http://www.bettermarineservices.com/articles/drives.htm
Nice article on alignment, from prop to engine. Good illustrations, too.
Loren
Nice article on alignment, from prop to engine. Good illustrations, too.
Loren
Drive System Maint. article
- Thread starter Loren Beach
- Start date
Maine Sail
Member III
Some good points..
I agree with Tim and ......
While there are some good points I have a hard time taking anyone in the marine business seriously who advises the use of a slide hammer to remove a coupling. Slide hammers should never be used when the coupling is attached to the engine. Do lots of hack mechanics do this? Yes! Does it make it right? NO! There are NO excuses for the use of a slide hammer in this manner and the maker and marketer of them who advises this should have been taken to the pasture and put out of his or her misery long ago!
The bearings in transmissions are not designed to take jarring impacts and blows by a slide hammer and neither are the threads of the prop shaft. They are very easily damaged and ruined even by light blows with a slide hammer..
I wonder how many of his customers have required a tranny rebuild shortly after he used a slide hammer on their boat.
The hard way, as he shows, is the right way if you don't want to do damage to the tranny!!
This is directly from ABYC P-6
6.5.5.3 Bearings, shaft, and couplings shall be aligned to
a tolerance of no more than .004 in. (.102 mm) measured
between the parallel flange of the coupling with the
coupling bolts loose.
6.7 SHAFT SEALS AND SHAFT LOGS
6.5.5.3.1 Alignment shall be accomplished with the boat
floating.
NOTE: Wood and fiberglass vessels may require some
time after launching to reach a point of equilibrium
whereby distortion induced by storage stresses have been
relieved.
I agree with Tim and ......
While there are some good points I have a hard time taking anyone in the marine business seriously who advises the use of a slide hammer to remove a coupling. Slide hammers should never be used when the coupling is attached to the engine. Do lots of hack mechanics do this? Yes! Does it make it right? NO! There are NO excuses for the use of a slide hammer in this manner and the maker and marketer of them who advises this should have been taken to the pasture and put out of his or her misery long ago!
The bearings in transmissions are not designed to take jarring impacts and blows by a slide hammer and neither are the threads of the prop shaft. They are very easily damaged and ruined even by light blows with a slide hammer..
I wonder how many of his customers have required a tranny rebuild shortly after he used a slide hammer on their boat.
The hard way, as he shows, is the right way if you don't want to do damage to the tranny!!
This is directly from ABYC P-6
6.5.5.3 Bearings, shaft, and couplings shall be aligned to
a tolerance of no more than .004 in. (.102 mm) measured
between the parallel flange of the coupling with the
coupling bolts loose.
6.7 SHAFT SEALS AND SHAFT LOGS
6.5.5.3.1 Alignment shall be accomplished with the boat
floating.
NOTE: Wood and fiberglass vessels may require some
time after launching to reach a point of equilibrium
whereby distortion induced by storage stresses have been
relieved.
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Maine Sail
Member III
Tim,
While it may sound like a good idea it is in fact not such a good idea.
A typical 1" or 7/8" shaft will deflect very, very easily to the bolts being under tension. Even finger tight coupling bolts which are usually fine thread is enough to deflect the coupling to throw the alignment off.
The proper way to check alignment is outlined by the ABYC with good reason. On a 4" shaft, that won't deflect easily, it may be ok but the proper method is to check the alignment with the bolts loose not tight while sandwiching two pieces of feeler gauge...
ABYC:
6.5.5.3 Bearings, shaft, and couplings shall be aligned to
a tolerance of no more than .004 in. (.102 mm) measured
between the parallel flange of the coupling with the
coupling bolts loose.
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Slide hammers and hammering output flanges
Here's an internal diagram of the Hurth transmissions many of us have. I have the HBW-10-2R in my E38, on the old heavy block 5432. I just replaced the dripless shaft seal and in the process of putting the shaft and coupling back together I got the key in wrong. I really didn't know there was a wrong way. This is on a straight, square-keyed shaft and coupling. In my ignorance I hammered away on it for a few minutes with a small sledge hammer before giving up and getting some help. Once the key was squared away (only eight ways to try) the coupling slid on really easily, and there was no wiggling or play in the coupling. After the experience of getting the two apart with a coupling puller, I was amazed at how easily they slid together.
Discussing the hammering with the yard manager, he didn't think we hurt anything. I had put a piece of 3/4" plywood between the couplings, but the transmission still absorbed the blows. You can imagine the sinking feeling when I read Maine Sail's critique of the slide hammer causing problems with transmissions.
