Perry and Robinhood. I guess that is another item for our haul out list.
Ken
parfait@nc.rr.com
Ken
Patrick Turner wrote: Dave Perry at Robinhood Marine has emailed me back that he doesn't believe there were any changes made to the aperture from year to year, and that he confirmed that there is 2" of clearance between the propeller tip on a 15" prop and the top of the aperture by personally measuring 2 boats they have out on in the yard now. It is possible that the early boats with the Volvo may have had a stern tube that was mounted a little different for the engine and that might account for the difference.
Pat
parfait@nc.rr.com
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Ken Coit
Re: CD36 and prop aperture
I heard from Michigan Wheel today that 10% of the diameter may be enough clearance and that the difference is likely to be noise, not vibration. I thought they went together, but who am I to question the experts. There is certainly noise. I need to supply them with a bit more info before they will quote a proper prop.
Ken
parfait@nc.rr.com
Ken
matt cawthorne wrote: Pat,
When I first bought my 1982 cd-36 I measured the tip clearance and I seem to remember that it was less than what was recommended in Dave Gerr's "Propeller Handbook" with the 15 inch prop.
matt
parfait@nc.rr.com
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Warren Stringer
Re: CD36 and prop aperture
Good point. Max. loaded RPM was about 250 RPM below max. rated continuous. Given that we were reaching close to hull speed well below that, and have no inclination to put up with that much noise, there is not much incentive to change.matt cawthorne wrote: Warren,
Can your engine attain it's rated rpm? The appropriate pitch depends on the transmission gear ratio. If you can not reach your rated rpm then you will have LESS capability in wind and waves because you will not be able to get the full power from your engine. Check out "Propeller Handbook" by Dave Gerr.
Matt
Warren
wstringer@aristotle.net