I have a puzzle that I am trying to solve and have had slight success but not to my satisfaction. When I am out sailing in my recently purchased NS 26 with the W21 there is an unidentifiable noise coming from either the prop shaft or the transmission. I can’t tell which one. When I reach a speed of about 5.5 kts. or so I hear a bump, bump, bump, bump,… noise coming from somewhere directly below the cockpit. When I haul the sails up and cut the engine I typically shift the transmission into neutral or if I forget it stays in fwd. Regardless of the gear, the shaft is freewheeling at a pretty good clip which I assume is normal. The noise seems to correlate to every revolution of the shaft. It used to begin it’s noise at a lower sailing speed (4 kts.) but since some investigating and attempts at correction it now is at a higher rpm. My first thought was that the connection from the transmission to the shaft was not secure and possibly the shaft had slipped back and the zinc on the shaft was making contact with the strut. When I checked it the setscrews were loose and so I went over the side and with a hammer and block of wood tried to tap it back in. It moved forward about 1/4" and the setscrews were tightened. The noise seemed to disappear. Now it’s back at the higher speed. But I now know that it wasn’t the zinc because there was a good 3/4" between that and the strut. Though I did notice a slight bit of play between the shaft and the strut. The cutlass may need to be replaced but the noise doesn’t sound like it’s coming from that. It’s too regular a beat.
When I am sailing and the noise is occurring I can put my hand on the inside bottom of the hull or on the outside of the transmission and can feel the vibration in both. I can’t tell which is stronger. I can’t tell if it is present when the engine is running as the noise and vibration of that would easily drown out the other noise. Everything seems to operate fine but this has been occurring since I first put the boat in the water so I don’t know if it is different from before. The previous owner says he remembers the noise at times but not that often and only when it’s really moving.
Is there something in the transmission or clutch that could be making that noise. The only way I can prevent the noise is to put the transmission in reverse which prevents the prop from rotating but that requires slowing the boat down to zero after raising the sail and that’s less than perfect.
Anyone else have this problem? I could live with the noise if I knew it was not anything that was going to cause some damage to anything. Any ideas or avenues of investigation would be appreciated.
Welcome to “the wonderful world of nonsuchery”.
By the fact that it stops when you have the transmission locked in reverse while sailing, would point you in a couple of directions - by the way, you should have no problem putting it in reverse while under sail without slowing down and it is preferred to keep it in reverse to save wear on the transmission clutches while sailing.
Since you said the shaft coupling set screws were loose and you could move the shaft tells me that the coupling to shaft fit may be worn - this should be a press fit and not easily moved. If that is so, you would have to determine why the wear - could be caused from misalignment of engine/ transmission to shaft. Could also be caused from bent shaft or very worn cutlass bearing. Worn cutlass bearings don’t make a lot of noise, but will also put strain on the P strut as will your prop coming in contact with the strut - strong probability for source of noise. You should have ample clearance between the prop and the P strut, around 2" works well.
Check to see that your P strut is secure as this can be a rhythmic noise source when the prop is rotating.
Quite a checklist but you should resolve it by checking those things.
Good Luck!!!
I will get into the habit of sailing with the transmission in reverse.
I have a fixed prop which I assume to be the original equipment. In my earlier examinations before the vessel was in the water and most recent while in the water, I could not find any play at all in the strut. It seems to be rock solid. No forward/backward play in the shaft or the prop. There’s at least 2" between the strut and the prop. There’s not much room between the shaft log and transmission to determine much but I can’t see anything that would indicate wear or anything loose other than the earlier mentioned fact that I could turn the set screws by hand. The shaft did not move easily into the transmission plate by tapping but took a pretty hard tap. I guess my next step is to separate the transmission plates and check for misalignment and possible bent shaft. After that I’m stumped. It must be in the transmission. I don’t have a real good understanding of the clutch but my assumpion is that it’s centrifugal that makes contact when the engine reaches a certain speed. That could be the source of the noise. I’ll have to see if there’s a detailed diagram in the owners manual.
ToddO
S/V Whisper NS26C #142
Wabasha MN
Again, thanks for the responses (Except you, e…@taxwiss. You’re not much help at all)
My recollection is that there isn’t a clutch per se but a drive plate that connects the trans and the flywheel. There is probably some type of syncro that slows down the tranny output shaft to effect shifting.
Disconnected the shaft from the transmission today and found no bend in the shaft and found alignment to be perfect. Shaft rotates easily while disconnected with no play at all and no sign of wear between shaft and flange. The flange on the transmission rotates easily also but I can’t turn it fast enough to try to duplicate what happens while sailing.
FYI the service manual states that sailing with the transmission in neutral will cause no detrimental damage to the transmission but should not be sailed while in forward and is possible to lock by using reverse gear. It doesn’t say what the effects are when sail in forward. Might be time to search out a Westerbeke mechanic.
I had a bump, bump, bump… noise when travelling at speed especially when a swell was running. In my case it turned out to be the upper bearing in the rudder shaft had worn. I got Mike Quill to make me a new bearing. All has been quiet since then. The old bearing had been in for 30 years. It is worth checking for play in the shaft in older 26s. The easiest way is to sail with the inspection cover off (the access port for the tiller) and observe for play.