This issue took place over the past few years. I am puzzled. I had Kiwi prop for a few years when I, by chance, noticed the shaft wobbling/whipping only at 1600-2200 rpm approx. Any other rpm its fine. When I say wobble I mean it shakes the engine - not normal Luckily I don't use this rpm range much. In trying to fix the issue I had the boat pulled, removed and checked the bronze shaft for straightness, installed new cutless, engine mounts, and re-aligned engine. Done by yard. Still had same wobble after all this. $$$ #%& So I pulled Kiwi prop and put standard fixed prop back on. No wobble. Sent Kiwi back to be checked out & re-set. Put back on next season. Wobble is back. Next season I decide to pull PYI dripless stuffing box (which I really liked) and put old stuffing box back on. My thought was that the stuffing box would steady the prop shaft like a bearing which the PYI unit does not. No luck. That Kiwi will just wobble at that rpm. That's where I am at now. I just make it a point of staying out of that rpm range until my next move. What is my next move? I like a feathering prop but I think I am done with the Kiwi. Would a Max-prop give me the same issue? Hate to spend the money to find out. Would it do any good to replace the bronze shaft with a SS? Thanks.
Tough Prop issue
- Thread starter Pat T
- Start date
Who knows? I had a Kiwi prop with no issues, so I know it can work well. Motor and transmission mounts? I would be inclined to buy a fixed prop (cheaper simpler) and see if that fixes it.
Can't tell you right now how close hull is to Kiwi. The water is kind of cold here now for me to jump in and check w/o wet suit. However I think both props (Kiwi & fixed ) are similar in diameter.
John,
My old fixed prop does solve the problem. I still would like a feathering prop though.
A prop should be no farther from the cutlass bearing than 1.5 times the diameter of the shaft. I'm not familiar w/the Kiwi prop, but it could, as some other folding/feathering props do, put the prop much farther out on the shaft. A bronze shaft might allow a bit more movement in it than the equivalent SS shaft?
I'm not saying to replace the shaft, but just putting out ideas. Also, two questions. Did you remove the shaft and have it checked out by a proper machine shop? Any visual or in place check would still leave some room for doubt. Who checked out the Kiwi prop? Many of the feathering props need to go back to the factory for restoration, most prop shops can only service them.
As MaxProp if they'll take back their prop if it does the same thing. They now have a 4 blade which should stop a lot of vibration issues.
I'm not saying to replace the shaft, but just putting out ideas. Also, two questions. Did you remove the shaft and have it checked out by a proper machine shop? Any visual or in place check would still leave some room for doubt. Who checked out the Kiwi prop? Many of the feathering props need to go back to the factory for restoration, most prop shops can only service them.
As MaxProp if they'll take back their prop if it does the same thing. They now have a 4 blade which should stop a lot of vibration issues.
Thanks Capta. The yard did pick up on the prop being too far away from the cutlass bearing and did shorten it. It is a 1 in shaft and I am guessing there is about a 1 in space between the cutlass and the prop. However, it made no difference. When the yard pulled the shaft they sent it to a machine shop for check out. I did send the Kiwi prop back to the Kiwi rep. If I get a MaxProp or any other I will indeed inquire about their return policy.
I have a 3 blade flex O fold and it runs so smooth that when I was racing my crew could not get over how smooth
they run around $2000 and has been on my 2007 H-36 since 2007 and no wear and still is like new and no greasing
or adjusting needed and is so much better than my fixed prop and great sailing and reverse and it folds,easy simple.
Nick
they run around $2000 and has been on my 2007 H-36 since 2007 and no wear and still is like new and no greasing
or adjusting needed and is so much better than my fixed prop and great sailing and reverse and it folds,easy simple.
Nick
1) i second the flex o fold. have had one for 10 years now. smooth and faultless operation.it is a beautiful piece of machinery. the company is also very responsive to questions. 2) who checked the face out on your coupler? if that is out by several 1000ths of an inch it can be a factor in shaft wobble. did you ever check the tip clearance between the end of the kiwi and the underside of the hull, and is it the same clearance as the fixed prop? ? insufficient tip clearance can cause ghastly vibrations. if the prop is mounted on a longer shaft with more distance from the cut less bearing it may well gain more tip clearance -- moving the prop further down the shaft . cutting the shaft generally reduces tip clearance. i hope some one checked tip clearance before cutting off an inch of the shaft . doing that without knowing how that affects tip clearance is not a good idea. 3) get a ahold of dave gear's propeller book... which as soon as i lay my hands on my copy i will do...
I'm not an expert in folding props, but did you check the pitch in the blades? Maybe one's off a bit causing the vibration. I still have the OEM fixed 2 blade on my H376. I was getting vibration over 2500 rpm. Had my diver pull prop and sent to prop house. Yep... both blades were off 10-15%. It was the best $250 I ever spent.
Bob
Bob
The Kiwi prop is stupidly simple. The blades are plastic and free to flop around independently. Somehow the hydrodynamics of the situation force them against either the fixed reverse stop (when reversing) or the adjustable forward stop when going forward. There is no internal gearing and nothing would prevent each blade being set to a different pitch, (which might cause your problem). I dunno I can't imagine there isn't another Catalina 36 somewhere with this system. But for whatever reason it sure seems like it isn't working for you.
