Hi,
For 33 owners, do you know what size and pitch your propeller is, and do you have photographs of your propeller & clearances?
I have been having transmission problems, and one thing I think I need to fix is my propeller clearances, my prop is too far back from the bearing.
My boat has a 2008 Universal 25XPB (25hp, 3000rpm), so the ideal propeller size would be slightly different from the original M30 24hp 2800 max rpm, but I'd be curious to know what prop other 33' owners are using. I have a 14' 9 prop.
Thanks,
Evan
propeller size and clearance on a 33?
Moderator: Jim Walsh
Hey Evan -
Sorry to hear about the tranny problems. What are the symptoms?
This thread has a photo of Zeida's prop and clearances. Mine looks essentially the same (I do have photos, but none uploaded to share at the moment). http://www.capedory.org/board/viewtopic.php?t=26785&
I have the M30 engine and wrote down my prop size somewhere but its not handy either. I want to say it is a 13" prop but i forget the pitch. I imagine you'll find more pics in the archives. Good luck,
Matt
Sorry to hear about the tranny problems. What are the symptoms?
This thread has a photo of Zeida's prop and clearances. Mine looks essentially the same (I do have photos, but none uploaded to share at the moment). http://www.capedory.org/board/viewtopic.php?t=26785&
I have the M30 engine and wrote down my prop size somewhere but its not handy either. I want to say it is a 13" prop but i forget the pitch. I imagine you'll find more pics in the archives. Good luck,
Matt
Interesting, just looking at the picture compared to mine I'd guess Zeida's is a 17". Mine is 14". As you can see my prop is too far back from the bearing, and I'm wondering if that could be what's causing my transmission trouble.
I am on my third transmission, the last two started slipping at around 200 hours, and had burned oil.
My current one, a new ZF 10m, has around 25 hours on it and it already has burned oil. So it would appear they are overheating for some reason.
I've checked the shift linkage, and the alignment and those are apparently fine. I thought I could be slightly over propped, but max engine rpm was reached with the first gear, and the second was very close. I re-pitched my prop anyway, to test the theory. I'll know when I check the oil after a few more hours if that helped.
I'm in Ft Lauderdale, and ZF are helping me look at the problem. I've had two mechanics check it out already, beyond my own research and testing, and they couldn't find anything wrong.
I am on my third transmission, the last two started slipping at around 200 hours, and had burned oil.
My current one, a new ZF 10m, has around 25 hours on it and it already has burned oil. So it would appear they are overheating for some reason.
I've checked the shift linkage, and the alignment and those are apparently fine. I thought I could be slightly over propped, but max engine rpm was reached with the first gear, and the second was very close. I re-pitched my prop anyway, to test the theory. I'll know when I check the oil after a few more hours if that helped.
I'm in Ft Lauderdale, and ZF are helping me look at the problem. I've had two mechanics check it out already, beyond my own research and testing, and they couldn't find anything wrong.
I wonder if you are really that much further back or if the lack of a zinc on your shaft is just making it look that way . . . ? Are you or your mechanics certain the alignment is perfect? Are you wearing out cutlass bearings?
I'm sure others who know far more will chime in but I will post a pic of my prop and the clearance this evening.
Matt
I'm sure others who know far more will chime in but I will post a pic of my prop and the clearance this evening.
Matt
Thanks MFC,
To be honest I'm not sure about the cutless bearings, I don't think so. I haven't checked the drip rate lately, but it is still dry when I'm not moving. Last time I checked while underway it was dripping the right amount and the shaft was not hot afterwards.
I think I have a little over 4" of shaft between bearing and prop. Apparently I should have 1-1.5 times the shaft diameter (1") so 1" or 1.5" would be correct:
http://www.cruisersforum.com/gallery/sh ... ageuser=79
I'm really not sure if this is enough to cause a problem though.
The alignment was not checked with a dial indicator, only visually inspected and inspected with the 'butter knife' method. Between that and the flexible coupling the mechanics I tried so far didn't think alignment was the problem. I want to get a more thorough test done, at higher rpms with a dial indicator. I'm wondering if my mounts could be an issue, or if this prop-bearing distance could matter at higher rpms.
