Shaft vibration

Post here if you want to discuss a topic specific to the MV/32, MV/34, and MV/41.
User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Shaft vibration

Postby Captnautigal » Fri Nov 18, 2011 9:02 am

We recently had leaky shaft seals. I had some knowledgeable mechanics, recommended by Tides Marine, come out to the boat. They repositioned the seals and stopped our leak. We told them that we learned there’s been issues with several PDQ’s engine alignments causing too much vibration and resulting in leaky seals. They checked engine alignments on both engines; both were in proper alignment. They did notice that when they turned the shafts by the coupling on the back of the engine that vibration resonated through the boat on ¼ of each turn. I was in the boat when they were working on it. I heard it loud and clear! This happens on both engines. They undid the coupling and tried turning the shafts in a slightly higher position then a slightly lower. There was less vibration when in the lower position. The noise seems to be coming from the top of the stern tube. Is this vibration common to all PDQ power cats? If you turn your shaft can you hear or feel any vibration. Shouldn’t it be silent and smooth??? The shaft turns very easy. The props and bottom are clean. Our cutlass bearings were replaced March 2010 with only a few hundred hours on them since installed.
Maureen (Captnautigal) and David
Catatonic - #74

duetto
admiral
admiral
Posts: 592
Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: Shaft vibration

Postby duetto » Fri Nov 18, 2011 12:19 pm

hi,

i am not familiar with anything remotely resembling what you describe. when you describe a "vibration" i'm not sure what you mean? you're getting a "vibration" when you're rotating the shaft by hand? did you measure to see if shaft is fairly centered in the stern tube? is it a rubbing as opposed to a vibration?
john & diane cummings
duetto mv34 #23

James Power
admiral
admiral
Posts: 192
Joined: Tue Apr 01, 2008 3:30 pm
Location: Georgian Bay

Re: Shaft vibration

Postby James Power » Fri Nov 18, 2011 6:51 pm

Hey Captnautigal,

Some times you can get a squeak out of a cutlass bearing. If it's that loud, might want to haul the boat and check things out.

James

User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Re: Shaft vibration

Postby Captnautigal » Fri Nov 18, 2011 8:29 pm

Definelty not a squeak. More like pushing a heavy piece of furniture across a hard floor! It only does it on 1/4 of the turn (manually by hand - the boat is in the water). It is loud enough that I could hear it loud and clear sitting in the salon. If you put a cell phone in the engine compartment you can hear it over the phone. Not sure if the shaft is centered in the stern tube. Isn't that view blocked by the Tide seal boot? (I have red by the way). There is water flow to both seals. Strange thing is, it does it on both engines. We're off the boat for the next two weeks but plan on running her hard after having the tide seals repositioned and the engine aligments checked. It is my understanding that for accurate engine alignment the boat must be in the water since flexing of boats on the hard will affect the alignment. If it still makes this noise after we run her, we plan on hauling her to see if the cutless bearing have slipped. Maybe the boat always made this noise. You'd never hear it with the mattresses in place and the engines running. Is it a normal noise to these boats? I have twenty plus years experience on larger power boats. The mechanics that I had on the boat never heard anything like it. That's why we thought we'd thow this out on the forum and see what responses we'd get. We were due to come out this spring anyway. Just hate to not have the boat over the holidays.
Maureen (Captnautigal) and David
Catatonic - #74

Mary & Roger
admiral
admiral
Posts: 105
Joined: Wed Mar 26, 2008 2:52 pm

Re: Shaft vibration

Postby Mary & Roger » Sat Nov 19, 2011 9:31 am

Teamwork has a squeal on the stbd side between 1200rpm, and 1800 rpm. Had a mechanic tell me that it was the cutlass, not the transmisson. Mine are new, and he didn't think it was a big deal, some sing, and some don't. I don't like the noise, so I pull stbd engine to idle and continue thru the no wake/mamatee zone on the port engine. No noise at 2800 rpm Roger Comer

duetto
admiral
admiral
Posts: 592
Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: Shaft vibration

Postby duetto » Sat Nov 19, 2011 10:56 am

hi,

after re-reading the original note, the sound also comes with the shaft disconnected from the coupling, so this isn't the harmonic squeal that roger is talking about. the stern tubes are made out of some ceramic like material. it's not like any fiberglas that i'm used to. i can tell you that when scraped it makes a sound like fingernails on a blackboard. so that maybe the sound but what is scraping? the shaft would have to articulate to a bizarre angle to rub against the tube. the only things that should be touching the stern tube are 1) the tides seal boot 2) the cutlass bearing. possible that the cutlasses are loose, i admit not likely. how about a line cutter rubbing on the end of the tube?

