If there are any you still fighting the cavitation battle I may have gained some insight thur much searching and reading. I though I might pass along what I have found. I came across an article which pretty much covers most aspects of proper prop sizing and placement. This has become a personal quest given that I bought the replacement prop 14/10 to correct the cavitation issue only to have it partially help. Upon pulling my prop this year there was cavitation burning on all the prop tips not to mention the reduction in speed after switching to the 14" prop. The problem would seem to stem from the fact that the prop is to close to the deadwood. As the blades pass behind the deadwood the disturbed water is able to be vaporized by the prop blades at times. Had the drive shaft been a little longer this problem would most likely not exist. As people switch to various feathering and folding props the problem seems to disappear. The reason behind this would be that the design of these props move the blades back and away from the deadwood by 2 to 3". Those of you who may need cutlass replacement and want to stay with fix blade props might want consider replacing the shaft with one which is 1 to 2 inches longer than the factory shaft. If anyone would like a copy of the article which I came across I would be happy to email it to you. Tried to find the article again on the web but that didn't go so well.
At this point I am replacing my cutlass, shaft (new one 1" longer) and prop with Flexofold 15/10. My own personal assault no the cavitation battle.
Prop Cavitation
Moderator: KenKrawford
Re: Prop Cavitation
Happy, Happy, Joy, Joy, Happy, Happy, Joy, Joy. Dropped the boat. New spring loading damper plate, new bronze cutlass, new driveshaft (1" longer), new Flexofold 15-10. The cavitation appears to be a thing of the past. The motor seems quieter with the new style damper. The speed is up by 1 to 1.5 knots with the rpm's at 21-2200 and the engine temp at 173. Motored into a tight steep chop on Sunday we could of never motored into before, never, would of had to motor sail. Not even a hint of cavitation. Yeah.
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leigh weiss
- Posts: 208
- Joined: Mon Mar 05, 2012 7:32 pm
Re: Prop Cavitation
I would like to read the article if you can send it along.
My solution was to replace the prop with the Kiwi Feather Prop and fine tune the pitch for WOT and full rpm.
I Have two sets of blades for this prop. 14" and 15.5"
I have tried both with various pitch settings and settled for the 15.5" prop blades.
This seems to have worked out:
No cavitation noise
WOT = 7+ knots on GPS WOT@3100 RPM (clean bottom, no current, light wind)
I replaced the drive plate with the PYI OEM 22B4, Good results
A Sachs metal Spring Model Better results and the PYI HD Best results as far as low speed transmission chatter.
I can now adjust the idle to 900 rpm down from over 1000.
Leigh Weiss Brisa #155
weiss@rowan.edu
P.S.I still have the PYI 22B4 and the Sachs Drive plates that I used for testing if you need them
My solution was to replace the prop with the Kiwi Feather Prop and fine tune the pitch for WOT and full rpm.
I Have two sets of blades for this prop. 14" and 15.5"
I have tried both with various pitch settings and settled for the 15.5" prop blades.
This seems to have worked out:
No cavitation noise
WOT = 7+ knots on GPS WOT@3100 RPM (clean bottom, no current, light wind)
I replaced the drive plate with the PYI OEM 22B4, Good results
A Sachs metal Spring Model Better results and the PYI HD Best results as far as low speed transmission chatter.
I can now adjust the idle to 900 rpm down from over 1000.
Leigh Weiss Brisa #155
weiss@rowan.edu
P.S.I still have the PYI 22B4 and the Sachs Drive plates that I used for testing if you need them
Last edited by leigh weiss on Wed May 29, 2013 5:49 am, edited 2 times in total.
Leigh and Donna Weiss
Brisa #155
Georgetown, MD. USA
Brisa #155
Georgetown, MD. USA
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digitalvillager
- Posts: 36
- Joined: Mon May 14, 2012 1:23 pm
Re: Prop Cavitation
Poor man's solution to the folding prop......