Today at the boat show I made a point to talk to a transmission repair shop. I am still concerned, and have a plan to evaluate if I did some damage, but I am not as worried as I was since that post. In a nutshell, I was told that the bearings can take a pretty good beating if they were in good shape to begin with (a bit of an unknown) and there was little or no fore and aft play in the output shaft.
He also said that the bearings are regular Timken wheel bearings and are very hard steel. The weak point of either shaft assembly is the aluminum end cap. You can see the input shaft cap with the four bolts in the second attachment. The output shaft cap is inside the bell housing and it could leak if the shaft was shoved forward. That is still a possibility in my case. I will be watching for fluid loss. The evaluation plan is to check the fore-aft play, spin the output shaft to check for roughness, and to watch the fluid level. I suppose when we run it in the slings it could make a lot of noise, too. We have to break in the carbon face of the shaft seal, so we will run in the slings for a while anyway. I have two draw bridges to negotiate to get back to my marina, and every time we go out we have a railroad bridge and a swing bridge to pass, so I am very concerned about drive train or engine problems in our river location.
In addition, before I change the fluid, I take one of those magnet on a stick things and stick it into the fluid and see what kind of metal comes out. I have only gotten a little powder-type residue up til now, so a change to the results of that test would signal damage.
A couple of other tidbits from the mechanic about the Hurth:
-- The lubrication is splash type, so over filling the fluid a little is not going to cause any real problems. There may be some venting out the filler cap, but that is about it. Foaming or air in the fluid isn't particularly a problem. (I think it would be a problem if there was a pump involved, and/or an external heat exchanger)
-- If the transmission starts to delay dropping into gear, or goes into gear with a clunk, time to get it overhauled. Cost these days is $500-$600 USD.
-- The older Hurths are good for about 2000 hours, generally, before the shifting problems start.
-- He brought up the slide hammer removal technique, saying it wouldn't hurt this type of transmission. (We didn't discuss damage to threads on a shaft.)
I don't know this mechanic, can't vouch for him, but he never tried to scare me into giving him any business, so I offer this as a another opinion. I think it is possible to hurt transmissions in this way, but maybe (hopefully) the Hurths aren't so easily bruised. The $169 Vessel Assist membership sounds like a good deal, doesn't it?
Here's an internal diagram of the Hurth transmissions many of us have. I have the HBW-10-2R in my E38, on the old heavy block 5432. I just replaced the dripless shaft seal and in the process of putting the shaft and coupling back together I got the key in wrong. I really didn't know there was a wrong way. This is on a straight, square-keyed shaft and coupling. In my ignorance I hammered away on it for a few minutes with a small sledge hammer before giving up and getting some help. Once the key was squared away (only eight ways to try) the coupling slid on really easily, and there was no wiggling or play in the coupling. After the experience of getting the two apart with a coupling puller, I was amazed at how easily they slid together.
Discussing the hammering with the yard manager, he didn't think we hurt anything. I had put a piece of 3/4" plywood between the couplings, but the transmission still absorbed the blows. You can imagine the sinking feeling when I read Maine Sail's critique of the slide hammer causing problems with transmissions.
Today at the boat show I made a point to talk to a transmission repair shop. I am still concerned, and have a plan to evaluate if I did some damage, but I am not as worried as I was since that post. In a nutshell, I was told that the bearings can take a pretty good beating if they were in good shape to begin with (a bit of an unknown) and there was little or no fore and aft play in the output shaft.
He also said that the bearings are regular Timken wheel bearings and are very hard steel. The weak point of either shaft assembly is the aluminum end cap. You can see the input shaft cap with the four bolts in the second attachment. The output shaft cap is inside the bell housing and it could leak if the shaft was shoved forward. That is still a possibility in my case. I will be watching for fluid loss. The evaluation plan is to check the fore-aft play, spin the output shaft to check for roughness, and to watch the fluid level. I suppose when we run it in the slings it could make a lot of noise, too. We have to break in the carbon face of the shaft seal, so we will run in the slings for a while anyway. I have two draw bridges to negotiate to get back to my marina, and every time we go out we have a railroad bridge and a swing bridge to pass, so I am very concerned about drive train or engine problems in our river location.
In addition, before I change the fluid, I take one of those magnet on a stick things and stick it into the fluid and see what kind of metal comes out. I have only gotten a little powder-type residue up til now, so a change to the results of that test would signal damage.
A couple of other tidbits from the mechanic about the Hurth:
-- The lubrication is splash type, so over filling the fluid a little is not going to cause any real problems. There may be some venting out the filler cap, but that is about it. Foaming or air in the fluid isn't particularly a problem. (I think it would be a problem if there was a pump involved, and/or an external heat exchanger)
-- If the transmission starts to delay dropping into gear, or goes into gear with a clunk, time to get it overhauled. Cost these days is $500-$600 USD.
