Using over-length cutlass bearing

[tburke]

A 25 yr old 26' Duffy has a 1 1/2" bronze shaft and a vented shaft cutlass bearing. It needs replacing. The surveyor noted the bearing to prop distance of 3 1/2" was longer than recommended (over 2 diameters I think he said). If I don't wish to cut down the shaft and re-key, is it sensible to press in a longer bronze sleeved cutlass and have it stick out say 3/4"? Would that effectively move the center of support aft 3/4"? If doubtful, any harm in doing?

No sign spurs and no wear marks to note the shaft had ever been more forward than now. But it had been re-powered with an identical TAMD31, though it was now the P version not the A, and as the forward clearance of the SW pump and deck cutout is only 1/2", maybe they had to move the whole engine aft to fit the opening??

Thanks for comments.

 

[bestfish]

If its been like that for 25 years, sounds like a direct replacement will work fine.

 

[tburke]

Sorry, "direct replacement" shaft?

 

[bestfish]

Sorry, "direct replacement" shaft?

The cutless.

 

[Brooksie]

I find no fault with your idea and I don't think you need a special longer cutlass (nor will you find one). I have always left my cutlass stick out of the housing 1/2-5/8" for years not so much for the support but for something to get hold of when removing it.

 

[chortle]

A 25 yr old 26' Duffy has a 1 1/2" bronze shaft and a vented shaft cutlass bearing. It needs replacing. The surveyor noted the bearing to prop distance of 3 1/2" was longer than recommended (over 2 diameters I think he said). If I don't wish to cut down the shaft and re-key, is it sensible to press in a longer bronze sleeved cutlass and have it stick out say 3/4"? Would that effectively move the center of support aft 3/4"? If doubtful, any harm in doing?

No sign spurs and no wear marks to note the shaft had ever been more forward than now. But it had been re-powered with an identical TAMD31, though it was now the P version not the A, and as the forward clearance of the SW pump and deck cutout is only 1/2", maybe they had to move the whole engine aft to fit the opening??

Thanks for comments.

Likely okay as is if it has worked for so long as arranged but knowing how long it has been arranged like this would be good to know. Is this a new boat to you? Any idea how many hours on the bearing? Any photos of the bearing and engine/shaft arrangements? Distance from the transmission output flange to the next support? Any idea how long it has been since the engine was repowered? If you can answer most or all of these questions it might help to understand whether or not it is worth making some changes.

 

[tburke]

Thanks for comments. To answer some questions;

The boat is new to me. Repowered 7 years ago. Likely same shaft as re-powered with same model Volvo (150hp). The cutlass is original and the surveyor remarked it was dry-rotted. Boat hours 1500, new engine 500. Output coupling to stuffing box is 24". Stuffing box to aft end of cutlass is 59". Aft cutlass to fwd of prop hub 4 3/4".

Photo of cutlass housing attached.

Thanks

 

[chortle]

Thanks for comments. To answer some questions;

The boat is new to me. Repowered 7 years ago. Likely same shaft as re-powered with same model Volvo (150hp). The cutlass is original and the surveyor remarked it was dry-rotted. Boat hours 1500, new engine 500. Output coupling to stuffing box is 24". Stuffing box to aft end of cutlass is 59". Aft cutlass to fwd of prop hub 4 3/4".

Photo of cutlass housing attached.

Thanks

Did not see the photo but the description supports my thought that what you have is fine. Pay special attention each year to the cutless for wear, after you haul out see if you can you wiggle the prop around by grabbing the prop and giving it a good wiggle. If you do this after the new bearing is installed it will give you a good baseline to compare it to at the end of the season. Also, pay attention to any excessive vibration that you might feel while underway at or near full speed while maneuvering, do some figure 8's while at speed to see if the prop is whipping or making noise or vibration. Try too imagine if this feels like the prop is trying to bend the shaft because it is sticking out too far. If you are not sure what these "seat of the pants" noises or vibrations are like then find a mechanic or friend who can help interpret this. Your surveyor may also be of some help with this.

 

[tburke]

Thanks. Never sent a photo before here. Will try again now.

 

[traditions]

One of the bad things that can happen when the cutlass sticks out past the housing is when you get rope in the wheel it can bend the exposed cutlass in and cut down on the flow of water,Seen it many times with boats with tubes that it is left long for removal. You may not be around a lot of rope and it may never happen to you.I don't think 3/4 of an inch would make a lot of difference in support .If it hasn't bothered so far I don't think it ever will.Just because some surveyor says he doesn't like it. I agree it looks a little long,but it doesn't seem to be a problem.You could always remove the housing all together and glass a short piece of tube in its place that is machined to hold the bearing.I did this on my old RP to get better water flow.The easiest and cheapest way to solve this problem is to remove the shaft and cut it off and cut a new keyway for the coupling.

