Bad Vibrations

[Bill1565]

My boat had bad vibrations when I bought it. In gear and out, at all rpm. You could reach out with a boathook, grab the shaft and end the vibration. So I bought it

Boat had an old wobbly Martec folding prop and a post hurricane replacement strut. Replaced the shaft, remounted the strut, replaced the Martec with a 3 blade Campbell sailor that came with the boat. Lined it all up. Vibration out of gear went away, only vibrated in gear at 2000-2500 rpm. That forced me to chose between 4 knots at 1800 and 6.5, near WOT. Could stop vibration by placing my foot on the engine block and pushing. Guessed that rear motor mounts were bad.

Had the two rear motor mounts replaced as I could neither see them nor fold my body enuff to work by feel. Re aligned shaft. Motor is now rock steady, shaft vibrates in shaft log in neutral and in fwd at all rpm.

Got a diver lined up to pull the prop, gonna send it out and check for balance and pitch. In a week or so tides will allow access to my DIY boatyard.

Anybody out there have experience with the thrust bearings that you mount to the hull? Anybody replace a PSS dripless with traditional rubber tube/packing gland?

 

[John Nantz]

A real Hands-on sailor!

Pun intended. Can't answer your two questions but I have a comment about the shaft setup.

One thing one might try is checking the flange on the back of the transmission for trueness with the output shaft. Say, set up a dial indicator so that it rubs on the outer edge of the flange and with the engine vacuum breaks open spin the engine with the starter and note any variation on the dial. The deltas would indicate if the flange is really faced 90 degrees true to the shaft.

If that is okay, then pull the prop shaft and take it with the flange to a machine shop and have them check the shaft for trueness and do the same thing with the flange on it as above.

If either of the two flanges are not 90-degrees true to the rotation axis it will cause a problem.

Having the prop balanced and pitch equalized like you're doing should help eliminate that item as a question, too.

 

[redhead78]

I don,t think it has anything to do with your problem, I replaced a PSS dripless with a new buck algonquin stuffing box, I feel safer with the stuffing box. My pss dripless was ok, but when it let go it was a big leak. Red

 

[Bill1565]

I don't suspect the PSS dripless of being the problem. I am thinking that a traditional rubber hose/stuffing box will dampen shaft vibration better.

Got over being bummed out, gonna mess with boat today, maybe video the vibration dockside. Diver is coming next week to pull prop (water is reported at 55. Ttoo cold for these old bones.)

 

[Mike B]

I had a motor mount crack on the previous boat. Had the mount replaced under warranty (by a local marina not the dealer)but they never realigned the engine/shaft. They also overtorqued one of the mounting bolts weakening it to a point that it eventually broke. At that point I did the repair and alignment myself. A tedious process to say the least. If it were me I'd redo the alignment again. Anytime you make a change and it makes it worse it's time to back up and redo the adjustment/change. If you haven't done so already check the play in the cutlass bearing. If it's worn you won't be able to align the prop shaft correctly. Also check to make sure that when the coupling at the transmission is disconnected the prop shaft doesn't drop or have any flex. If it does, even by a minute amount, the alignment you perform will be off. Best to support the shaft with a block when doing the procedure. Start with the easy stuff first. Keep notes on all changes/adjustment should you need to go backwards. Good luck.

 

[RichH]

Before you engage the diver, Suggest you disconnect the shaft to transmission coupling and ascertain if this isnt an 'engine dynamic balance' problem. You posted that "In gear and out, at all rpm"; and, if thats accurate would eliminate/exclude prop imbalance, shaft whip, engine alignment, etc.

