Noisy shaft when sailing after installing new engine and new seal

[De.windhoos]

Hi,
We just replaced our Yanmar 3GM30 with a brand-new 3YM30AE engine. during the install we also changed the volvo dripless seal and the cutless bearing.

We always have sailed with the transmission in Neutral (as advised by Yanmar) and have never had this problem. We have a Fixed prop.

Strange thing is that it only happens when under sail after a couple of hours when sailing at a nice speed (6+ kt). It does not happen under engine.

We are getting nowhere with the Yanmar Rep in Greece except switch to a folding prop (which we are not going to do).

I've linked a short video so you can hear the noise.
https://youtu.be/kmZIl6eQnlc

[roverhi]

If this is happening with transmission in neutral, would expect it's the prop being turned by waterflow past it under sail. Try putting the transmission in reverse the next time you hear the noise. Tried sailing with the Trans. in neutral on my boat with a 3GM30F. The noise generated by the freewheeling prop drove me crazy. Only lasted a few hours with the trans. in neutral on the first long passage. You had a dripless seal on the shaft which would seem to negate the sudden emergence of the noise coming from that. If you had had a conventional seal, the friction of the shaft packing might have stopped the shaft from turning before. Assume you have a fixed propellor which you didn't change with the engine swap.

Might buy an engine stethoscopes or just a length of small diameter PVC pipe and see if can hear where the noise is coming from. That's a tooth hurting whine much worse than the lower frequency rumble I had with my boat. Would think it's your shaft seal and hopefully will wear in before they commit you.

[Cheechako]

Maybe your old engine was out of align enough to keep it from turning. . Sounds obnoxious. It does sound like something is dry. Are yoyu sure your packing dripless is properly assembled? Shaft turning is a bit normal to me, as mentioned stop the prop turning.

[De.windhoos]

Originally Posted by roverhi

If this is happening with transmission in neutral, would expect it's the prop being turned by waterflow past it under sail. Try putting the transmission in reverse the next time you hear the noise. Tried sailing with the Trans. in neutral on my boat with a 3GM30F. The noise generated by the freewheeling prop drove me crazy. Only lasted a few hours with the trans. in neutral on the first long passage. You had a dripless seal on the shaft which would seem to negate the sudden emergence of the noise coming from that. If you had had a conventional seal, the friction of the shaft packing might have stopped the shaft from turning before. Assume you have a fixed propellor which you didn't change with the engine swap.

Ok. I know a lot of people sail with their transmission in reverse, however Yanmar specifically states that this should not be done and will void the warranty on the gearbox.
We didn't change the prop and have always sailed in neutral without any weird noises.

[sandy stone]

Did you grease the Volvo shaft seal?

[s/v Moondancer]

I have a hydraulic transmission. Instead of a folding prop I just use a large vice grip on the prop shaft as a prop brake...worked fine for the last 30,000nm under sail.

I leave a red flag on the ignition key to remind myself to remove the clamp before starting the engine.

The problem with letting a transmission spin when the engine is not running is that there is no transmission oil cooling and you are letting a mechanical system turn needlessly.

[Cheechako]

You havent mentioned if the shaft spun before? it's key. If it spun before with no squealing, then you may have an assembly, or at least a lubrication issue. I dont know your seal type, does water cool it? Or if it spun before with no squealing, then maybe you are out of alignment now.

[De.windhoos]

Originally Posted by Cheechako

You havent mentioned if the shaft spun before? it's key. If it spun before with no squealing, then you may have an assembly, or at least a lubrication issue. I dont know your seal type, does water cool it? Or if it spun before with no squealing, then maybe you are out of alignment now.

Yes, it spun before in neutral with the old engine without the squealing.
The seal is a Volvo Penta dripless seal that is water lubricated.

Ok I'll check the alignment, but wouldn't I have the same noice with the engine under load?

[roverhi]

The alignment would have to be so far out to bind up the shaft and make that squeal that it would be detectable by eyeballing. Is there a water relief port with a hose on the dripless seal?? If that is missing there may not be a way to relieve pressure inside the seal so water can migrate in and lubricate it. Was this Volvo Seal new or a carry over from the old engune?? Knowing the price of genuine Volvo parts wonder why you went with that rather than LasDrop or other seal.