I was trying to go up the St. John's river after a storm (against the current AND tide) making 1.5 kts on the standard 15/9 when I decided that something could be better. Talked to some friends one of whom offered a 15/12 to try out. Had the diver swap the prop in the water ($75) and could not get above 2700 rpm's at WOT, engine labored. Settled for having my 15/9 prop re-pitched to 15/11 ($135 including sharkskin coating) and another $75 for the diver. WOT is now 3350 and cruising at 2250 with extra rpm's left over. Much better performance, no laboring. Cavitation may still be a problem, but I try not to jamb the throttle in either direction. Biggest problem was the wife being upset by the shiny "new" prop being painted "ugly" black.
I was trying to go up the St. John's river after a storm (against the current AND tide) making 1.5 kts on the standard 15/9 when I decided that something could be better. Talked to some friends one of whom offered a 15/12 to try out. Had the diver swap the prop in the water ($75) and could not get above 2700 rpm's at WOT, engine labored. Settled for having my 15/9 prop re-pitched to 15/11 ($135 including sharkskin coating) and another $75 for the diver. WOT is now 3350 and cruising at 2250 with extra rpm's left over. Much better performance, no laboring. Cavitation may still be a problem, but I try not to jamb the throttle in either direction. Biggest problem was the wife being upset by the shiny "new" prop being painted "ugly" black.
Charlie & Jeanne Monroe
PO Hull #285
Amelia Island, Florida
PO Hull #285
Amelia Island, Florida
Re: Prop Cavitation
Leigh and Yodagwb
Thanks for all the detailed postings on the cavitation probs and folding/feathering props . It sounds like you have both found solutions you are pleased with and I'm trying to decide which one to do. Couple of questions:
on the Flexofold - you extended the shaft 1" do you think that is necessary or does the Flexofold sit back far enough on its own so I could avoid that expense and still eliminate cavitation? You went with a 15-10. Other posters seemed to be suggesting that a 15-10 is a little over propped. What do you think? Are you able to hit 3000 rpm with the 15-10? (I'm assuming that you have the 35b Universal with the 1.88 reduction that I have) Are you in warm salt water? if so have there been any probs dealing with growth and barnacles on the Flexofold? Is it hard to keep clean? Does it require any maintenance?
on the Kiwi- Is there a zinc on it? I've never seen a kiwi in person but the description of set screws and springs makes it sound like a real problem for marine growth here in S Florida. Is it difficult to keep clean? It sounds like it needs to be lubed once a year. Is there other maintenance? Can that be done without pulling the boat out of the water? We don't pull our boat out every year so I don't want to be forced to do it more.
thanks
Bob
Lazy Dog #123
Thanks for all the detailed postings on the cavitation probs and folding/feathering props . It sounds like you have both found solutions you are pleased with and I'm trying to decide which one to do. Couple of questions:
on the Flexofold - you extended the shaft 1" do you think that is necessary or does the Flexofold sit back far enough on its own so I could avoid that expense and still eliminate cavitation? You went with a 15-10. Other posters seemed to be suggesting that a 15-10 is a little over propped. What do you think? Are you able to hit 3000 rpm with the 15-10? (I'm assuming that you have the 35b Universal with the 1.88 reduction that I have) Are you in warm salt water? if so have there been any probs dealing with growth and barnacles on the Flexofold? Is it hard to keep clean? Does it require any maintenance?
on the Kiwi- Is there a zinc on it? I've never seen a kiwi in person but the description of set screws and springs makes it sound like a real problem for marine growth here in S Florida. Is it difficult to keep clean? It sounds like it needs to be lubed once a year. Is there other maintenance? Can that be done without pulling the boat out of the water? We don't pull our boat out every year so I don't want to be forced to do it more.
thanks
Bob
Lazy Dog #123
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leigh weiss
- Posts: 208
- Joined: Mon Mar 05, 2012 7:32 pm
Re: Prop Cavitation
Bob,
I have the KIWI 15.5" prop on my M35B engine with 1.88:1 ratio in upper Chesapeake bay with brackish water but with some marine growth on untreated surfaces.
