Re: Stus-List Awful Vibration - now transmission cable adjustment

[John and Maryann Read via CnC-List]

We had similar issues with our 3GM30 with Kanzaki transmission about 5 years 
ago.  The shaft was not turning fast enough until RPM’s got up to a certain 
point then would sort of fully engage but the blades were not symmetrically 
deployed causing the vibration.  Cause was the transmission cone and matching 
part were not quite fully engaged causing a polishing and slippage.  Very long 
story short, got it rebuilt twice – the first guy messed it up and is now fine. 
 An essential element of the rebuild is to ensure the shift lever is properly 
shimmed so the cone is fully engaged at the lever stop – a skill I am told only 
a mechanic with Kanzaki experience really understands



An essential item of this is to ensure the spring loaded attachment on the 
cable end is properly adjusted such that the lever on the transmission is fully 
engaged before the lever on the pedestal reaches its end of travel  in both 
forward and reverse.  In other words, when the transmission is fully in gear 
you have additional travel of the pedestal lever before its end of travel.  You 
can feel the spring resistance.  In our case, using the bracket on the engine, 
we set the cable so that at neutral the pedestal lever was at mid point.  There 
are two attachment holes on the transmission lever.  We use the inner one as 
the outer one has too much travel to permit the spring action.  A recommended 
annual maintenance item is to put a drop or two of oil into this spring and 
ensure it moves freely in both directions.



My two cents American



John and Maryann

Legacy III

1982 C 34

Noank, CT



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Re: Stus-List Awful Vibration

[Dave via CnC-List]

Tom, 

That's exactly my problem. If the blades are moving freely then that's probably 
not the problem. I'll be checking to see if my gear shift is moving the 
transmission into fully engaged forward tomorrow. If that's the issue I'll 
certainly let you know. If it's not then I'm not sure what to do except call 
the transmission guy again. 

Dave J 
Saltaire 
C 35Mk3 
Bristol, RI 


- Original Message -

From: "Tom Lynch" <thomasmly...@gmail.com> 
To: cnc-list@cnc-list.com 
Cc: "ALAN BERGEN" <trya...@alumni.usc.edu>, davidjaco...@comcast.net 
Sent: Friday, June 17, 2016 1:28:48 PM 
Subject: Re: Stus-List Awful Vibration 

Dave, 

What you are describing is the same thing that is happening on my 1985 33 MKII 
with Yanmar 2GM20. I have a folding martek prop and when I leave my slip the 
blades open (No vibration ) but anytime I slow the boat down like when I'm 
coming back to the marina and I throttle down while still in forward gear the 
blades Close ?? (I'll get a nasty vibration) and the only way to stop the 
vibration is to shift into reverse stop the boat and shift back to forward. 

This is especially cumbersome when out sailing and taking down sails with 
forward momentum and when I run the engine and shift to forward, I'll get the 
nasty vibration, the vibration stops only when I shift to reverse until I 
completely get stopped and then I can shift to forward and no vibration. 

What I was planning to do was send the prop to martec for refurbishing at the 
end of this season; however, now after what I'm reading this thread I'm not so 
sure that is the right solution. When inspecting the prop before launch this 
spring, the blades easily opened and closed by hand. 

I'm now thinking that the problem may be with the shaft spinning to slowly or 
transmission not fully engaged. Sorry that I'm not offering any new solutions 
here but just commiserating. 

Tom Lynch 
Bayfield WI 
IndoIrish 

On Thu, Jun 16, 2016 at 10:48 AM, Dave via CnC-List < cnc-list@cnc-list.com > 
wrote: 



Alan, 

My gear shift linkage is totally different with the cable coming in from 
forward of the lever through a bracket. Its pretty obvious that I need only to 
remove the lever rotate it 180 degrees and reattach it to make forward be 
forward again. 

I'm guessing that if the vibration was due to misalignment, engine mounts, 
bearing or bent shaft that the vibration would always be their and not only 
after slowing down. The prop, which is what I thought the issue was, has been 
replaces with a brand new geared prop and since a new prop didn't fix the 
problem that's not it. 