Know what Yanmar says but the sound of a spinning prop drives me nuts. I'll pay for a rebuild rather than listen to that for 15 sraight days and mine wasn't nearly as annoying as yours..

[sandy stone]

Note that Volvo shaft seals must be greased annually, and I assume on initial installation. The way I do it is to get a large-diameter soda straw, like you might get at McDonalds, and force waterproof grease into it by stabbing it into the grease container. Then you pinch the end flat and work it between the shaft and the seal, in about 1/2 inch or so, and push the grease into the seal like you were pushing toothpaste out of the tube. If you do this, your noise might go away, and the life of your seal increased.
My Volvo seal has been drip-free the 6 years I have owned this boat, who knows how long before that, and I consider it to be much simpler and less likely to fail catastrophically than a face-type seal.

[Wotname]

Originally Posted by De.windhoos

......

Ok I'll check the alignment, but wouldn't I have the same noice with the engine under load?

Possibly yes, possibly no.

However with these unusual problems there are two ways to attack the issue. One way is to try random ideas that may or may not be the root cause and the other way is to analyse the issue and do more investigative work to determine the cause. I prefer the second way .

From what you have posted, the issue began after:

1. New engine fitted
2. New dripless seal fitted
3. Only occurs while sailing with the stern gear free to rotate (i.e. in neutral with engine off)
4. Only occurs after a few hours of sailing at around 6 knots (or presumably more?)
5. The noise (from the video) varies in pitch with the speed of shaft rotation.

First in analysis would suggest it has something to do with the new seal or prop alignment. But it could be coming from the new gearbox however this seems unlikely to me.

So why does it only occur after a few hours of sailing, why not after a minute or so. This suggests something changes after a few hours - probably something to do with the seal but perhaps something with the gearbox.

To try to pinpoint it more, I would try the following.

1. When the noise next occurs, start the engine and motor sail for say 5 or 10 minutes. Does the noise reoccur almost as soon as you stop the engine or does it take a few more hours before it comes back.

2. When the noise next occurs, stop the prop from rotating for say 10 minutes by either popping it into reverse or by some other method of locking the shaft. 10 mins with prop locked is hardly going to upset the gearbox. Does the noise reoccur almost as soon as you let the shaft rotate again or does it take a few more hours before the noise reoccurs?

The answers to the above might help in pointing you to either the root cause or point towards other diagnostic actions.

[sailstoo]

Same thing happpens on my Yanmar 3DMD...even though I have a folding two-blade prop, Puit it in Reverse. No more rotation. No more noise. No more wear.

[Captsteve53]

Alignment Required and needs to be with in a few thou! , under load from the engine the noise is not there due to the force/load being applied to the bearing, free wheeling presents no real load and thus the squealing.

There are some very nice auto type lock/unlock shaft locks out there today as well, I know Yanmar state to leave in Neutral for the reason if in reverse the vibrations can cause the gears to bind (requiring flicking the starter in forward to release-all to hard!), I cant imagine how ever sailing any distance with a free wheeling prop no matter how the noise!!

[boeing1]

I think I would first check the shaft alignment

[Cheechako]

Originally Posted by De.windhoos

Yes, it spun before in neutral with the old engine without the squealing.
The seal is a Volvo Penta dripless seal that is water lubricated.

Ok I'll check the alignment, but wouldn't I have the same noice with the engine under load?

I would likely check alignment first, although, I've had boats pretty far out and no issues like that squealing.... but I dont let props free wheel usually. It is time to check the alignment after the new engine installation anyway if you havent. Was it aligned in the water?
Under power the shaft is trying to push the engine forward, under drag the shaft is trying to go back out of the boat. I wonder what is in your system that makes a difference? Any thrust bearings/washers in that volvo dripless seal?
Maybe it is the transmission... could be a bearing in there. It starts after some time not right away? Sounds like a heat issue to me and something not lubricated. Is the seal assembly getting cooled? lubed?
Have you felt the shaft after doing this for an hour or two? is it hot?

If it were me I would be hauling the boat and removing the shaft and seal and inspecting all.