Cutlass Bearing Failure

I took my Defever 49 CPMY out of water to get painted and some other minor work done. Upon return 3 out of the 6 cutlass bearings failed where the inner material had seperated from the cutlass and moved down the shaft so my question is how long are the good for and what would cause them to fail I had all 6 replaced September 2015 at Cable Marine in Fort Lauderdale FL

All on the same shaft?

Ted

Cutless bearings should be good for decades provided shaft alignment is with tolerance. Cable marine either used the wrong OD, failed to install the set screws, installed set screws with the wrong point, or didn't bother to check shaft runout.

You have no recourse as any warranty would be time limited and you have been using the boat for 3 years. Have a new yard repair the problem.

Cutlass bearing use to be a very rare failure. Seems more common in the last few years. What kind of use (engine hours) have you done in the last three years? Any prolonged periods without use? Have you hauled in the last three years or had the running gear cleaned?

Ted

SoWhat said:

Cutless bearings should be good for decades provided shaft alignment is with tolerance. Cable marine either used the wrong OD, failed to install the set screws, installed set screws with the wrong point, or didn't bother to check shaft runout.

You have no recourse as any warranty would be time limited and you have been using the boat for 3 years. Have a new yard repair the problem.

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I think you're misreading the OP. The rubber separated from the bronze in the cutlass bearing.

Ted

The same thing happened to us once. We wrapped a line around the shaft/strut that stopped the engine. The side pull, as everything got wound, separated the rubber (what ever it’s made of) from the bronze.

I’d check the shafts to see how straight they are and the alignment of the struts/shafts when everything is put together.

Did you hit anything or did the boat sit for an extended period? You could have had growth in the bearing/shaft that once you started it, the friction of the shaft/bearing caused it to break loose.

O C Diver said:

I think you're misreading the OP. The rubber separated from the bronze in the cutlass bearing.

Ted

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You're correct. I misread it. If the 3 are one shaft then there must have been a lot of torque on the shaft. Or the parts were made in China.

Guessing a bad batch. Give the yard a call. Maybe they had others.

Looks like bad adhesion between the rubber core and bronze sleeve. Go back with a name brand bearing.

Cable Marine has been around for years and has a good reputation. I would ask them what could have caused all these failures in such a short period of time. Could be a bad batch from the manufacture. Mine usually last for years.

I recently replaced the bearing in my stern tube. It did not have a bronze casing, but something that looked more plastic, or fiberglass. It looked like what you are showing in the pics. The new one was identical. I had to drill holes and install set screws to keep it in place.

Is it possible these have fiberglass outlets and set screws were not placed?

Gordon

I grew up on a boatyard. Here is what I think happened. We regularly put bronze cutlass bearings in dry ice so they would shrink just enough to slide them in without to much resistance. Unfortunately the rubber formula must have changed and we started getting failures such as yours... rubber separating from the bronze.

Thanks for all the help. There are 3 on each shaft so two off of one and one off the other. The boat has not been out since cable had it out I do not think about Cable Marine in a pleasant way after about a year The port shaft came out of coupler the set screws were not wired or lock tighten now it might have been a bad batch and they are human so that probably excuses the coupler work but if I dont say something it becomes a secret

When they pull the bronze parts out, it would be interesting to see if there is a manufacturer's name or mark on the bearing. The 3 I have replaced were all the same brand and are still in service. Wondering if there are now Chinese junk bearings infiltrating the market.

Ted

dry ice bearings?

Garywbryan said:

I grew up on a boatyard. Here is what I think happened. We regularly put bronze cutlass bearings in dry ice so they would shrink just enough to slide them in without to much resistance. Unfortunately the rubber formula must have changed and we started getting failures such as yours... rubber separating from the bronze.

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I've heard of icing bearings on interference fit but using dry ice? Everything gets brittle with that. I'd check with the bearing MFG to see if the "rubber" part can tolerate -109 degrees F... Brrr!

Even if a frozen cutless bearing can stand the press operation, make sure the rubber has thawed out before you start putting the shaft back...

Excessive heat caused by misalignment or marine growth blocking the valleys are common reasons for the rubber to separate. Looks like there was a lot of marine growth on unpainted items.

Assuming the correct size was installed which is easy enough to check, I am assuming the dumb (bad word) installers didn't know what the (another bad word) they were doing.

Years ago, The Maritime Reporter reviewd a wooden cutlass bearing, stating:

When C.S. Inter Marine’s management decided to change the engine on one of its small tugs with a new Cummins KTA19 M3 rated 640 HP at 1800 RPM, Khun Patum, Shipyard Manager, pulled the boat up on the bank at the company shipyard in the ancient Thai capital of Ayuthya some 50 miles up from the Gulf of Thailand. The old engine came out easily through purpose-built skylight. At the same time Khun Patum had the 7:1 gear pulled along with the shaft and four-blade 75x16-inch propeller for service and inspection.

With the shaft sitting out on a bench, he explained to a visitor the cost to benefit advantages of the Tamarind wood [cutlass] bearings he uses in the company tugs. “A vinyl bearing costs about 90,000 baht ($2,500 US) while I can have these made for only 3,000 baht ($75.00 US)”

In America, lignum vitae wood was used for many years in shaft bearings. Writing in Power Transmission Design Magazine, Managing Editor Tom Hughes reported, “…early users of wood bearings (bearings with no impregnation of additional lubricant) were ship builders and woodworking shops making underwater shaft bearings for tugs and freighters. The natural resins inhibited water absorption and served as a base for a water film between bearing and shaft… Wood bearings operate well in abrasive environments. Gritty particles that manage to reach the bearing surface embed harmlessly in it.”

Demonstrating the good and minimal wear of the year-old bearing, Khun Patum explains that he carefully selects a tamarind log from a tree that is at least 20-years-old. The last one he purchased for 2,500 baht. After aging one week in the shade, he had eight (four sets of two) bearings turned at a local lumberyard. The two-foot long tail bearing for this shaft has an 8-inch interior diameter with 5/8-inch walls while the forward bearing keeps the same diameter but is 16 inches long. “I normally inspect the bearings every three years but they will last indefinitely if we keep a good water flow over them to lubricate and remove the river’s sand,” he explained.

In doing a cost benefit analysis it may be that new machinery is the best investment, but in others it may be that staying with the tried and true is the best course.