Failed Cutlass Bearing

[rms95835]

Our 2010 Jeanneau 42i had the P bracket (prop strut) replaced about 1 year ago. All was well, up until we had to leave the boat in the DR in May of last year. Upon returning, and transiting from Puerto Plata to Samana, the cutlass bearing has failed. There is slop approaching 1/8th of an inch on the prop shaft. There are about 60 hours run time since the parts were replaced, so trying to figure out why a part that typically lasts years, has failed so quickly. My only thought after diving the boat and diagnosing the failure is the line cutter that is installed between the prop and the P bracket is mounted too close to the P bracket and is not allowing water to flow through the cutlass bearing and provide lubrication. Any thoughts would be greatly appreciated, as I would like to prevent this situation from occurring again.

[Paul L]

The strut is not aligned properly, possibly.

[rms95835]

Well I hope a misaligned strut is not the issue, as that certainly will require hauling for a fix. Currently at Puerto Bahia in the DR. Was planning to cross the Mona Passage today as had an appropriate weather window, so will have to check again once repairs are completed. Local mechanic has a plan to pull the old bearing while in the water, replace with new, then re-install the prop. I'm thinking given the condition, and the chance it may be restricting flow, to tell him to leave the line cutter off the shaft.

[Cheechako]

I'm thinking alignment too. Water flow not an issue. Cutlass bearings in full keel boats with only one end open to the water even last for many years. Or...Is it possible the replacement bearing was over size ID to start with? (wrong bearing) Is it possible the strut is loose by any chance? Is the bearing turning in the strut?

[Cheechako]

Originally Posted by rms95835

Well I hope a misaligned strut is not the issue, as that certainly will require hauling for a fix. Currently at Puerto Bahia in the DR. Was planning to cross the Mona Passage today as had an appropriate weather window, so will have to check again once repairs are completed. Local mechanic has a plan to pull the old bearing while in the water, replace with new, then re-install the prop. I'm thinking given the condition, and the chance it may be restricting flow, to tell him to leave the line cutter off the shaft.

Does the boat have an additional bearing in the packing tube? If not, you don't necessarily have to remove the strut, realign the engine instead.


I just thought of something else. You say the boat sat in the DR for a while right? It's very possible the shaft inside the cutlass grooves grew small sharp barnacles, when you started using it again the barnacles tore up the rubber fast. I'm leaning toward this... the DR was terrible for barnacles, especially Luperon Harbor. My cat was there for 5 weeks. Preparing to leave I bet we scraped off enough barnacles to fill 2 five gallon buckets... I'm serious.

[rms95835]

Originally Posted by Cheechako

Does the boat have an additional bearing in the packing tube? If not, you don't necessarily have to remove the strut, realign the engine instead.

I do not believe there is an additional bearing in the packing gland, and that is another issue I'm having, perhaps related. At rest, the boat is completely dry, when the prop shaft is turning, I'm getting way more than the normal amount of water through the shaft seal. There is a rubber boot between the hull and shaft, aft of the coupling on the transmission, and as I'm not sure what type of shaft seal I have, I have not tried to remove. Assuming I can disconnect the coupling and follow standard alignment procedures to correct the possibility of misalignment being the issue?

[Suijin]

Why did you have the P bracket replaced? Collision? It came loose? What?

I'm going to bet that the premature failure of the cutlass is related. Either there is runout in the shaft or the P bracket was not aligned properly, or both.

The cutlass and the P bracket and the alignment of the coupling act as a system. The fact that the P bracket was replaced a year ago would point to it, or associated damage caused originally, being the problem.

[rms95835]

The p bracket was replaced after a pre purchase survey discovered corrosion due to improper grounding/bonding, so to my knowledge, there was not an alignment issue. The prop seemed to run smoothly during sea trials. Was a structural issue with the p bracket. Sounding to me like I need to wait until the bearing has been replaced, then check alignment.

