Catalina 34

General Activities => Main Message Board => Topic started by: kerk fisher on October 08, 2013, 04:03:23 PM

Title: boat pulling to port when using motor!! Distress!
Post by: kerk fisher on October 08, 2013, 04:03:23 PM
This year, for the first time, our boat pulls to port pretty drastically when the motor is on. When moving slowly we don't feel it but as we pick up speed we need to need to struggle to keep it going straight.  Does not happen while under sail.  There was no trauma to the rudder, and we have a new stainless shaft. Propeller good.  Visual inspection down below indicated no problem apparently with steering mechanism, gears, all tight, running freely. Yard put boat to bed very well.  Last year no problem at all. But this year..... What happened and is happening?
Title: Re: boat pulling to port when using motor!! Distress!
Post by: mregan on October 08, 2013, 04:23:06 PM
Mine does that all the time.  I think it has to do with the water flowing by the rudder.  I think it's pretty typical
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Clay Greene on October 08, 2013, 05:04:06 PM
Prop walk in forward should cause the boat to turn to port slightly but it should be more noticeable at low speeds rather than high speeds.  Once you get water flowing over the rudder, your rudder control should make the prop walk disappear.  That is inconsistent with what you are reporting, more pull to port as boat speed increases.  And the amount of prop walk wouldn't change from year to year unless something changed with the prop, which is my suspicion.  What type of prop do you have? 
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Jim Hardesty on October 08, 2013, 05:22:53 PM
I think you are talking about "prop-walk".  Shamrock has a noticeable pull to port in reverse, less noticeable to starbord in forward.  When enough water starts flowing over the rudder ie a bit of speed, the prop-walk is much less.  If the boat is taken out of gear, the prop-walk stops.  So can backup about straight by taking the boat in then out of gear as soon as getting a little way on.  The only things that I can think of that would change how much prop-walk a boat gets are.  Changing the prop or repitching the prop, more pitch more walk.  Engine idle speed, higher more, lower less.
Does that sound like what you have?  If so it's normal.  If the wheel always needs to be turned to keep the boat straight when motoring and not sailing it's something else.  And to be noticeable think that it would more than a little.  When the boat gets lifted check rudder play, the cutless bearing and the cutless bearing support.
Hope it's nothing or something minor. And this helped.
Jim
Title: Re: boat pulling to port when using motor!! Distress!
Post by: kerk fisher on October 08, 2013, 05:51:34 PM
Thanks for your responses. We have the usual prop walk in reverse.  But this problem is in forward.  The prop is three blade; the shaft and cutless bearing were replaced a couple of years ago.  I'll be at the boat in a couple of weeks and can check the prop, etc more carefully but I know that the boat was motoring fine at the end of last season and this started right at the beginning of this season.  What could have happened?  And this is MORE than a little.  The autohelm will not hold because of this, so I"ve used a rope to keep the wheel straight!!
Title: Re: boat pulling to port when using motor!! Distress!
Post by: prh77 on October 09, 2013, 05:03:56 AM
Could the rudder shaft have been bent during haul/launch? Sounds like a trim problem as we say in aviation.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Jim Hardesty on October 09, 2013, 06:16:35 AM
To the bent rudder shaft, I would suggest that may be the shaft strut got damaged or bent at lift/out or lift/in.

If this happened just after the shaft and cutless bearing were replaced thats where I'd start looking first. If so my guess is the shaft is out of alignment, a lot.  A few of things that I can think of are,  a bent or broken shaft strut,  broken or loose engine mounts,  and bad engine alignment.   All should have been checked when the shaft and cutless bearing were replaced.

You didn't mention any vibration.  Do you have any?
   
With having to use a rope to keep the boat straight.  This is not something that I would live with and continue to use the boat till I found the cause.

Jim
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Clay Greene on October 09, 2013, 11:33:11 AM
Don't think it could be the rudder or the steering system if it is not happening under sail.  It would have to be the propeller shaft, the strut or the propeller.  Interesting in that you say you haven't noticed an increase in the prop walk in reverse - I would think that whatever is causing the port pull of the bow in forward would increase the port pull of the stern in reverse. 

I'll be interested to hear the answer when you figure it out - it's a puzzler. 
Title: Re: boat pulling to port when using motor!! Distress!
Post by: scotty on October 09, 2013, 01:25:13 PM
It seems significant that this happens when the speed is increased.  Something is tweeking out of line.  It sounds like you should get on this ASAP (it could get worse).  I agree with Jim that this is not something you should have to live with.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Ron Hill on October 09, 2013, 02:55:49 PM
Kerk : Not too sure as what to advise??  If your shaft were out of alignment the vibration would be VERY evident.  Take a look at the play between the rudder and the locked wheel.  

Bothers me that the Autohelm will not hold it and it's something that just happened this year!?!