My coupling doesn't support the use of a feeler gauge, it nests inside the drivesaver.
By the way, what was the standard transmission that came with the CD33? From the pictures of Zeida's boat it looks like a Hurth.
To be honest I'm not sure about the cutless bearings, I don't think so. I haven't checked the drip rate lately, but it is still dry when I'm not moving. Last time I checked while underway it was dripping the right amount and the shaft was not hot afterwards.
I think I have a little over 4" of shaft between bearing and prop. Apparently I should have 1-1.5 times the shaft diameter (1") so 1" or 1.5" would be correct:
http://www.cruisersforum.com/gallery/sh ... ageuser=79
I'm really not sure if this is enough to cause a problem though.
The alignment was not checked with a dial indicator, only visually inspected and inspected with the 'butter knife' method. Between that and the flexible coupling the mechanics I tried so far didn't think alignment was the problem. I want to get a more thorough test done, at higher rpms with a dial indicator. I'm wondering if my mounts could be an issue, or if this prop-bearing distance could matter at higher rpms.
My coupling doesn't support the use of a feeler gauge, it nests inside the drivesaver.
By the way, what was the standard transmission that came with the CD33? From the pictures of Zeida's boat it looks like a Hurth.
pic
<a href="https://picasaweb.google.com/lh/photo/c ... site"><img src="https://lh4.googleusercontent.com/-8ad8 ... 520017.JPG" height="480" width="640" /></a>
Note the zinc is not where it should be . . .
But by reference to the shaft tube, your shaft is, indeed, longer and your prop further back. Maybe an inch or so.
<a href="https://picasaweb.google.com/lh/photo/O ... site"><img src="https://lh6.googleusercontent.com/-VK8T ... 520039.JPG" height="480" width="640" /></a>
Another view
Note the zinc is not where it should be . . .
But by reference to the shaft tube, your shaft is, indeed, longer and your prop further back. Maybe an inch or so.
<a href="https://picasaweb.google.com/lh/photo/O ... site"><img src="https://lh6.googleusercontent.com/-VK8T ... 520039.JPG" height="480" width="640" /></a>
Another view
Thanks again MFC,
Through very unscientific means (I zoomed my screen until the prop shaft was actual-size 1" diameter and then measured) My bearing to prop distance is 3.3 inches and yours is 2.25 inches (assuming your shaft is 1" like mine.)
It doesn't seem like that should make much of a difference. Maybe I am barking up the wrong tree.
Through very unscientific means (I zoomed my screen until the prop shaft was actual-size 1" diameter and then measured) My bearing to prop distance is 3.3 inches and yours is 2.25 inches (assuming your shaft is 1" like mine.)
It doesn't seem like that should make much of a difference. Maybe I am barking up the wrong tree.
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JWSutcliffe
- Posts: 301
- Joined: Jul 29th, '08, 22:41
- Location: CD 31 Oryx, hull #55, based in Branford CT
Without knowing what the transmission failure symptoms were for your previous transmissions its hard to speculate, but I would tend to doubt that the propeller location/overhung shaft length is a direct cause for failures. It is more likely that you have an alignment problem.
Despite popular misconceptions, the Drivesaver type coupling inserts are not a flexible coupling in the traditional sense. They are intended only to provide a lower rotational spring rate in order to lessen the shock loading on the transmission clutches during engagement. They do not, however, have the capability to significantly compensate for misalignment of the shaft to the transmission. (I am not "shooting from the hip" in saying this - in my not-boating time I design, specify, sell and train customers in the setup and alignment of engine test system drivelines ranging in speed from 1000 to 30,000 rpm or more.) Nor is the relatively loose fit of the brass/rubber cutless bearings to the shaft a problem with the very short, stiff propeller shafts used in Cape Dories. If the engine mounts are adjusted properly so that the transmission output flange is aligned to the prop shaft, vibration is minimized. If the transmission is not aligned to the shaft, vibration increases and more importantly, the output shaft bearing sees very high loads, leading to premature failure.