[Cheechako]

Originally Posted by rms95835

I do not believe there is an additional bearing in the packing gland, and that is another issue I'm having, perhaps related. At rest, the boat is completely dry, when the prop shaft is turning, I'm getting way more than the normal amount of water through the shaft seal. There is a rubber boot between the hull and shaft, aft of the coupling on the transmission, and as I'm not sure what type of shaft seal I have, I have not tried to remove. Assuming I can disconnect the coupling and follow standard alignment procedures to correct the possibility of misalignment being the issue?

Hard to say, if the Rubber boot is actually a hose, then you may have a standard packing gland that should be redone. If it's a bellows or etc maybe a dripless seal?
It sounds like you need to open things up, inspect the shaft inside the packing as well as the cutlass, align the engine with new cutlass, repack and should be good to go. Sounds frustrating.
Just a caution, sometimes shafts corrode inside the packing if left to sit damp and wet. The lack of oxygen corrodes the SS shaft. This would require shaft replacement or you will just tear up new packing.

[Paul L]

Originally Posted by rms95835

The p bracket was replaced after a pre purchase survey discovered corrosion due to improper grounding/bonding, so to my knowledge, there was not an alignment issue. The prop seemed to run smoothly during sea trials. Was a structural issue with the p bracket. Sounding to me like I need to wait until the bearing has been replaced, then check alignment.

When the new strut was mounted it needs to be in alignment with the engine. Then the final alignment is done by adjusting the engine. The replacement strut could have been mounted out of alignment.

[rms95835]

Update: Had the old cutlass bearing replaced with one that was machined from UHMW plastic. Was the only option available in Samana, DR. Have since put 64 hours on this bearing and it seems to be working OK. Shaft clearance has remained consistent and as this is roughly equal to the number of hours that was put on the original bearing, I'm leaning towards the cause of failure being lack of use for 9 months, and a build up of barnacles or something that tore up the original bearing. That said, I now need to haul the boat to have the Volvo Penta dripless shaft seal replaced, and while out, thought it would be prudent to replace the plastic bearing with an original rubber style cutlass bearing . Dimensions on the original cutlass bearing are: 30mm ID x 44mm OD x 126mm L. I have had no luck finding a replacement online. The original is a blue non-metalic shell with rubber ID. Any help would be appreciated.

[Suijin]

Originally Posted by rms95835

Update: Had the old cutlass bearing replaced with one that was machined from UHMW plastic. Was the only option available in Samana, DR. Have since put 64 hours on this bearing and it seems to be working OK. Shaft clearance has remained consistent and as this is roughly equal to the number of hours that was put on the original bearing, I'm leaning towards the cause of failure being lack of use for 9 months, and a build up of barnacles or something that tore up the original bearing. That said, I now need to haul the boat to have the Volvo Penta dripless shaft seal replaced, and while out, thought it would be prudent to replace the plastic bearing with an original rubber style cutlass bearing . Dimensions on the original cutlass bearing are: 30mm ID x 44mm OD x 126mm L. I have had no luck finding a replacement online. The original is a blue non-metalic shell with rubber ID. Any help would be appreciated.

https://www.deepblueyachtsupply.com/...305700-bearing

30mm x 45mm. Cutlass bearings are compression fit. Put the bearing in the freezer for 24 hours before you install it, ideally with a Strut-Pro or similar tool.

It doesn't really matter that it's 6mm short. If you find one that's longer than 126mm just cut it down.

[boatbod]

I'd be real wary of a UHMW cutlass. Although it is slippery and a reasonable low speed material, it does absorb moisture and swell. My concern would be for lack of cooling and then having it melt underway. Ever seen monofilament fishing line after it wrapped around a cutlass?

[minaret]

No such thing as a "cutlass" bearing! It's a cutless bearing, as in it cuts less into your shaft. Just a personal pet peeve, sorry, the language police are gone now, carry on as usual...

[dennismckim]

Originally Posted by minaret

No such thing as a "cutlass" bearing! It's a cutless bearing, as in it cuts less into your shaft. Just a personal pet peeve, sorry, the language police are gone now, carry on as usual...

Should it not be "Cutless" with a capital C? It was, after all, a trademarked name held by Duramax Marine. As I understand it, it was then genericized to refer to all such bearings, in the same way that "Kleenex" and "Xerox machine" came to be commonly used in the US for all facial tissues and photocopiers.
Language evolves...