I have coated the blades and hub with hard racing anti fouling paint. It seems to work well.
The adjustment set screws are not a regular maintenance item and the greasing requirement is once a year at haul out.
I have used my small hand grease gun with grease needle under water to see if it could be done. It works but you have to be careful not to drop the screws (3) that are plugs for the grease ports one on each blade. It took about 15 min.
The prop sets further back from the dead wood and does not create cavitation noises. I have installed a zinc collar between the front of the prop hub and the end of the cutlass bearing.
The reversing spring is internal to the assembly and does not provide any problem with respect to growth.
Russ Peel has a good picture of the zinc install.
I have a spare set of blades (for the past few years) if I should need to replace one. This can be done in the water!!!
So far so good!
I have hit all kinds of unseen/seen things with no damage.
One spare blade came with the prop when I ordered it because of the Boat show special.
The other blades I ordered when my friend ordered two props for his cat. He also got some spare blades.
His like mine are sitting as insurance.
Let us know what you decide and if you like the increased sailing performance from a feathering prop.
I still shift the transmission into reverse whilst sailing. The shaft will rotate slightly when sailing over 5 Kn.
Leigh Weiss Brisa #155
Upper Chesapeake Bay
I have the KIWI 15.5" prop on my M35B engine with 1.88:1 ratio in upper Chesapeake bay with brackish water but with some marine growth on untreated surfaces.
I have coated the blades and hub with hard racing anti fouling paint. It seems to work well.
The adjustment set screws are not a regular maintenance item and the greasing requirement is once a year at haul out.
I have used my small hand grease gun with grease needle under water to see if it could be done. It works but you have to be careful not to drop the screws (3) that are plugs for the grease ports one on each blade. It took about 15 min.
The prop sets further back from the dead wood and does not create cavitation noises. I have installed a zinc collar between the front of the prop hub and the end of the cutlass bearing.
The reversing spring is internal to the assembly and does not provide any problem with respect to growth.
Russ Peel has a good picture of the zinc install.
I have a spare set of blades (for the past few years) if I should need to replace one. This can be done in the water!!!
So far so good!
I have hit all kinds of unseen/seen things with no damage.
One spare blade came with the prop when I ordered it because of the Boat show special.
The other blades I ordered when my friend ordered two props for his cat. He also got some spare blades.
His like mine are sitting as insurance.
Let us know what you decide and if you like the increased sailing performance from a feathering prop.
I still shift the transmission into reverse whilst sailing. The shaft will rotate slightly when sailing over 5 Kn.
Leigh Weiss Brisa #155
Upper Chesapeake Bay
Leigh and Donna Weiss
Brisa #155
Georgetown, MD. USA
Brisa #155
Georgetown, MD. USA
Re: Prop Cavitation
Bob
I most likely did not have to extend the shaft but I had to cut it out any way to replace the cutlass bearing without dropping the rudder. The design if the prop should put the blades far enough behind the deadwood to stop the cavitation. With the 15-10 my max RPM are now 2900 underload and 3000 no load. I am good with that. I am in salt water, Chesapeake, and a friend of mind has had a flexoflod for years. The only thing he does is to paint it with a zinc bottom paint before he drops it in the spring. In reading the instructions that came with the prop it really doesn't need any maintenance. They even say it does not need to be lubed. I seem to be moving at 6.3knts at 2300prms and the engine temp is at 170, maybe be a touch above that but its hard to tell with the gauge. It is definetly below the 180 mark.
I most likely did not have to extend the shaft but I had to cut it out any way to replace the cutlass bearing without dropping the rudder. The design if the prop should put the blades far enough behind the deadwood to stop the cavitation. With the 15-10 my max RPM are now 2900 underload and 3000 no load. I am good with that. I am in salt water, Chesapeake, and a friend of mind has had a flexoflod for years. The only thing he does is to paint it with a zinc bottom paint before he drops it in the spring. In reading the instructions that came with the prop it really doesn't need any maintenance. They even say it does not need to be lubed. I seem to be moving at 6.3knts at 2300prms and the engine temp is at 170, maybe be a touch above that but its hard to tell with the gauge. It is definetly below the 180 mark.