-- The older Hurths are good for about 2000 hours, generally, before the shifting problems start.
-- He brought up the slide hammer removal technique, saying it wouldn't hurt this type of transmission. (We didn't discuss damage to threads on a shaft.)
I don't know this mechanic, can't vouch for him, but he never tried to scare me into giving him any business, so I offer this as a another opinion. I think it is possible to hurt transmissions in this way, but maybe (hopefully) the Hurths aren't so easily bruised. The $169 Vessel Assist membership sounds like a good deal, doesn't it?
Attachments
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HBW_internal.jpg -
HurthTrans01Top-small.jpg
Maine Sail
Member III
Now you can see the bearings & races. The biggie though is the small bolt #41 holding the output shaft in place!! Many mechanics feel it is safe to use a slide hammer, and they may do fine in some cases, but with a really stuck on coupling that entire ten pound slide is bating the bearing into the races and exerting it's entire force onto that one bolt #41..
You should avoid using a hammer made of a harder metal than the coupling. Using a brass, lead, copper or plastic hammer wil greatly reduce the risk of damage. The wood block however probably absorbed the hard impacts quite well so no worries.
As for couplings they should NEVER just "slide on really easily". The fit of couplings is very, very precise and is often referred to as a light "tap fit" meaning that you should not just be able to slide it on by hand. There is a slight reveal at the inside end of the coupling to allow it to be started but then it should get tight. Anything less than a "light press fit" will lead to movement and can ruin a shaft. Most prop shafting shops recommend a new coupling every time an old one is removed because the layer of rust broken free when removing was your tolerance & fit. You should always do a fit & face after a coupling removal. It usually runs about $35.00 unless your coupling can not be re-used then add a new coupling.. Hamilton Marine has excellent prices on shafting work!!
Checking the run out on the face of a coupling. This one was out less than .25 one thousandths..
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That coupling looks familiar. Thanks for the clarifications and advice.
The idea of a slight interference fit is intuitive for the shaft and coupling. When clean, the fit on mine was smooth and easy. With a little anti-seize applied (and correct key orientation) we had to lean on it to get it to slide on. We did not do any particular cleanup on the shaft or the inside of the coupling. A couple passes with emery cloth. The key was just wiped off. There are two set screws on the coupling that I have to remember to wire up so they don't back out.
I'll ask about a runout check or re-facing, and see what the yard manager says. Maybe they did a runout check, but we didn't talk about facing the coupling. He charged me an hour of labor to find the key orientation and check the shaft-coupling fit, so it's possible he had a runout done. He hasn't recommended I replace the coupling.
The idea of a slight interference fit is intuitive for the shaft and coupling. When clean, the fit on mine was smooth and easy. With a little anti-seize applied (and correct key orientation) we had to lean on it to get it to slide on. We did not do any particular cleanup on the shaft or the inside of the coupling. A couple passes with emery cloth. The key was just wiped off. There are two set screws on the coupling that I have to remember to wire up so they don't back out.
I'll ask about a runout check or re-facing, and see what the yard manager says. Maybe they did a runout check, but we didn't talk about facing the coupling. He charged me an hour of labor to find the key orientation and check the shaft-coupling fit, so it's possible he had a runout done. He hasn't recommended I replace the coupling.
Maine Sail
Member III
Many
Many yard guys unfortunately don't understand about fit of a coupling. If there was rust in there when you removed it re-using it would be a rare situation but not entirely out of the question.
As for never seize try to avoid it's use and instead use a galvanically inert product like Tef-Gel. Graphite, copper or aluminum based anti-seize products can make matters worse on a prop shaft galvanically speaking.
I have been using Tef-Gel for a while with tremendous success. The coupling that I just removed a few weeks ago came off with ZERO rust and can be re-used. It is the coupling in the photo above, after being painted, that is being checked for facing issues.
This is how it came off using Tef-Gel
And the Shaft:
Many yard guys unfortunately don't understand about fit of a coupling. If there was rust in there when you removed it re-using it would be a rare situation but not entirely out of the question.
As for never seize try to avoid it's use and instead use a galvanically inert product like Tef-Gel. Graphite, copper or aluminum based anti-seize products can make matters worse on a prop shaft galvanically speaking.
I have been using Tef-Gel for a while with tremendous success. The coupling that I just removed a few weeks ago came off with ZERO rust and can be re-used. It is the coupling in the photo above, after being painted, that is being checked for facing issues.
This is how it came off using Tef-Gel
And the Shaft:
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