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Old 25-06-2012, 04:49   #31
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Re: Smoke from shaft and cutless bearing!

Quote:
Originally Posted by sdowney717 View Post
measure then order some vesconite bushes.
They are self lubricating, dont swell in water
Sorry to disagree but...this is from their own data sheets.

Vesconite bearings do swell in water (0.50%) and this is an important part of the running clearance.Running clearance will need to allow for thermal as well as moisture expansion. 0.05 + (0.02 x wall)

For a 25.40 shaft in a 40.00mm carrier (7.30mm wall) vesconite is 0.196mm clearance.

Maritex is 0.13 as it has lower moisture and thermal expansion, it has also shown very low wear rates is self lubricating but also non melting or softening.
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Old 25-06-2012, 04:56   #32
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Re: Smoke from Shaft and Cutlass Bearing !

i can reccomend vesconite,having used it on a previous boat that we circumnavigated on,we used 0.2mm clearance,and 12 years later they were still in service.
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Old 25-06-2012, 05:22   #33
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Re: Smoke from Shaft and Cutlass Bearing !

The cutlass bearing is designed to run under water and to be cooled and lubricated by water. If the cutlass bearing is hot and smoking the first place to look is why it is not getting the water it needs.

The smoking and burning rubber smell is a big clue that it is not getting even a little water. Don't waste your time on the alignment and size issues until you get it wet!
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Old 25-06-2012, 05:42   #34
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Re: Smoke from Shaft and Cutlass Bearing !

[QUOTE=4HMainer;977541]
Question.
How long is the stern tube?
Is there any water feed to the tube from the engine?

The cutless bearing is is 4" long. Unsure of the tube length, but close to that.

No water feed from the engine. Just a packless water seal.

Thanks for your help.
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Old 25-06-2012, 06:00   #35
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Re: Smoke from Shaft and Cutlass Bearing !

So the bearing is just behind the gland, maybe a stupid question but how deep is this bearing under the water? can it suck air down and cavitate (some cats do this)

Is tube horizontal or angled down, if it was flat and the water channels were blocked with grease with a slightly leaky gland it could dry out.

For smoke it must be completely dry at the front end as comment above.

This part should always be full of water and have some connection to open water or a water feed to allow the water to conduct the heat away. Misalignment will wear the bearing but not cause dry running so focus on how the water can get to the bearing under all conditions.
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Old 25-06-2012, 08:54   #36
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Re: Smoke from Shaft and Cutlass Bearing !

Yeah, the "smoke" thing has got me wondering too. How is smoke getting past the dripless bearing? A hot shaft could generate steam, but not the odor mentioned.

The recent versions of the dripless bearing come with a "vent" in the "carbon" part that is installed in the rubber expansion tubing which is attached to the shaft log. The vent allows the trapped air to escape.

Evidently too many dripless bearings were overheating due to trapped air causing insufficient water lubrication. Only the older versions of the dripless bearing did not have the vent and needed to be opened or "burped" especially when it is suspected that air has entered the shaft log/cutlass bearing.

Engine mounts are easily available - but you need to be careful to get an engine mount "style" that matches the vibration and thrust factors of the engine. "Soft" engine mounts absorb a lot of vibration but also allow the engine to move too much fore and aft when the propeller is engaged. "Hard" engine mounts greatly reduce the fore and aft movement of the engine but also transmit the vibrations.

I have seen worn engine mounts that allow the engine/transmission to move too far forward or aft which results in a changing angle of the propeller shaft through the shaft log. With old mounts, I fix a pointer or screwdriver to a hull part and have the pointy end pointed at the aft edge of the transmission flange assembly. Then I operate the engine in forward and observe how far the engine moves - likewise, in reverse.

If the movement is excessive then you (with a slanted propeller shaft relative to the boat) might be changing the relationship of the propeller shaft and the cutlass bearing enough to cause excessive wear or binding. Additionally, with excessive fore and aft movement, the propeller itself could move and come into contact with the hull or shaft log or anything behind like the rudder.

Seems that as things get old, be they boats or folks, things get too loose and need some tightening . . .
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Old 31-07-2012, 16:40   #37
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Re: Smoke from Shaft and Cutlass Bearing !