Putting a dial indicator on the shaft is not an effective way to determine whether the alignment is correct. A misaligned driveline will still appear to run fairly true at the coupling location, but it will be imposing high loads to the transmission. The only effective way to evaluate the alignment in these boats is to directly measure the gap between the prop shaft flange and transmission flange (or in your case, the elastic coupling insert) at 4 radial positions. Since the typical output shaft on the Hurth transmission is not a continuous face flange, but rather has 4 machined pads which mate to the prop shaft flange (or coupling insert), you need to unbolt the insert from the prop shaft flange, separate them slightly while still keeping the pilot diameter on the prop shaft flange engaged with the insert, and measure the gap at the 4 bolt pads with either a feeler gauge or calipers. If the gaps at all 4 points are not the same, then the engine mounts have to be adjusted laterally and/or vertically until the 4 gaps are all equal within a few thousandths of an inch. It's a slow, tedious process - I know because I am in the middle of doing it myself.
Despite popular misconceptions, the Drivesaver type coupling inserts are not a flexible coupling in the traditional sense. They are intended only to provide a lower rotational spring rate in order to lessen the shock loading on the transmission clutches during engagement. They do not, however, have the capability to significantly compensate for misalignment of the shaft to the transmission. (I am not "shooting from the hip" in saying this - in my not-boating time I design, specify, sell and train customers in the setup and alignment of engine test system drivelines ranging in speed from 1000 to 30,000 rpm or more.) Nor is the relatively loose fit of the brass/rubber cutless bearings to the shaft a problem with the very short, stiff propeller shafts used in Cape Dories. If the engine mounts are adjusted properly so that the transmission output flange is aligned to the prop shaft, vibration is minimized. If the transmission is not aligned to the shaft, vibration increases and more importantly, the output shaft bearing sees very high loads, leading to premature failure.
Putting a dial indicator on the shaft is not an effective way to determine whether the alignment is correct. A misaligned driveline will still appear to run fairly true at the coupling location, but it will be imposing high loads to the transmission. The only effective way to evaluate the alignment in these boats is to directly measure the gap between the prop shaft flange and transmission flange (or in your case, the elastic coupling insert) at 4 radial positions. Since the typical output shaft on the Hurth transmission is not a continuous face flange, but rather has 4 machined pads which mate to the prop shaft flange (or coupling insert), you need to unbolt the insert from the prop shaft flange, separate them slightly while still keeping the pilot diameter on the prop shaft flange engaged with the insert, and measure the gap at the 4 bolt pads with either a feeler gauge or calipers. If the gaps at all 4 points are not the same, then the engine mounts have to be adjusted laterally and/or vertically until the 4 gaps are all equal within a few thousandths of an inch. It's a slow, tedious process - I know because I am in the middle of doing it myself.
Skip Sutcliffe
CD31 Oryx
CD31 Oryx
Thanks for the information Skip.
I'm not sure I understand what you mean when you say "while still keeping the pilot diameter on the prop shaft flange engaged with the insert". By that do you mean keep the shaft flange nested inside the red driversaver coupling.
Also I don't think I'm sure which side of the coupling I should be measuring the gap. I think you mean I should be measuring it at B in this picture, but if so I'm not sure I follow why I should loosen the drivesaver coupling. Sorry, I'm a bit confused!
If there is some misalignment - enough to have the gears fail after 200 hours - would there be anything that I might 'feel' while running the boat? And would the 'butter knife test' (resting a knife on the shaft and feeling for vibration) not detect anything at all? I had been told by a couple of 'mechanics' that the alignment would have to be very obviously off to keep breaking the gears like that. Having read your post I'm wondering if I should have listened. (By the way, the alignment was re-done in September when the second gear was installed. The gear failed 200 hours later, just like the first one.)
The symptoms of my failures were that the gear would slip in forward. When the first one failed, it would engage slowly or not at all, and then slip. When the second one failed it would engage immediately, but slip when revs were increased, until it 'clunked' in at higher revs.
Thanks again, this has been driving me crazy for around a month now.
I'm not sure I understand what you mean when you say "while still keeping the pilot diameter on the prop shaft flange engaged with the insert". By that do you mean keep the shaft flange nested inside the red driversaver coupling.
Also I don't think I'm sure which side of the coupling I should be measuring the gap. I think you mean I should be measuring it at B in this picture, but if so I'm not sure I follow why I should loosen the drivesaver coupling. Sorry, I'm a bit confused!