Re: Prop Cavitation
Bob
Missed a couple of facts, sorry. Yes, I have the Universal 35B with a 1.88 trans. Also at the 2900rpms, WOT, I was seeing 7.5knts but could see the engine temp starting to creep up toward the 180 mark.
Missed a couple of facts, sorry. Yes, I have the Universal 35B with a 1.88 trans. Also at the 2900rpms, WOT, I was seeing 7.5knts but could see the engine temp starting to creep up toward the 180 mark.
Re: Prop Cavitation
Hi Yodagbw (sorry, don't know any more about you),
Leigh has used the PYI OEM 22B4 damper plate and is very happy with it. Which damper plate did you use? I am looking at changing damper plate, PPS bellows, cutlass bearing in next few months and need to a) identify best option for damper plate and b) land in Australia ready for installation so currently gathering as much info as I can.
Cheers
Russ Peel
Avalon #150
Leigh has used the PYI OEM 22B4 damper plate and is very happy with it. Which damper plate did you use? I am looking at changing damper plate, PPS bellows, cutlass bearing in next few months and need to a) identify best option for damper plate and b) land in Australia ready for installation so currently gathering as much info as I can.
Cheers
Russ Peel
Avalon #150
Russ Peel
Avalon #150
Avalon #150
Re: Prop Cavitation
Russ
Don't know the model number off hand but I used the damper plate which has the two sets of different sized springs.
Don't know the model number off hand but I used the damper plate which has the two sets of different sized springs.
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leigh weiss
- Posts: 208
- Joined: Mon Mar 05, 2012 7:32 pm
Re: Prop Cavitation
Russ, I used all three damper plates and found the best one for my boat and engine. The High Deflection PYI damper was the best. I have a new Sachs spring type and PYI R&D 22B4 damper that I tried and did not use.
Leigh Weiss
Brisa #155
Upper Chesapeake Bay
Leigh Weiss
Brisa #155
Upper Chesapeake Bay
Leigh and Donna Weiss
Brisa #155
Georgetown, MD. USA
Brisa #155
Georgetown, MD. USA
Re: Prop Cavitation
Leigh,
Do you have a part number for the high deflection PYI damper plate? What do you like about it versus the SACHS spring style model that you seemed to like in an earlier post?
We have some rattle or chatter from idle speed to about 1700 RPM, and since reading about the damper plates on this board I am thinking this could be the issue. It's always been there since we bought the boat 2 years ago (with 450 hours) and I thought it was just a normal sound (something like the rattling/vibrating of an outboard that smooths out when you increase the throttle). We now have about 700 hours and I am considering replacing the damper plate just on general principals. $200 and a days work seems like a good deal for some peace of mind. Would a completely destroyed damper plate result in not being able to put the engine in gear at all, leaving you stranded, or would it just sound like the world is coming apart under your feet?
Thanks
Do you have a part number for the high deflection PYI damper plate? What do you like about it versus the SACHS spring style model that you seemed to like in an earlier post?
We have some rattle or chatter from idle speed to about 1700 RPM, and since reading about the damper plates on this board I am thinking this could be the issue. It's always been there since we bought the boat 2 years ago (with 450 hours) and I thought it was just a normal sound (something like the rattling/vibrating of an outboard that smooths out when you increase the throttle). We now have about 700 hours and I am considering replacing the damper plate just on general principals. $200 and a days work seems like a good deal for some peace of mind. Would a completely destroyed damper plate result in not being able to put the engine in gear at all, leaving you stranded, or would it just sound like the world is coming apart under your feet?
