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Old 11-19-2013, 10:03 AM   #1
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Running Gear and Cutlass Bearing

My major winter project this year is to tune up the running gear. We spend the summer with a warped shaft and it is time to change it. We plan to completely replace it and get the prop tuned (that's a discussion for another thread).

I have two general questions---

Is there a cutlass bearing or is it just a shaft bearing? Moreover, where is it and what do I need to know about changing it?

Should I spec the shaft a little bit longer to leave room for a shaft zinc? Would that replace the carbon brush or will I still need that?

Below is a picture of the current exit hardware of the shaft. Any advice would be awesome! (and yes, I know that was four questions and not 2)

Thanks team.

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Old 11-19-2013, 11:03 AM   #2
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Hi Tom,
Looks like you've got a nice set screw on your housing. I wish I had as much.

The "Cutlass" bearing is the aft shaft bearing. GF Goodrich sold rubber shaft bearings on the 50s called "Cutlass" bearings. My guess is that the rubber does not wear like harder bearing materials that tend to get cut down by sand or other hard materials that may come in contact w the shaft. Common bearing practice is to have a soft material like brass for a bearing to a harder part like steel. The cutlass bearing seems to be the extreme end of the soft bearing hard part practice. The "flutes" pass water through the cutlass bearing for good distribution of that lubricant.

Here are two pics that show the type of zinc I've been using. Thev'e been known to fall off but I've had good luck w mine for some time. You can see that I was long overdue for a new zinc in the second pic.
I prefer to keep the prop hub to stern bearing distance (gap) small. Just plenty large enough for good water flow out of the flutes of the stern (cutlass) bearing for good lubrication. I have a force fed water feed to my stern tube so I could get by w a bit less clearance but an inch or so should be fine. I think for support and vibration potential the gap should be minimized and that's basically why I use this common system. You can see the allan head socket screw that holds the zinc in place. It should be installed w thread locker. I've used both red and blue. And w the zinc eroded away the specialized nut can be clearly seen. The third pic shows my very small set screw. It is threaded into FG and every time I use it I fear I'm going to strip out the FG threads.

Removing the stern (cutlass) bearing can be troublesome. If the bearing was installed w a too tight fit and pounded in hard you will may need to remove the shaft and drive it out w a drift or ram from the other end. I have removed them by drilling a hole in the brass of the stern bearing and pulling it out w a screw driven into the hole. On could even use multiple screws and tap the holes per the screw thread.
But if the bearing was installed correctly it shouldn't be too difficult to get it out. Just back out the set screw and stick something sideways into the rubber and drag it out.
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Old 11-19-2013, 11:17 AM   #3
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Google... Who knew? ;-)

Found this little tid bit- Mainship 34 New Running Gear, Prop, Shaft, Dripless Stuffing Box
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Old 11-19-2013, 11:21 AM   #4
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The carbon brush is the answer...but a shaft zinc is all many have...I would go a little longer shaft or get justa bug enough spacer to put a shaft zinc on...but I wouldn't sweat it if it's a big deal...if your prop hasn't been seeing galvanic corrosion you are in good shape with the brush.

The set screw(s) is for the cutlass bearing...you'll need to spec it with shaft size, outer bearing diameter and overall length. As long as your shaft is going to be out, getting the old cutlass out is easy as you can cut it out with a hacksaw blade or reciprocating saw (be careful of the carrier but a nick or two doesn't matter)...the new one goes in with a wood block and a sledge but I prefer to clean everything up to the point where it goes in without any pounding...just convincing.

Cheapo rubber and brass cutlass bearings last for years and thousands of miles (hundreds of hours) if you aren't in a lot of abrasive water. Someone on here used to advocate some miracle ones from Michigan or the Mid-West...not a bad idea but unless you cruise all year long for years...probably overkill.

If you haven't ever had your shaft out and have a solid coupling...if it doen't come off easy...I cut mine off in minutes with a cutting wheel in a 4" grinder. Always cut down and into the shaft key...they are lots cheaper than new shafts
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Old 11-19-2013, 04:54 PM   #5
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After a bit of snooping, it doesn't look too hard to do. This will be my first shaft removal, so I expect a few problems and a learning curve. I think that the only think I will get professional help with is replacing engine mounts and aligning the whole thing. Skinny Dippin's prop shaft isn't too long. I am guessing about six feet or less. New shaft is only about $700, plus prop job at about $250 ($400 if I re-pitch).

So should I do both? Zinc and brush?
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Old 11-19-2013, 05:07 PM   #6
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belt and suspenders...but not worth a cent more if the brush has been working fine.
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Old 11-19-2013, 05:19 PM   #7
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The bearing case should just unscrew.
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Old 11-19-2013, 09:54 PM   #8
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Ya'll do know those are actually Cutless bearings?
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Old 11-19-2013, 11:50 PM   #9
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What does the word "cutlass" mean Steve?
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Old 11-20-2013, 04:20 AM   #10
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Cutless® is a registered trademark of Duramax Marine® LLC.

A cutlass is a short heavy sword with a curved single-edged blade, once used as a weapon by sailors.

A Cutlass is also an Oldsmobile first built in 1954 and named after a a disaster of an airplane built by Vought.
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Old 11-20-2013, 09:00 AM   #11
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Also in the English speaking countries of the Caribbean you will hear a Machete called a Cutlass.
From the internet: "The word cutlass developed from a 17th-century English variation of coutelas, a 16th-century French word for a machete-like blade (the modern French for "knife", in general, is "couteau"; the word was often spelt "cuttoe" in 17th and 18th century English). The French word is itself a corruption of the Italian coltellaccio, or "large knife", derived ultimately from Latin cultellus meaning "small knife."[

The only reason I can think for a bearing to be named that is that, hopefully, doesn't score the shaft?
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Old 11-20-2013, 01:26 PM   #12
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Cutlass also is used quite a bit with the bearing...even in boating and DIY articles...not saying it's correct...as actual sellers of the product call it a "Cutless Bering"...but hard to keep straight when it used maybe more one way than the correct way...

My search turned up way more usages with the "a" than the "e"...but I know the correct spelling is with the "e"...
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