good luck, and let us know what you find out.
john & diane cummings

duetto mv34 #23

User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Re: Shaft vibration

Postby Captnautigal » Sat Nov 19, 2011 11:27 am

Thanks for getting back to me. I did have line cutters installed (the razor kind that look like little saw blades) when we bought the boat. I've been running with them for almost two years. Do you think they may be mounted too close to the tube? I've looked for photos of my gear when out of the water. I don't have any photos after the cutters were intalled. I had them installed at Stuart Marine. I've dove on the gear before and don't remember anything unusual. Anything in particular to look for? I have a diver once a month. I have had the boat in areas with severe crustacean growth on the gear. I've even tried speed prop with no great results. Do you suppose I can have growth between the blades and tube. We had a terrible grinding noise about a month ago after the boat sat for four weeks. It cleared up after bumping in and out of gear in the slip. (suggested by my Yanmar Mechanic). We then took her out. That's when I noticed the seals starting to drip and all this madness started! I'm very anxious to give the boat a good run. I must admit, when I first heard the sounds I was afraid to run it. I thought it sounded expensive!!!! Possibly a tranmission problem. I had the boat sit for weeks before, in all degrees of salinity including the Bahamas. This is her first summer in Miami. Perviously she was berthed in North Florida when not cruising. I appreciate everyones input. When we get to the bottom of this I will post results. My diver said the gear is all clean - maybe he can't get between the blades and the tube??? I'll ask next time he's out to clean her.
Maureen (Captnautigal) and David
Catatonic - #74

duetto
admiral
admiral
Posts: 592
Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: Shaft vibration

Postby duetto » Sat Nov 19, 2011 11:36 am

just saw your post. i think diver would notice that kind of buildup near stern tubes.
john & diane cummings

duetto mv34 #23

User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Re: Shaft vibration

Postby Captnautigal » Mon Dec 19, 2011 7:57 pm

Ok, Got back to the boat climbed behind the engines and turned the shafts by hand. Definitely made a course abrasive sound which carries through the boat. Took the boat out and ran her for a few hours. When we got back climbed down behind the engines turned the shaft by hand. No abrasive sound - just the minor squeek of the shaft turning in the rubber cutlass bearing - barely audible. The salinity must be such in our new marina that we get a build up of salt between the shaft and cutlass bearing which makes the terrible noise before running. As I mentioned before, we had the shaft alignment checked and it was OK. We had the red dripless Tides Marine shaft seal repostioned at this time since they started dripping around the same time. I wiped all wet salted areas clean with salt away. While running the boat I didn't notice the seal leaking but a small amount of water accululated aft under the seals. Not enough for the bilge pump to clear our. Maybe this was water sitting under the engines that flowed aft once under way. I wiped it all clean again and will inspect on next running of the boat. I have to admit 20 years of boating with conventional shaft log packing was a lot less trouble then these finicky dripless seals. Granted the bilge was wet but I never worried about flooding!
Maureen (Captnautigal) and David
Catatonic - #74

User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Re: Shaft vibration

Postby Captnautigal » Wed Mar 21, 2012 10:42 am

Wanted to post this follow up. I also posted in on the Bent Shaft topic since it applies there as well:


Catatonic is back in the water. Stuart Yacht did a great job with our shafts. We had them removed from the boat. They were sent to the shop to be examined and ultimately straightened and recondidtioned. Much care was used in reinstalling the shafts making sure everything was in proper alignment. The cutlass bearings were changed and they also added half bearings in the forward portion of the stern tube. They measured the length of the shafts and this additional support is half way to the engine coupling. This helped keep the shaft aligned as it came through the tube to the back of the engine. We also installed new red Tide Seals. Dave Mayo from Tides Marine and Gregg Burdick, Stuart Yacht, talked at length about the PDQ shaft issues. Both are excited to see if the second bearing will assist in keeping the shaft aligned and stop the bending, which, my understanding, is a result of the whipping action under the current configuration. We also plan on installing aqua drives on our next haul out. We ran the boat on and offshore to the Keys from Stuart. She was noticably smoother - especially at idle speeds. The work we have done at Stuart Yacht is always exeptional and first rate. It's great meeting all the other PDQ owners that are being serviced there as well! Already starting our wish list for our next visit!!!
Maureen (Captnautigal) and David
Catatonic - #74

duetto
admiral
admiral
Posts: 592
Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: Shaft vibration