I did find the following on the web; 



My prop opens easily by hand and when the blades are oriented properly the 
lower one will hang down by its own weight. Given that data, I knew with 
absolute certainty that if it spins, it has to open. The condition Bob and Dyk 
are describing happened to me just after I reinstalled the engine after 
rebuilding it and I had not adjusted the linkage properly. I would have to rev 
the engine up around 1500-1800 and it would rumble and abruptly "kerchunk" and 
churn water at the stern. Initially I thought that was the prop opening, but 
knowing how loose the prop was I knew there was no reason for it to be closed 
before that. So I looked at the shaft. When put into gear, it would spin but so 
slowly that there wasn't enough revolution to drive the boat. I pushed on the 
linkage lever on the transmission and wham it fully engaged and the shaft 
started spinning like it should - much faster. I realized the rumbling I heard 
was gears trying to mesh and the kerchunk I had heard was the transmission 
popping into gear, not the prop opening. I adjusted the linakge so now when I 
shift into forward, the boat moves even at low RPMs. 

Dyk, Bob, I don't know how tight a brand new or recently rebuilt prop is 
supposed to be, but a spinning mass generates quite a bit of force. The formula 
for centripetal force is F=mv^2/r with m=mass of object, v=velocity at a 
certain radius, and r= radius. A quick check of the numbers will tell you that 
even at low RPM, there is easily enough force to open your prop. Keep in mind 
that if it is so tight that it won't open, it shouldn't be able to close 
either, so when sailing an open prop should be spinning like mad and you can 
hear and feel that. If you can assure yourself that the prop is opening and 
closing, the only other variable in the equation is the RPM of the shaft. I can 
only speak from my own experience and what worked for me but there is no reason 
I can think of for a clean, properly adjusted prop to not open. It has been 
designed to open when it revolves. Good luck! 



Dyk Luben 

unregistered posted 09-13-2002 02:36 PM 

 

I need to follow up on my propeller situation. After further study, I found 
that indeed the propeller shaft was spinning too slowly. It was a prob

Re: Stus-List Awful Vibration

[Dave via CnC-List]

Alan, 

My gear shift linkage is totally different with the cable coming in from 
forward of the lever through a bracket. Its pretty obvious that I need only to 
remove the lever rotate it 180 degrees and reattach it to make forward be 
forward again. 

I'm guessing that if the vibration was due to misalignment, engine mounts, 
bearing or bent shaft that the vibration would always be their and not only 
after slowing down. The prop, which is what I thought the issue was, has been 
replaces with a brand new geared prop and since a new prop didn't fix the 
problem that's not it. 

I did find the following on the web; 



My prop opens easily by hand and when the blades are oriented properly the 
lower one will hang down by its own weight. Given that data, I knew with 
absolute certainty that if it spins, it has to open. The condition Bob and Dyk 
are describing happened to me just after I reinstalled the engine after 
rebuilding it and I had not adjusted the linkage properly. I would have to rev 
the engine up around 1500-1800 and it would rumble and abruptly "kerchunk" and 
churn water at the stern. Initially I thought that was the prop opening, but 
knowing how loose the prop was I knew there was no reason for it to be closed 
before that. So I looked at the shaft. When put into gear, it would spin but so 
slowly that there wasn't enough revolution to drive the boat. I pushed on the 
linkage lever on the transmission and wham it fully engaged and the shaft 
started spinning like it should - much faster. I realized the rumbling I heard 
was gears trying to mesh and the kerchunk I had heard was the transmission 
popping into gear, not the prop opening. I adjusted the linakge so now when I 
shift into forward, the boat moves even at low RPMs. 

Dyk, Bob, I don't know how tight a brand new or recently rebuilt prop is 
supposed to be, but a spinning mass generates quite a bit of force. The formula 
for centripetal force is F=mv^2/r with m=mass of object, v=velocity at a 
certain radius, and r= radius. A quick check of the numbers will tell you that 
even at low RPM, there is easily enough force to open your prop. Keep in mind 
that if it is so tight that it won't open, it shouldn't be able to close 
either, so when sailing an open prop should be spinning like mad and you can 
hear and feel that. If you can assure yourself that the prop is opening and 
closing, the only other variable in the equation is the RPM of the shaft. I can 
only speak from my own experience and what worked for me but there is no reason 
I can think of for a clean, properly adjusted prop to not open. It has been 
designed to open when it revolves. Good luck! 



