Max Prop is AWOL

[TradewindSailor]

I bought my Catana with 2 Maxprops fitted in 2008. I've never needed to remove the hubs.

Anyway ..... I had just cleaned them a day before one disappeared leaving the Yanmar SD 20 shaft clean. The fixing bolt has completely gone with the rest of it. All the Maxprop dealer has to say is that the bolt must have come loose.

When I get hauled out in a few weeks I am going to remove the other hub bolt, clean it and the thread up properly and use a waterproof Locktite as I suppose would have been originally required.

I can't afford to loose another 15" Maxprop ..... so I'm going to get a folding prop. If it performs well I may make it a pair and there may be a Maxprop available for a new owner!!

 

[Talulah]

The Maxprop has two pins that go in either side of the nut. This is to prevent the nut from coming undone. I wonder if the pins were left out when the prop was reassembled.
I use to have Maxprop but have switched to J Prop. (An improvement on the Maxprop design.)

 

[sailorman]

Thanks for the heads-up. on searching i found this
http://www.ybw.com/forums/showthread.php?14229-J-Prop-versus-Max-Prop

 

[macd]

The Maxprop has two pins that go in either side of the nut. This is to prevent the nut from coming undone.

Mine's like that, but the drawing in the handbook clearly shows a single pin radially through the nut: quite a different arrangement. Whether earlier or later, I've no idea.

 

[TradewindSailor]

I'll have to look at the other Maxprop when I take it off, but I think the hub I'd fitted on with a nut and a bolt is passed through the shaft and torqued up to lock both the nut and the bolt. This would make sense with the thread in the centre of the shaft.

I am aware that some sd20's had the ends of the shafts drilled for a spit pin ..... Presumably holding on a castle nut ..... but these shafts have been known to break at the pin hole.

I know the two pin locking mechanism of the Maxprops ...... in that I've seen the drawings. I'll let you know what I find when I take the remaining one off ......

 

[TradewindSailor]

Update: The Maxprop is held onto the SD20 sail drive with a conventionally threaded nut with a conventionally threaded bolt through the centre of it and the shaft. This is rather unusual as I would have thought the threads should oppose each other to form a proper lock.

However ..... I can confirm that NO Locktite thread locking fluid was used on the remaining prop hub AND although the locking bolt was tight the nut was less than finger tight.

Moral ..... it is worth checking that the propeller is installed properly ....

 

[J Neeves]

I find the method of securement less than satisfactory - but is there not (or should there not be) a tab washer between nut and bolt? In any event we have used Loctite on both nut and bolt and (edit, we have also used a) tab washer.

I know there is a hole in the end of the shaft - but have not seen any instructions where it is actually utilised.

Jonathan

 

[Talulah]

Last weekend I removed an older version of a Maxprop.
The nut on the end was not a proper hexagonal nut but was rounded with two flats. i.e. You could get an adjustable on it but not a socket.
The nut was secured with a pin that went in one side and out the other passing through a hole in the prop shaft.
If your nut is hexagonal shaped as per a proper nut and with no hole passing through it then I suspect it is not the original MaxProp nut.

 

[macd]

Talulah: that sounds the same as the drawing I mentioned in post #4. Mine (which I think is later) is quite different: the nut is a hex, but with semi-circular scallops in each flat, on an axis parallel to the shaft. A pair of steel pins are inserted in these which engage in blind holes in the forward part of the hub. It's fiddly and not altogether reassuring.

 

[savageseadog]

SD20 saildrives have two different designs depending on age. The older design the shaft had a hole through which a split pin went together with a castellated nut and locking screw. The newer saildrives don't have the hole and propellers rely on Loctite, tabbed washers and locking screw/bolt. The locking screw and larger nut are both Right Hand thread which isn't really correct. The problem with the old design was the hole weakened the shaft and it could break if over tightened.

 

[TradewindSailor]

I don't understand how a tabbed washer would work as there is no keyway or flat on the shaft to keep it from rotating with the nut.

The nut also has a rounded front portion that would tend to prevent the tab on the washer working .....

 

[J Neeves]

It does not work.

Big nut and the small bolt are meant to be torqued, but that appears insufficient. There are no instructions to use Loctite, though instructions for other parts of the prop do use Lictite (so its not as if they assumed you would use). We must have a transitional SD as it has a hole in the shaft, the big nut (we bought a big socket to move it as it is well recessed) and a bolt that is the final component. I did think of drilling the nut and bolt but it was too fiddly to attempt at a boat yard - so used Loctite. Last time we disassembled, about 6 weeks ago the nut and bolt were lose (and we have 2 SDs).

The method of assembly sounds good, lots of torquing a tab washer one nut and one bolt - the reality is that it ensures propellor sales are maintained.

I hate to mention anchors - but I am constantly amazed at the number of anchor makers and prop makers who exhibit at boat shows. The numbers of new vessels does not seem to support such a vibrant couple of industries (especially as new vessels use the cheapest offerings available). I know some people upgrade from the minimalist offerings of the new yacht and some anchors and props are damaged (or over 20 years wear out) but I suspect many more props and anchors are lost than are ever reported. And neither of them are cheap.

Jonathan

 

[TradewindSailor]

Just an update: there is another catamaran in the yard that has just pulled out missing an 18" 3-blade volvo feathering prop. off their SD 20!!

Seems like a money spinner .... I must get an underwater camera and metal detector ....��

 

[J Neeves]

Just an update: there is another catamaran in the yard that has just pulled out missing an 18" 3-blade volvo feathering prop. off their SD 20!!

Seems like a money spinner .... I must get an underwater camera and metal detector ....��

Ouch!

 

[mobeydick]

Just an update: there is another catamaran in the yard that has just pulled out missing an 18" 3-blade volvo feathering prop. off their SD 20!!

Seems like a money spinner .... I must get an underwater camera and metal detector ....��

You might see a diver with a spanner and a heavy bag? Considerate though, as he is only taking the 'spare' from catamarans...

MD