Check that rudder play and let us know.   :?
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Jim Hardesty on October 09, 2013, 05:00:41 PM
Kerk,
Pardon me for treating your real and potentially serious problem as a bit of a "brain teaser".   After some thought my idea about shaft alignment and/or strut problems doesn't' hold up for two reasons.  First, the vibration would be bad.   Second, many if not most boats are built with the shaft at an angle, helps with prop-walk and shaft removal.  The steering has little or no pull.
So,  another thought is rudder delamination.  With the propwash the delamination opens up and changes the rudder shape and it pulls.  More RPM more pull.  At sailing speed with no prop wash the delamination isn't opening, at least not as much, and isn't noticeable.  Does that sound like what's going on?
Just my thoughts, the problem may be evident  and a fix started when the boat is lifted for winter storage.  Please let us know.
Jim
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Roc on October 10, 2013, 03:58:46 AM
What you're seeing is "prop walk" in forward, which is typical.  In reverse, prop spins counterclockwise.  The blades bite into the water and will pull the stern to port.  Typical for a 3-blade prop. In forward, prop spins clockwise.  Again blades bite in, but this time it pushes the stern to starboard (pointing the bow to port).  My boat does the same thing. 
Title: Re: boat pulling to port when using motor!! Distress!
Post by: patrice on October 10, 2013, 06:47:46 AM
Hi,

Just to let you know that I have the same issue, but mine is a very easy fix.
It happen because I pull my dinghy attaching the line to the port cleat.
If I run the line thru the walk thru then to the cleat, it is a lot less pull, since line is more centered to the boat line.

I know sound funny, but I checked it by changing side, attach to starboard cleat, boat pull the other side.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: lazybone on October 10, 2013, 06:07:45 PM
I would never think it was impossible that lazy yard workers could have bent your rudder to one side or the other in order to remove and replace your new prop shaft.  Or they could have loosened the cutless strut and shifted that in order for the shaft replacement to clear the rudder.
They might have thought either of those was preferable to removing the rudder.

Good yard help is hard to find.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Roc on October 11, 2013, 03:55:31 AM
Based on what Kerk describes, it sounds like it's more than the usual prop walk.  Aldo made some good points about the yard being sloppy in their work.  If the boat is out of the water (or when it does come out), I would check to see if everything looks to be aligned (strut, shaft, etc.).  Also check the rudder, and put the wheel at the center mark and see if the rudder is also centered when you do that.  Maybe you think when the wheel is centered, your rudder is also, but maybe something has changed (cables?), so they don't line up anymore.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Indian Falls on October 11, 2013, 01:16:05 PM
Are you sure they put "your" prop back on?
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Ken Juul on October 11, 2013, 01:54:15 PM
The first season after I did the Ron Hill make your rudder eliptical mod I didn't get it quite right.  Had a similar pull to port.  The following spring I re-faired the rudder and the pull went away.  It really sounds like somehow the trailing edge of the rudder has been bent.  Goes along with what prh77 mentioned.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Clay Greene on October 11, 2013, 02:16:43 PM
I had the same thoughts as to both the rudder and the steering system but neither makes sense if the pull is occurring only under power and not under sail as well.  That's why I think it has to be something in the shaft-strut-propeller system that is causing the force applied under power to be significantly off-center. 
Title: Re: boat pulling to port when using motor!! Distress!
Post by: prh77 on October 14, 2013, 09:23:49 AM
I think the difference under power versus sail has to do with water flow over the rudder ie under power more flow. I also agree that a strut/shaft misalignment that would generate that kind of pull would also vibrate like hell. So I am still leaning twords a rudder issue.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Clay Greene on October 14, 2013, 10:15:52 AM
I would agree with you if you are comparing sailing at three knots to motoring at six knots.  But if the boat is sailing at six knots and not pulling to port but is doing so motoring at six knots, I think you have to look at the shaft and prop as the most likely causes. 

If the boat was pulling to port under sail, my first guess would be the steering system as that is more likely to be out of adjustment than major damage to the rudder or the rudder post. 
Title: Re: boat pulling to port when using motor!! Distress!
Post by: kerk fisher on October 26, 2013, 04:25:47 AM
Hi all.  I just got back from the boat which is 600 miles away.  Found something interesting.  The main tech person at the yard noticed that the shaft is coming through the shaft log very close to the starboard side, almost touching, way off center. Could this be the problem??? The strut is straight.  (All else looked good, prop is ours, rudder was new elliptical a few years ago) I looked at the cutlass bearing briefly and it looked good although it was only on the journey home that I wish I had looked more carefully to see if I could notice slight uneven wear. Would this shaft position provide enough of an angle so that the prop pushes the stern to starboard and the bow to port? I"m not sure why this would be so out of alignment.....  We didn't notice much vibration at all. Nothing out of the ordinary.  I've never done the alignment although it was done by another yard when the new shaft was put in. Will these techs be able to determine in the alignment process that the shaft is centered in the log even when the boat's in the water and cover by ( in the interior) by a PSS Packless sealing system.  I wanted to send a photo but nothing worked.(any hints on this process?)  Thanks, Kerk
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Ken Juul on October 26, 2013, 07:23:34 AM
Possibly.  But you really need to check the shaft alignment with the boat in the water.  The apparent misalignment may just be the way they have the boat supported by the jack stands.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Stu Jackson on October 26, 2013, 08:02:08 AM
Quote from: kerk fisher on October 26, 2013, 04:25:47 AMI wanted to send a photo but nothing worked.(any hints on this process?)