Postby duetto » Mon Mar 26, 2012 4:29 pm

hi dave,

you say you added "half cutlass bearings". is it half length? if so, why didn't you use a full cutlass bearing?
john & diane cummings

duetto mv34 #23

User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Re: Shaft vibration

Postby Captnautigal » Mon Mar 26, 2012 6:29 pm

John,

Its Maureen not David. I'm captnautigal!!! We are a not your ordinary cruising couple. I've been captaining boats for about twenty years. Even have my Masters. My experience is extensive in the Bahamas, I ran a boat from Nova Scotia back to the states and crewed a bit in Alaska. Can't count the number of times up and down the ICW over the years. I do most of the minor maintanence myself. We always joke and tell people David is in charge of the mating on the boat, since he is not very mechanical, and they keep asking him questions!!! ;)

With that said, following is an explanation regarding the half bearings from Gregg Burdick. When we started having the vibration/leaking seal issues, I knew Stuart Yacht was the place to go to get to the bottom of this. I have complete confidence in Gregg and his team. Their thorough knowledge all boats, including PDQ's is impressive. We wouldn't consider another yard!

From Gregg:

With the full bearing at the propeller end of the shaft, and the support of
the gearbox coupling at the front end of the shaft, a half bearing is all
that is needed. A full bearing would be ok, but not necessary. This all
changes for other vessels/ shaft size, etc. The calculation is based on
shaft size and alloy, engine HP, and gear box ratio. A shaft should be
supported along its length as dictated by such a formula, although the
formula was not needed in this instance as there were not good options, and
the position of the half bearing just happens to be roughly at the halfway
point on the shaft.

The ID of the bearing is the same as the shaft (naturally). The OD of the
shell is less due to the tube dimension. Easier to use a lesser OD than to
machine the tube.

Gregg Burdick STUART YACHT 450 SW Salerno Road, Stuart, FL 34997 772
286-9800 Gregg@StuartYacht.com
Maureen (Captnautigal) and David
Catatonic - #74

duetto
admiral
admiral
Posts: 592
Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: Shaft vibration

Postby duetto » Mon Mar 26, 2012 7:52 pm

maureen,

that's what's so hard when people put the couples name on the post. i assumed, and yes i know what that means, and i apologize. if we ever meet up i owe you a cool one of your choice.

now the questions just start coming. what holds the cutlass to the inside of the stern tube? did you change the motor mounts?

i would ask that you promise to report in regularly on the results of your change.

three of us were at a bar here in abacos today hypothesizing on what you did and what will happen.

keep us posted.
john & diane cummings

duetto mv34 #23

User avatar
Captnautigal
1st mate
1st mate
Posts: 39
Joined: Mon Jan 25, 2010 8:32 am
Location: Miami Beach, FL

Re: Shaft vibration

Postby Captnautigal » Mon Mar 26, 2012 10:06 pm

Mark told me he had to use a slightly smaller OD bearing since the forward portion of the stern tube was not machined. I think he used 5200 or epoxy. The tubes and seals look the same as before the change. I was concerned the bearings would never come out again after using 5200. He said they will be able to get them out if they needed changing. I can tell you this, the ride is much smoother at lower rpms. At idle speeds, our dishes used to rattle on the shelves! It was not from the idle being set too low!!! We did take the boat down to the keyes for a few days after picking her up from Stuart. We are back in South Beach now and may go back to the keyes towards the end of April, so we will be putting miles under her. After long runs, I would open the engine hatches and inspect for water. (In the beginning we ran with them open and frequently checked for leaking) I will keep you posted if anything changes. I really felt something needed to be done since there was such a history of failing shaft seals and the boat in the yard before us also had bent shafts. I was surprised that on haul out our two year old bearings were worn so unevenly. I did have engine alignment done in the water and that checked out fine, after Dick first recommended we do this. I spoke with Dave Mayo, Tides Marine, on several different occasions. I asked about 4 bladed props - he said that was more for preformance not vibration. He suggested checking the motor mounts. He felt vibration was contributing to the premature seal failures. Our mounts were fine. We were willing to change them out if they were suspect. I was leaning toward aqua drives; but Stuart Yacht felt this less expensive alternative would resolve the whipping issue. I know they took great care in making sure the shafts went through the tubes to the coupling aligned straight!! So far - we are happy. I know if you have any questions, Gregg or Mark would be happy to discuss this with you. Have a drink (or two) at the Jib Room for me. Tell Boo, Tom, Jason and Stephen I said hi!!! Not sure if we will be over this summer.
Maureen (Captnautigal) and David
Catatonic - #74

duetto
admiral
admiral
Posts: 592
Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: Shaft vibration

Postby duetto » Sun Apr 29, 2012 3:21 pm

maureen,

any interim observations/results?
john & diane cummings

duetto mv34 #23


Return to “PDQ Powercat Forum”

Who is online

Users browsing this forum: No registered users and 1 guest