1409RE: [j4x-owners-group] J42 Propeller shaft strut alignment
- Apr 9, 2014
The sea trial and the beginning of the passage where we noticed the vibration happened on the same river in the same conditions; flat with no wind. The vibration does not go away at higher rpm.
Between the broker, the surveyor and myself, someone would have noticed the vibration. It is not just annoying it is more like uh-oh.
I’ll check the alignment and the mounts. The later I can inspect visually for wear, etc. On the alignment, I have never done it and wonder if that is a DIY job?
It could be during your trial it was there but you just didn't notice it. During trials the speed varies and the trial usually doesn't last very long. A long passage under power on the other hand, in a calm river can show up all kinds of things. Odd noises, creaks etc. I'll bet the vibration was there all along. I know with our boat, often the first part of the season seems to bring more noticeable vibration, then I must get used to it and it seems to diminish.
As a test, motor in smooth calm water and then in rough water and maintain the same speed over the ground. See if the vibration changes. Your RPM with change under each different condition but keep the speed the same. If the vibration points or severity changes, it might be harmonic. If so you just have to find the sweet spot RPM. Like I said before, our vibration goes away at 3400 RPM, but no one want to motor full bore just to avoid vibration.
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On Apr 9, 2014, at 9:02 AM, "Barry Dwyer" <bdwyer@...> wrote:
Bill, I could almost accept the vibration if I didn’t experience it without any vibration during the trial.
Barry Dwyer, Partner
tel: 571.425.4780 cell: 571.236.4340
Vibration has plagued us ever since the boat was built in 1996. With our boat anything over 2400 RPM produces lots of noise and vibration. Some of it is harmonic as it goes away at full throttle. We have had a FlexOFold geared 2 blade folding prop which is a lot better than the Martec. ( I didn't like the Martec clunk which is normal or the fact sometimes a blade wouldn't open). I have just accepted it as fault of this particular model J/Boat. Some of the vibration is really water pounding on the underside of the hull from the prop. There is not a lot of blade tip clearance and water being thrown off the tips of the blades against a light hull seems to cause extra noise and vibration. Also it seems one sided. By that I mean rotation of the prop produces more noise on one side of center than the other.
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On Apr 9, 2014, at 8:22 AM, "Barry Dwyer" <bdwyer@...> wrote:
On this same topic, last October we purchased #53. During the sea trials the engine ran smooth and there was no vibration all the way to WOT. The boat had been on the hard for a year, was splashed for the sea trials, and then hauled again that afternoon. Again, no noticeable issue with vibration.
Fast forward two weeks and the boat is relaunched for the delivery down to Annapolis. Transiting the river down into the Gulf of Maine everything was fine until we went above 1800 RPM. At that point there was vibration that sounded like something on the prop. Backing down had no effect. As the boat was able to make 6.5 knots at 1800 we decided to continue the trip. There was one other factor; when you put the engine in forward there was a loud clunk associate with the prop opening. Not the normal Martec clunk but rather a cringing expensive sounding clunk.
So, put it in gear, loud clunk, 1000-1800 rpm all is well, 1800+ vibration.
This winter I sent the prop back to Martec. They said they had serviced it in the past and the pin was now the largest they could go but they did their best to recondition it.
Last week when I launched the clunk was less noticeable but I still had the vibration above 1800 rpm.
So my question is, could this be an engine alignment issue? Maybe something to do with being on the hard for a year?
Having just spent a lot of boat bucks I don’t want to buy a new prop if there is some other solution.
It's completely normal to have to realign the engine as its mounts compress over time. If the problem is the strut, it was either installed incorrectly in the first place (unlikely if you've put 1500 hrs on the engine), or it was hit.
This should be something you can judge for yourself. Just run something straight --- a broomstick, pipe, or even a piece of string --- from the engine, through the seal and strut. It should all be straight. A laser can also do the job.
On Tue, Apr 8, 2014 at 8:26 PM, William Stellin <wstellin@...> wrote:
Normally the alignment is done at the engine not the strut. The engine mounts all have bolts which can raise or lower each corner of the engine. I wouldn't touch the strut. It is glassed in and it would be huge job shimming it. Having said that, maybe it was hit and is bent out of alignment. In that case it would have to be fixed.
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On Apr 8, 2014, at 10:13 PM, johnrpotter@... wrote:
Hi all, after 1500 hrs on the engine, the cutlass bearing needed replacement. When we removed the prop shaft it had been badly galled and needed replacement as well. When we pressed in the new cutlass bearing, we found the prop shaft out of alignment with the shaft tube and transmission flange. The yard thinks I need to re - shim the strut.to bring it into alignment with the shaft tube and transmission flange. has anyone done this on a J42 or have any suggested options?
John Potter #57
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