Dyk Luben 

unregistered posted 09-13-2002 02:36 PM 

 

I need to follow up on my propeller situation. After further study, I found 
that indeed the propeller shaft was spinning too slowly. It was a problem in 
what I called the transmission, but what the professionals call the reversing 
gear. The clutch was worn out and no amount of linkage adjustment would correct 
it. I had a new clutch and seals installed by Mack Boring, and it works 
perfectly now. So if anyone assumes that their propeller is not opening 
correctly, don't go buy a new prop like I did, but check first that the clutch 
is fully engaging 

Since I had the transmission rebuilt it's probably not the transmission itself 
but may be that the shift lever throw isn't long enough and its not fully 
engaging. So, reversing the lever arm and checking to see if the transmission 
is fully engaging (by shifting it into gear at the transmission) is my next 
step. 

By the way, last night was the first time the sails were hoisted and the boat 
sailed and we managed to win line honors and a second place finish against 
others for whom its their 3rd race. 

Dave J 
Saltaire 
C 35Mk3 
Bristol, RI 
- Original Message -

From: "ALAN BERGEN"  
To: davidjaco...@comcast.net 
Sent: Tuesday, June 14, 2016 10:50:10 PM 
Subject: Awful Vibration 

Dave: 

This is how the shift cable linkage should look. The vibration could be: prop 
out of balance, bad engine mounts, bad cutlass bearing, bent shaft, prop blades 
not opening all the way. 

I replaced my folding, two blade Gori prop with a three blade Maxi prop. 
Expensive, but well worth it. No vibration and good stopping action in reverse. 

My engine is a 3GM f (20 hp). 

Alan Bergen 
35 Mk III Thirsty 
Rose City YC 
Portland, OR 

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Stus-List Awful vibration

[Jean-Francois J Rivard via CnC-List]

> 
> 
> +1 on double checking the pitch. When I had my Martec refurbished I was told 
> by Martec that my original blades were under pitched and I bought new blades 
> with higher pitch..
> 
> After a year of chasing vibration checking everything with no success I 
> finally had my old blades machined to fit  the new pivot and slapped them 
> on..   Problem solved! 
> 
> Cavitation was the culprit.  The offending blades were also pretty badly 
> pitted which corroborated the cavitation theory.  
> 
> Good luck with it 
> 
> -Francois 
> 
> 1990 34+ "Take Five"
> Lake Lanier GA 
> 
> 
> 
> Sent from IBM Verse

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Re: Stus-List Awful vibration

[Nauset Beach via CnC-List]

Dave,

 

A couple other things to explore beyond the engine / shaft alignment already 
mentioned: 

 

A possibility might be the hub of the Flex prop is not seated properly on the 
shaft and therefore is off center.  If the key moved out of position as you 
slid the hub on, the hub could ride up on it and not be fully on the shaft.  

 

The cutlass bearing may be worn, especially if it had several years of 
operation with that out of balance Martec prop.  Try to dive on the boat and 
see if you can move the shaft at the strut.  A rule of thumb I heard years ago 
is anything more than 1/16” of play is too much and the cutlass needs to be 
replaced.  

 

Another possibility is the shaft is not true.  The prior owner might have 
caught a lobster pot or other line and bent the shaft.  

 

While the prop could be reset while in the water it would require a 
knowledgeable diver and some of the pre-coated set screws that came from Flex o 
Fold with the prop.  Otherwise, a short haul is in order, or living with it and 
chase down the cause(s) after hauling for the winter.  

 

I did get the 16x12 blades for my old Flex hub [replacing the 16x13 blades 
originally sold to me] and it made a significant difference in reducing 
vibration.  

 

Good luck

Brian

 

From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Robin Drew 
via CnC-List
Sent: Tuesday, June 14, 2016 10:39 PM
To: cnc-list@cnc-list.com
Cc: Robin Drew <cncforum.ro...@gmail.com>
Subject: Re: Stus-List Awful vibration

 

Did you check you engine/ shaft alignment? It's a common cause of vibration.

Robin


On Jun 14, 2016, at 8:55 PM, Dave via CnC-List <cnc-list@cnc-list.com 
<mailto:cnc-list@cnc-list.com> > wrote:

I purchased my boat, a 1984 35Mk3 three years ago. The first season the boat 
would vibrate badly when I'd slow down under power. I'd put it in reverse, 
throw it into forward (ouch) and things would be fine. The blades always opened 
initially when I motored off the mooring but if I slowed down the flow over the 
blades exceeded the centripetal force and folded one of the blades and not the 
other . So, that winter I sent the 2 bladed prop back to Martek to have it 
rebuilt. They said the blades were so badly oxidized that they couldn't weld 
them to build up the stops so, they replaced the blades with another pair 
(used) they had available. To be sure the problem was fixed I also had the cone 
clutch in the transmission replaced. Last summer the only thing that changed 
was that the boat now moved forward when the lever was pulled back to reverse 
and visa versa. The vibration still happened under the same scenarios. Having 
had the blades replaced and the transmission rebuilt there was no way to tell 
whether it was that the blades were the opposite hand as what I had previously 
or if the transmission was done incorrectly.