Kerk,

Posting Photos 101  http://c34.org/bbs/index.php/topic,3701.0.html (http://c34.org/bbs/index.php/topic,3701.0.html)
Title: Re: boat pulling to port when using motor!! Distress!
Post by: scotty on October 26, 2013, 08:43:36 AM
I re-read your post.  The problem is more than just a prop walk issue.  It showed up after you had a new shaft put in, so I would start there.  You should be able to fix this!!
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Ron Hill on October 26, 2013, 12:17:59 PM
Kirk : I've reread all of your posts and it sounds as though your problem has just started after the new stainless shaft was installed - is that correct??

If that is correct, it also sounds as though the yard must have changed the position of the shaft so it is now NOT centered in the middle of the molded tube that passes thru the hull which the PSS is attached to. 
I'll guess that the yard messed up that alignment installing the new stainless shaft thru the PSS dripless gland.  They did the work on land and never rechecked that alignment when the boat was back in the water. 
It is imperative to check final shaft alignment when the boat is back in the water for at least 24 hours with the rigging tuned.

A few thoughts
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Indian Falls on October 26, 2013, 06:08:40 PM
What RPM are you at when this happens?  Are you sure the tachometer is accurate?
Did they put the same prop back on that they took off?  Did they ruin your prop and then put one on that was laying around?  Your shaft misalignment will not pull your boat port or starboard, an 1/8'' of an inch over 5 feet means nothing to your problem with steerage.
Do you have the same prop walk to port when in reverse that you had all along before the shaft change?  I feel a lot of prop wash on my rudder through the wheel when I change direction and put the throttle up to 2000 rpm, but as soon as I get a few knots on the knot log that sensation goes away.  If I let go of the wheel and it's not locked the boat will careen right or left, but this is not a struggle if holding the wheel, nor is it a struggle to hold a straight course underway.  Hopefully all the experience available here will help you get to the bottom of this.   Good one...
Title: Re: boat pulling to port when using motor!! Distress!
Post by: kerk fisher on November 12, 2013, 07:34:03 AM
Again, thanks all for your continued interest in this mystery.  To clarify.  The problem began the second season after the new shaft and the pss was put in.  Maybe the alignment took a season to get out of wack?  Indian Falls thinks the alignment would not create the problem but maybe you, Ron, think it might.  Believe it or not we only backed one time this season because we only sailed for one week of anchoring due to an emergency abort mission to return home to an ailing mother-in-law so can't speak to the issue of prop wash while in reverse.

Three pix are included: 1. showing the shaft through the log.  2. The strut (what is the water stain?) 3.  The rudder. Clearance seems rather close at the top aft section of the rudder.  Note: bottom paint will be applied in the spring!

Title: Re: boat pulling to port when using motor!! Distress!
Post by: Jeff Tancock on November 12, 2013, 12:47:03 PM
That strut is looking very suspicious......
Grab it and give it a good push/pull from each side. It could be mush.
I discovered mine was shot when I was having some other work done last year. Electrolysis had destroyed it gradually over time.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Roc on November 13, 2013, 03:54:12 AM
The shaft coming out of the hull off center can be due to the fact that the boat is on stands.  The hull could be distorted.  On my boat, when on stands, some interior cabinet doors don't align as well as when the boat's in the water.
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Ron Hill on November 13, 2013, 02:24:34 PM
Kirk : Eyeballwise, The shaft should be coming out of the middle of the "hole in the hull".  Even on jack stands the bottom of the hull should not be warped that much.  If the yard knows what they are doing the jack-stands should be where there is a bulkhead and you should only experience side hull warp (the doors won't close right)!!

With the boat out of the water try this.  Remove the 4 bolts that couple the shaft to the transmission and then see how the shaft is - in or out of center.  Also shove the shaft (with prop attached) aft 5 or 6 inches and look at the wear pattern on the shaft from the cutless bearing (I assume that the strut is solidly secure?). 
Also move the shaft back in to place and it should easily mate back up at the transmission attaching points.

I still believe that your problem started and is caused by an improper installation of your stainless shaft.

A few thoughts
Title: Re: boat pulling to port when using motor!! Distress!
Post by: Indian Falls on November 23, 2013, 08:54:09 AM
Your prop looks like it has 3x the pitch mine does.  Could just be the angle the pic was taken. 
How about two  pics of your prop from the back and side? 

The angle of your ss shaft between the shaft log and the cutlass bearing being off 1/8'' is misaligned by only .23 degrees.   (If the shaft log is about 9 inches in total length and the shaft coupling is about 9'' from the stuffing box based on a 55'' long prop shaft and 1.25'' ID shaftlog.) 

You could misalign the the shaft to the other side and see if pulls to starboard....

Mine was misaligned this much (rub marks on the shaft from the log) and I noticed no "driveability" improvements after straightening everything out.