To answer some of the past replies: Run-out on face of coupler ? - Not sure if the yard checked this but if there is no wobble under 1600 rpm & above 2200 rpm with the Kiwi and no wobble with the fixed blade prop so I am guessing the run out is minimal. Tip clearance? Can't remember for sure but I am guessing I checked this during the original installation and it was ok. There are also other Catalina 36's out there with the Kiwi so I think this too is not a factor. Are all blades set to same pitch? Had the yard check first time at haul out and then had Kiwi check after I pulled the prop. Gotta believe the Kiwi guy knows what he is doing.
Appreciate all the input guys. Easy issues get fixed fast. This is a tough one.
Appreciate all the input guys. Easy issues get fixed fast. This is a tough one.
#1 The Kiwi prop moves the blade centers aft, about 4.5" aft of the front of the hub, when compared to a fixed prop. The Campbell Sailor fixed prop places the blades about 1" aft of the front of the hub, most feathering and folding props move the blade centers aft.
#2 The Universal engines are pretty notorious for having a rough spot in the RPM range which could start the shaft whip.. With the blade centers so far aft of the strut it can be hard to stop once started while maintaining the same/similar RPM.
#3 You also have a soft brass shaft. There is a large difference in resistance to shaft whip with an Aqualoy 22 shaft vs. brass. For example the torsional yield strength of a 1" Aqualoy 22 shaft is approx 87,000 and a brass shaft is approx 15,000 to 22,500 depending upon metallurgy.
#4 The C-36 has a rather long shaft and as such is very sensitive to shaft whip. IMHO that boat should have NEVER had a brass shaft. Converting to an AQ22 shaft was one of the first things I did when we bought our Catalina 36. An AQ22 shaft may not cure the issue but it can certainly help minimize the propensity for jump rope/shaft whip..
Combine these four alone, not even including anode placement, which should be about one thumb length from the strut, and you can induce shaft whip, especially on long shafts..
Questions:
*Was the prop correctly "lap-fit" to the shaft?
*Are you sure the prop is not getting key bound and that it was correctly installed on the taper?
*Does the cutlass (Cutless® if made by Johnson-Duramax) have any play?
*What is the alignment?
*Has fit and facing of the coupling been verified?
*When the shaft was "removed" was a new coupling installed and fitted and faced or did they re-use the old coupling?
#2 The Universal engines are pretty notorious for having a rough spot in the RPM range which could start the shaft whip.. With the blade centers so far aft of the strut it can be hard to stop once started while maintaining the same/similar RPM.
#3 You also have a soft brass shaft. There is a large difference in resistance to shaft whip with an Aqualoy 22 shaft vs. brass. For example the torsional yield strength of a 1" Aqualoy 22 shaft is approx 87,000 and a brass shaft is approx 15,000 to 22,500 depending upon metallurgy.
#4 The C-36 has a rather long shaft and as such is very sensitive to shaft whip. IMHO that boat should have NEVER had a brass shaft. Converting to an AQ22 shaft was one of the first things I did when we bought our Catalina 36. An AQ22 shaft may not cure the issue but it can certainly help minimize the propensity for jump rope/shaft whip..
Combine these four alone, not even including anode placement, which should be about one thumb length from the strut, and you can induce shaft whip, especially on long shafts..
Questions:
*Was the prop correctly "lap-fit" to the shaft?
*Are you sure the prop is not getting key bound and that it was correctly installed on the taper?
*Does the cutlass (Cutless® if made by Johnson-Duramax) have any play?
*What is the alignment?
*Has fit and facing of the coupling been verified?
*When the shaft was "removed" was a new coupling installed and fitted and faced or did they re-use the old coupling?
Many thanks Maine. In reply to your questions -
*No, prop was not lap fit. Had to look up how to do that. Next time I change/remove prop it will be done.
* When I installed Kiwi I did check fit of prop w/o key first then installed with key to same place on shaft.
* Cutlass had no play - I installed new one
* Total re-alignment was done by yard along with new motor mounts. I can only assume it was done correctly along with checking fit & facing of the old coupling. Given the fact that I have no wobble below 1600 or above 2200 rpm with the Kiwi, and no wobble at any rpm with the fixed blade prop I would say coupling and alignment were pretty good, no?
Given all the info though I think my next move is definitely to invest in AQ22 shaft. Additionally, I will move the anode closer to strut as I estimate I am at least an inch away now.
Another question Main, Given my boat, what feathering and or folding prop might work? I am guessing one where the blade centers are not that far aft?
I wish I could make these moves one at a time but I am inclined to purchase the new shaft and prop at the same time, follow above advise, and get on with sailing. As it stands now I think I will just have to stay out of the 1600-2200 rpm range until haul out in the Fall when I can begin making changes.
Thanks.
Checked with MaxProp and they said if prop did not work/perform on my boat within 30 days they would take it back. I also read the installation manual and read that you have to cut the end of the shaft off! Kind of final. One of the good things with the Kiwi (and others, I'm sure) is that you don't have to cut the shaft which is nice since I have switched back to the fixed blade prop more than once.
Thanks Mauruuru. The Kiwi rep mentioned that this too might be the issue.
Ultimately, I think I will eventually replace the bronze shaft with an Aqualoy 22 shaft and look for a feathering prop where blade centers are not as far aft as the Kiwi.
Let me know if you want to sell the kiwi. I may want to test it on my boat. I'm saving for the max prop tho
Les
Les