 

This spring I purchased a 2 blade Flexfold geared prop and guess what, the 
vibration problem is still there and forward and reverse are still, yep 
reversed. So, I know that the direction issue is the transmission and that is 
easily fixed by rotating the linkage arm. But, I'm totally baffled as to why 
the vibration problem has not been resolved.

 

So, if anyone has any suggestions or ideas they would be greatly appreciated.

 

Dave J

Saltaire

C 35Mk3

Bristol, RI

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This list is supported by the generous donations of our members. If you like 
what we do, please help us pay for our costs by donating. All Contributions are 
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Re: Stus-List Awful vibration

[Robin Drew via CnC-List]

Did you check you engine/ shaft alignment? It's a common cause of vibration.
Robin

> On Jun 14, 2016, at 8:55 PM, Dave via CnC-List  wrote:
> 
> I purchased my boat, a 1984 35Mk3 three years ago. The first season the boat 
> would vibrate badly when I'd slow down under power. I'd put it in reverse, 
> throw it into forward (ouch) and things would be fine. The blades always 
> opened initially when I motored off the mooring but if I slowed down the flow 
> over the blades exceeded the centripetal force and folded one of the blades 
> and not the other . So, that winter I sent the 2 bladed prop back to Martek 
> to have it rebuilt. They said the blades were so badly oxidized that they 
> couldn't weld them to build up the stops so, they replaced the blades with 
> another pair (used) they had available. To be sure the problem was fixed I 
> also had the cone clutch in the transmission replaced. Last summer the only 
> thing that changed was that the boat now moved forward when the lever was 
> pulled back to reverse and visa versa. The vibration still happened under the 
> same scenarios. Having had the blades replaced and the transmission rebuilt 
> there was no way to tell whether it was that the blades were the opposite 
> hand as what I had previously or if the transmission was done incorrectly.
> 
> This spring I purchased a 2 blade Flexfold geared prop and guess what, the 
> vibration problem is still there and forward and reverse are still, yep 
> reversed. So, I know that the direction issue is the transmission and that is 
> easily fixed by rotating the linkage arm. But, I'm totally baffled as to why 
> the vibration problem has not been resolved.
> 
> So, if anyone has any suggestions or ideas they would be greatly appreciated.
> 
> Dave J
> Saltaire
> C 35Mk3
> Bristol, RI
> ___
> 
> This list is supported by the generous donations of our members. If you like 
> what we do, please help us pay for our costs by donating. All Contributions 
> are greatly appreciated!
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This list is supported by the generous donations of our members. If you like 
what we do, please help us pay for our costs by donating. All Contributions are 
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Stus-List Awful vibration

[Dave via CnC-List]

I purchased my boat, a 1984 35Mk3 three years ago. The first season the boat 
would vibrate badly when I'd slow down under power. I'd put it in reverse, 
throw it into forward (ouch) and things would be fine. The blades always opened 
initially when I motored off the mooring but if I slowed down the flow over the 
blades exceeded the centripetal force and folded one of the blades and not the 
other . So, that winter I sent the 2 bladed prop back to Martek to have it 
rebuilt. They said the blades were so badly oxidized that they couldn't weld 
them to build up the stops so, they replaced the blades with another pair 
(used) they had available. To be sure the problem was fixed I also had the cone 
clutch in the transmission replaced. Last summer the only thing that changed 
was that the boat now moved forward when the lever was pulled back to reverse 
and visa versa. The vibration still happened under the same scenarios. Having 
had the blades replaced and the transmission rebuilt there was no way to tell 
whether it was that the blades were the opposite hand as what I had previously 
or if the transmission was done incorrectly. 

This spring I purchased a 2 blade Flexfold geared prop and guess what, the 
vibration problem is still there and forward and reverse are still, yep 
reversed. So, I know that the direction issue is the transmission and that is 
easily fixed by rotating the linkage arm. But, I'm totally baffled as to why 
the vibration problem has not been resolved. 

So, if anyone has any suggestions or ideas they would be greatly appreciated. 

Dave J 
Saltaire 
C 35Mk3 
Bristol, RI 
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