If there is some misalignment - enough to have the gears fail after 200 hours - would there be anything that I might 'feel' while running the boat? And would the 'butter knife test' (resting a knife on the shaft and feeling for vibration) not detect anything at all? I had been told by a couple of 'mechanics' that the alignment would have to be very obviously off to keep breaking the gears like that. Having read your post I'm wondering if I should have listened. (By the way, the alignment was re-done in September when the second gear was installed. The gear failed 200 hours later, just like the first one.)
The symptoms of my failures were that the gear would slip in forward. When the first one failed, it would engage slowly or not at all, and then slip. When the second one failed it would engage immediately, but slip when revs were increased, until it 'clunked' in at higher revs.
Thanks again, this has been driving me crazy for around a month now.
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JWSutcliffe
- Posts: 301
- Joined: Jul 29th, '08, 22:41
- Location: CD 31 Oryx, hull #55, based in Branford CT
Based on your failure mode description, it sounds less likely that alignment is the root cause. However, verifying correct alignment is an important step in ruling out the several possible causes of failure. Probably the clearest way to measure the alignment is to unbolt and remove the drivesaver, slide the shaft and flange forward until it just starts to engage with the pilot on the transmission flange, and measure the gaps at the 4 bolt pads at location B in your picture. Once you have verified correct alignment, reinstall the drivesaver.
There are two other items that I would consider.
1. Has the torsional damper been replaced? This is the flex plate bolted to the flywheel that that the transmission input shaft engages with. The torsional damper has a set of springs that reduce the torsional shock load when the transmission is engaged. Over time these springs can crack or collapse, which dramatically increases the shock loading on the transmission gears and clutches. The torsional damper should be replaced when the transmission is replaced.
2. Have you verified that the shifting cable is correctly adjusted? The Hurth and other similar transmissions have internal clutches. If the shift cable is not correctly adjusted, it may not be fully engaging the clutches. This will result in excessive heat generation and rapid wear. Disconnect the shift cable at the transmission lever end and measure how far the lever on the transmission travels from neutral to forward and neutral to reverse. Then reconnect the cable and verify that the lever at the transmission travels as far when you shift from the pedestal lever.
Good luck with troubleshooting.
There are two other items that I would consider.
1. Has the torsional damper been replaced? This is the flex plate bolted to the flywheel that that the transmission input shaft engages with. The torsional damper has a set of springs that reduce the torsional shock load when the transmission is engaged. Over time these springs can crack or collapse, which dramatically increases the shock loading on the transmission gears and clutches. The torsional damper should be replaced when the transmission is replaced.
2. Have you verified that the shifting cable is correctly adjusted? The Hurth and other similar transmissions have internal clutches. If the shift cable is not correctly adjusted, it may not be fully engaging the clutches. This will result in excessive heat generation and rapid wear. Disconnect the shift cable at the transmission lever end and measure how far the lever on the transmission travels from neutral to forward and neutral to reverse. Then reconnect the cable and verify that the lever at the transmission travels as far when you shift from the pedestal lever.
Good luck with troubleshooting.
Skip Sutcliffe
CD31 Oryx
CD31 Oryx
Thanks again,
That's very clear.
ZF sent two technicians out to me today. They checked the shifting on the gear, and then with the cable. They said the shifting distances were ok. Reverse was a little close to spec, but forward was fine.
They didn't really know what might be causing the problem, but suggested I check the mounts and alignment.
There is quite a lot of vibration at low revs on the engine, so I will also adjust my idle to a higher rpm. The ZF guys suggested that this could be a factor (although I've been careful not to leave it running at low RPMs since I put this latest gear in)
Evan
That's very clear.
ZF sent two technicians out to me today. They checked the shifting on the gear, and then with the cable. They said the shifting distances were ok. Reverse was a little close to spec, but forward was fine.
They didn't really know what might be causing the problem, but suggested I check the mounts and alignment.
There is quite a lot of vibration at low revs on the engine, so I will also adjust my idle to a higher rpm. The ZF guys suggested that this could be a factor (although I've been careful not to leave it running at low RPMs since I put this latest gear in)
Evan