Thanks
Gary & Janet
The Best of Times (Hull #422)
The Best of Times (Hull #422)
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leigh weiss
- Posts: 208
- Joined: Mon Mar 05, 2012 7:32 pm
Re: Prop Cavitation
Russ, Gary & Janet,
I first replaced my Damper with a Sachs and reported marked improvement of the chatter at low speed. I went on to try a new R&D 22B4 and upon the recommendation of the PYI engineer I tried the High Deflection Damper and concluded this was the best.
( so now I have a collection of Damper plates)
I mentioned the HD damper plate stock number in an earlier post. It replaces the R&D 22B4 and was in stock from PYI
Send them an e-mail for the complete number and any ordering instructions for shipping to you.
If the damper plate fails it is the link of all power from the engine to the transmission. Failure might mean no go!
I think it is prudent for you to pick this time to replace the Damper. Posts on this and other sites suggest these damper plates fail at around 1000 hours and in some cases much sooner.I can't help thinking that the chattering on the internal parts of the transmission does contribute to degrading it's life.
This is a good winter project. Keep us posted!
I first replaced my Damper with a Sachs and reported marked improvement of the chatter at low speed. I went on to try a new R&D 22B4 and upon the recommendation of the PYI engineer I tried the High Deflection Damper and concluded this was the best.
( so now I have a collection of Damper plates)
I mentioned the HD damper plate stock number in an earlier post. It replaces the R&D 22B4 and was in stock from PYI
Send them an e-mail for the complete number and any ordering instructions for shipping to you.
If the damper plate fails it is the link of all power from the engine to the transmission. Failure might mean no go!
I think it is prudent for you to pick this time to replace the Damper. Posts on this and other sites suggest these damper plates fail at around 1000 hours and in some cases much sooner.I can't help thinking that the chattering on the internal parts of the transmission does contribute to degrading it's life.
This is a good winter project. Keep us posted!
Leigh and Donna Weiss
Brisa #155
Georgetown, MD. USA
Brisa #155
Georgetown, MD. USA
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MorningStar
Re: Prop Cavitation
yodagwb,
I'm inquiring about the Flexofold 15-10 prop. You've had a season with this prop and I question are you still pleased with the performance. I'm considering the Flexofold, it has the best ratings for cruising speed. At you still able to get 7 plus knots at 2900 rpm.. WOT? Any maintenance issues? Did you order it through the US distributor? Do you think the extended shaft length made much of a difference? Appreciate any comments on your experience this summer with the new prop.
Thanks,
Barry Dupuy
Morning Star #35
Kemah, TX
I'm inquiring about the Flexofold 15-10 prop. You've had a season with this prop and I question are you still pleased with the performance. I'm considering the Flexofold, it has the best ratings for cruising speed. At you still able to get 7 plus knots at 2900 rpm.. WOT? Any maintenance issues? Did you order it through the US distributor? Do you think the extended shaft length made much of a difference? Appreciate any comments on your experience this summer with the new prop.
Thanks,
Barry Dupuy
Morning Star #35
Kemah, TX
Re: Prop Cavitation
I bought that same Flexo-fold prop about two years ago and have been very happy with it. Still get great performance. Would definitely buy it again.
Can't speak to an 'extended shaft' since I'm not sure what you're referring to there. Hope that helps.
Can't speak to an 'extended shaft' since I'm not sure what you're referring to there. Hope that helps.