Update, Update! Thank you again for all your thoughts and ideas on our shaft cutless bearing questions. PWC is doing what it should and the bearing is not a problem as suspected. On to what may be the problem. As a reminder, we have a later 60's Petter diesel (AB1W), 1 cylinder, 6 HP. Now after being the hole and getting some advice from a local person who has one of these little 1 cylinder jewels (for a generator), we have some new info. After finding water in the diesel fuel and taking a long time to new filters and get all that fixed, we were on again to the "mystery smoke" issue. Starting the engine at the dock and it purrs like a kitten until you put it in gear running the engine gently. Goes forward for 4-7 minutes just fine, then starts to slow down and will shut down unless you put it back in neutral quickly then it purrs again just fine. As the engine is "slowing/pulling down is when you notice the "smoke" coming up from the engine hole. First let me say, this engine is in a tiny, tiny space and my wife volunteered to crawl down into the hole to check out the "smoke" source. A flashlight revealed the "smoke" is actually a hole in the water cooled copper wrapped exhaust pipe coming from the engine. 1/4" hole hard to see as it is partly under the copper cooling tubes. Flashlight held there makes the exhaust show up when the engine is running. SO very embarrassed that we thought it was smoke from the cutless bearing. BUT, the exhaust really comes out more as the engine starts to choke down after being in gear a few minutes. We have no mechanics around here that know anything about diesels, but the good ole boy consensus is that it may be something going on in the "drive train" (same as transmission?) We are going to change the engine oil and filter (not been done in a LONG time but likely this engine has no more than 150 hours total in it's 40 year life span). Might this old oil be the problem? DOes the engine oil lubricate the transmission/drive train? Does this sound like a transmission issue? when you put it in reverse, it will slow down quicker then stop. The stopping process sound is very short, but sounds rather like metal rubbing. But again, when you quickly put it back in neutral, it runs like a dream. Our old manual give recommendations for "stern gear grease". Also, manual does not tell you where to put said grease.
Now, any new ideas out there???? Thanks again for any help you can provide!!
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Old 01-08-2012, 07:01   #38
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Re: Smoke from Shaft and Cutlass Bearing !

Been a while since your last update and I don't recall all the details and suggestions from previous posts (and am too busy/lazy to go back and read them all) so may be repetitive here but.

1. In this case drive train would be everything after the engine all the way to the propellor.

2. After you run the engine in gear for a while and it stops but still runs in neutral:

a. can you turn the prop shaft by hand? If in appropriate location can you swim down to the prop and turn it by hand (make sure engine is off for safety)?

b. Can you reach the stuffing box? Is it hot to the touch?

c. Same question for the cutlass bearing.

d. with the engine in neutral will it freely rev up to higher rpms?

My thought process here is after running the engine in gear it stops so could be the stuffing box or cutlass bearing heating up and binding. Other possibility you have some sort of restriction in the fuel line that slowly stops the fuel flow to the engine causing it to bog down.
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Old 01-08-2012, 07:26   #39
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Re: Smoke from Shaft and Cutlass Bearing !

Thanks Skipmac for suggesting a few more things to try. We have a packless water seal and it has a mist of water coming out when prop is turning. We had earlier thought smoke was coming from there, but actually, the "smoke" was exhaust from a 1/4" hole in the exhaust pipe. Tried to patch it with "stove seal" but did not get the hole plugged all the way because the copper cooling coils wrapped around the exhaust prevented us from getting the total hole closed.
I will try to hand turn the prop shaft after the engine pulls down. A thought: if you try to hand turn it and it is very hard to do, how would you know if the stiffness if coming from the cutless area or if the transmission is locked up? We put a new cutless bearing in this spring when boat bottom was painted. Old was was not that old and not worn much and worn evenly. When engine pulls down completely, there is a 2 second "metal on metal" sound --- we think. CUtless bearing would not make that sound. Right? When we put new oil in the engine (has not been changed in years so thought we would try that in case oil was not getting everywhere it should), does that oil run into the transmission area? Another question: Manual says to use a certain kind of grease in the "stern gear". Have no clue where that is. Not mentioned in manual. Might this be the problem? So frustrating with no mechanic around.
Thanks for any help.
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Old 01-08-2012, 07:51   #40
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Re: Smoke from Shaft and Cutlass Bearing !

As far as I know, transmissions have their own oil or hydraulic fluid and will be separate from the engine. There might be some exception to this but not on any of the boats I have owned.

You need to look closely at the transmission for a fitting or maybe even a large bolt head on top of the transmission case that could connect to a dip stick showing fluid levels in the transmission. The metalic noise and the lock up after a few minutes could very well be lack of oil in the transmission.
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Old 01-08-2012, 07:54   #41
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Re: Smoke from Shaft and Cutlass Bearing !

Is it possible that the exhaust Co2 is filling the engine room, choking off the o2 supply to the motor? I have seen this before with exhaust leaks on outboard motors, where the space inside the cowling fills with exhaust, and makes the motor run rough. --Chris
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Old 01-08-2012, 07:58   #42
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Re: Smoke from Shaft and Cutlass Bearing !

For what ever reason you have either NO water or too little water behind your seal.. FYI: NEVER brass ALWAYS Bronze... Apples and oranges with the same color!
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Old 01-08-2012, 08:13   #43
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Re: Smoke from Shaft and Cutlass Bearing !

We wondered if the exhaust in the engine area might effect the engine performance, but how could that cause the metalic sound when it cuts all the way off. Engine does run smoothly when in neutral and when in gear - for a few minutes. Might try to funnel the exhaust out through the top engine access opening by using alum foil to see if that makes any difference (have to be creative) Also, will try to see if we can find any entry into the transmission area for fluid, oil, grease....... will be Friday or weekend before can get there again. Any other things to check, please do so in simple terms (novices here) Thanks again....
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Old 01-08-2012, 08:15   #44
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Re: Smoke from Shaft and Cutlass Bearing !

Also, packless water seal is spewing water mist when the shaft turns. We burped and know it has water in it. Bronze shaft also. Thanks
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Old 01-08-2012, 10:46   #45
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Re: Smoke from Shaft and Cutlass Bearing !

I think it is possible you have two separate problems. Perhaps after repairing the exhaust leak, you will have a better set of data points?
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