 

[chortle]

Thanks for comments. To answer some questions;

The boat is new to me. Repowered 7 years ago. Likely same shaft as re-powered with same model Volvo (150hp). The cutlass is original and the surveyor remarked it was dry-rotted. Boat hours 1500, new engine 500. Output coupling to stuffing box is 24". Stuffing box to aft end of cutlass is 59". Aft cutlass to fwd of prop hub 4 3/4".

Photo of cutlass housing attached.

Thanks

Good photo, just run it and monitor it.

 

[captainlarry84]

Thanks. Never sent a photo before here. Will try again now.

You have way too much unsupported shafting after the cutlass bear. Moving the bearing back so it is not supported by the bearing housing is not an option. I would re-shaft the boat with SS A-22 Shafting & make it about 2" shorter. If you really want to keep the bronze shafting which is only as strong as about SS A-19 the your only option is to cut the shafting at the coupler as you will not have enough shafting material to cut the tapered end, which is the end that gets all the stress. Once done your shafting at the stern bearing should look like this, with just enough shafting exposed for a donut zinc.

 

[Keelboater]

Guys, I have to go with Captain L on this one. Usually about 1 - 1 1/2 times the shaft diameter between the bearing and the prop hub is the norm. Maybe a bit more if you have a line cutter. It may be time to think about a shaft modification if you want it done the right way. :roll:

The more exposed shaft there is, the greater the tendancy for side loading of the shaft to occur.

When side loading of the shaft occurs, it can deflect the shaft where the prop is located.

When you get shaft deflection where the prop is located, it creates vibration.

When you get vibration, that's all you can think about so you can't sleep at night.

When you can't sleep at night, you decide to shop at a convenience store at 3 AM.

When you shop at a convenience store at 3 AM, it gets robbed and you mistakenly get thrown in jail wearing your fuzzy rabbit slippers.

Don't get thrown in jail wearing your fuzzy rabbit slippers. :shock:

 

[Toro]

Your surveyor is right, that looks diriculous. That arrangement is not long for this world.

I suppose you could have a prop shop cut it down, but be prepared to find pitting around the shaft log area and elsewhere when you have the shaft on the bench. If that is the case, definitely replace the shaft with an Aquamet , preferably 22, and have them cut it to a double taper. If you go to that length just replace the coupling...

 

[Bill]

Question, may or may not be dumb but I just dont know..Im putting my boat backtogether keeping the wet keel and the stern bearing..Now my old stern bearing has the cutless bearing about 2/3 of the way and then nothing for 2 inches on the propeller end of the bearing.. I would assume that the cutless is supposed to go all the way through it? It makes no sense to me.. there was packing burnt on to the shaft which was in this void which makes no sense.. I am assuming that the wrong cutlass was installed ( to short) and so downeast dickerers put packing in there? any thoughts? never owned a boat with a shaft so this is new to me. thanks

 

[Numasahake]

If it was mine, I'd put a new packing in that extends to the end of the housing, and shorten the shaft, re-key. Yes AQ22 shaft the correct length would be the best option, but lets face it, the little Volvo 31 is not exactly a torque monster. Another benefit by shortening the shaft, you should see cleaner water to the prop. I've seen in my Northern Bays, for every inch that I could bring the prop closer to the dead wood, I picked up 1 mph!

 

[Brooksie]

Question, may or may not be dumb but I just dont know..Im putting my boat backtogether keeping the wet keel and the stern bearing..Now my old stern bearing has the cutless bearing about 2/3 of the way and then nothing for 2 inches on the propeller end of the bearing.. I would assume that the cutless is supposed to go all the way through it? It makes no sense to me.. there was packing burnt on to the shaft which was in this void which makes no sense.. I am assuming that the wrong cutlass was installed ( to short) and so downeast dickerers put packing in there? any thoughts? never owned a boat with a shaft so this is new to me. thanks

The rubber part of your cutlass has debonded (word?) from the bronze part and slid. Install a new cutlass and keep it flush with the outer end. The extra space isn't for packing, it is: inside= in case you need to thread it for a certain type installation, Outside= so it fits closely into the deadwood so you are not relying just on the bolts to locate it exactly.

 

[Toolate]

I've seen in my Northern Bays, for every inch that I could bring the prop closer to the dead wood, I picked up 1 mph!

Really!?! Should we all be pushing our props tight and running those bullet zincs? Think I might have an extra 1/2" in there....

 

[chortle]

I agree with Brooksie, the rubber element has lost it's joy with the bronze sleeve, it needs to be replaced. Any packing shoved in there seems like a work-around to keep running until it could be replaced.