Phil
Paramethia
Hull #55
Paramethia
Hull #55
Re: Prop Cavitation
I love the prop. I have the Universal engine so 2900 is not our cruising rpm, ours is in the 2000-2400 range. Before the switch it was a struggle to hit 6-6.25 mph at 2400 rpms. With the new prop I do 7mph at 2200rpm no problem. It did every thing I hoped it would. According to the manufacturer there is no maintenance, no greasing, nothing, nice. I most likely did not have to extend the shaft, that was more of a buck shot approach to the cavitation issues I was having. We weight 23,000lbs, both the boat and myself are in serious need of a diet, which most definitely doesn't help our speed. We are currently heading to Florida and spent Oct 8 pounding into some serious slop in the Pamlico Sound at Maws point. Don't think we could have done it with the fixed 14-10, as it was we crashed into some wave sets that slapped use down to 3mph only to have to fight are way back up. I ordered the prop from the manufacture. Noticed as far as fuel consumption the we were burning .75/hr at 2200rpm doing 7mph+ or - as we backed it down to 1800rpms doing 6mph+ or -, in the Dismal Swamp, our burn rate was closer to .5/hr. From the sound of things you have a Yanmar and they are geared differently so you do need to check with Flexofold as to the proper size and pitch. Long and short, DO IT, pull the trigger. The only question you will have is "Why didn't I do this sooner".
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saileagleswings
- Posts: 46
- Joined: Mon Sep 10, 2007 8:46 am
- Location: Punta Gorda Fl
- Contact:
Re: Prop Cavitation
Did you mean mph or kts? 6.25 mph is only 5.4 kts.
Re: Prop Cavitation
I meant mph. Pretty sad. When I pulled the boat last year there where cavitation burn marks on the blade tips. Knowing I had a 1200 mile trip to Florida come up set me into a panic to identify and correct the problem. Catalina had taken a shot at it and missed, now I figured it was up to me. Much reading brought me to the conclusion the problems were the weight, beam and the deadwood. In all honesty the prop should probably be a 16" prop given the the size and weight of the boat, but Flexofold doesn't make a 16-8 or 9 unit and a 16-10 would have been to much for the motor to handle. For the weight and beam of the boat, the boat is a bit under powered. The Universal 35 is a 30hp engine. With a Yanmar I have no doubts the speeds you will see across the board will be greater than mine.
Re: Prop Cavitation
Barry
Sorry just notice you have hull 35 so you would have the Universal engine. Yes I can till get the speed up to 7+ knots WOT, but after a short period on time the the engine temp will start to rise, I like to run in the 170 to 175 degree range. The 15-10 is most likely a tad over propped but I feel I make up for it at the lower rpms. Flexofold recommends a 15-9. We were behind a 40+ foot HR for a while and he was taking his time, saving on fuel I guess. We were running at 1700rpms doing 6 +/-mph and burning maybe .5g/h. Wish I had the patience to do that all the time. Like I said at 2200 rpms I am seeing 7+ mph, no current. You will have to excuse the fact I am dealing in mph, that is what my setting are scaled to given the ICW info is done in Statute Miles. I do see posting of people claiming they run at 7+knots most of the time with out a problem. I have numerous questions regarding that. Again I am only able to speak to the Universal, as that is the engine I have and I try not to beat it to much. Would I buy it again? In a heart beat, only 9 years sooner.
Sorry just notice you have hull 35 so you would have the Universal engine. Yes I can till get the speed up to 7+ knots WOT, but after a short period on time the the engine temp will start to rise, I like to run in the 170 to 175 degree range. The 15-10 is most likely a tad over propped but I feel I make up for it at the lower rpms. Flexofold recommends a 15-9. We were behind a 40+ foot HR for a while and he was taking his time, saving on fuel I guess. We were running at 1700rpms doing 6 +/-mph and burning maybe .5g/h. Wish I had the patience to do that all the time. Like I said at 2200 rpms I am seeing 7+ mph, no current. You will have to excuse the fact I am dealing in mph, that is what my setting are scaled to given the ICW info is done in Statute Miles. I do see posting of people claiming they run at 7+knots most of the time with out a problem. I have numerous questions regarding that. Again I am only able to speak to the Universal, as that is the engine I have and I try not to beat it to much. Would I buy it again? In a heart beat, only 9 years sooner.
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MorningStar
Re: Prop Cavitation
yodagwb
Appreciate the input. Still seriously considering the Flexofold 15X10.
Appreciate the input. Still seriously considering the Flexofold 15X10.