 

[Bill1565]

Oh, I hope not. I'm in the boondocks here. I'd probably have to have the engine pulled and sent to Miami. It's a Westerbeke 35D with way less than 100 hours and before the new motor mounts the only problem was at cruising rpm in forward. smooth, but

 

[Ed Schenck]

I'm with Rich, sounds like engine and not the drivetrain. You had the rear mounts replaced? And that was a good installation? Sometimes the mounts can be good but they don't secure well to the rails. A 3-cyl will vibrate a little so maybe its normal. Or is it really shaking? My 3YM30 has one low RPM range where it "rattles" a little in neutral. With new shaft, 3-blade Flex-O-Fold, and new cutlass bearing my drivetrain is rock solid(standard stuffing box). But my shaft saver probably has a lot to do with that.

 

[Bill1565]

Well the admiral is committed to fixing it whatever it is. We aborted a short cruise yesterday when the wind died and limped home at 1500 rpm to keep the rattle down.

I opened up the boat, but it is hopeless. I'd' have to crouch in the starboard locker and work blind with my hands below my feet. Alternatively, I could work left handed only, lying on my right side in the quarterberth. At 240# 70 yrs old with a bad shoulder from rewiring, neither is gonna get me where I need to be..

Last hired gun was highly recommended. Put in two rear motor mounts, replaced two lag bolts in front. Said he lined it up. Gonna hire another one and watch him closely.

 

[Witzend]

Is it possible that you have lost some of the springs from your damper plate? That would cause an imbalance in the system.
Along with the vibrations, at idle do you hear some rattling sounds, (sounds like marbles rolling around in a coffee can, not to be confused with shaft slap)? Again, disconnect the drive shaft from the coupling to isolate.

 

[Bill1565]

Anything is possible. Gonna go at it again tomorrow. Can ge left hand in there to check for stripped lag bolts, loose motor mount nuts. May be able to get admiral in
stbd locker to hold nuts, while I loosen bolts. Thans all of you for your inputs. I'm stumped.

 

[Ed Schenck]

If you have problems working through those two openings then not much chance of getting the shaft loose I guess. But I agree with Witz on that score. Not sure what you mean by ". . to hold nuts, while I loosen bolts." Where are the bolts that have to be "held"?

 

[woodster]

i dont remember seeing any one mention a fowled prop or maybe even a bent one...just a suggestion ........

regards

woody

 

[Bill1565]

Not sure what you mean by ". . to hold nuts, while I loosen bolts." Where are the bolts that have to be "held"?

Will make another run at coupling if we can. It's only 4 bolts. If the admiral can hold , I can maybe loosen with a ratchet left handed from the QB.

 

[Bill1565]

Thanks Woodster. One thing we have here in rural SW Fl. is divers to clean foul bottoms. Mine is looking for his prop puller even as we speak. Easy, quick and cheap. maybe it will even work.

 

[redhead78]

Duff, I am sorry I did not mean I had a bad experience with a Drippless device. I had one come on the boat and was good for 8 years without doing anything to it. Finally it was leaking pretty badly probably due partially to ignoring it, but mostly from vibrations form a completely bad drive train, engine mounts, engine also.What I meant was beig I was changing every single component in my engine trans system, I went back to a traditional stuffing box with flax packing. I think it gives me more options for repair. SO I would not worry if you just had a dripples installed, Its more of a matter of preference...... Red

 

[Bill1565]

mean by ". . to hold nuts, while I loosen bolts." Where are the bolts that have to be "held"?

My coupling has 4 bots and nuts holing it to a shock absorber pad, beige, not hot orange like yours,

 

[RichH]

Bill1565-
Question - what is the amount of 'vibration' with the engine's transmission in NEUTRAL and the with the engine brought up through the entire range of operating rpm: idle rpm through 'cruising rpm' .... while in NEUTRAL?????

 

[Bill1565]

Lots of shaking maybe +-1" below about 1200 rpm on the tach. up to 1/2" from there on up.

BTW I think we've got it beaten After replacing the stripped bolt in the forward motor mount, a friend who I asked for suggestions, noticed that the motor mount and the motor foot were almost touching the bulkhead between the engine room and the QB in front of the fuel tank. When I stuffed a paint stir stick (about 1/8 x2 ) in the gap while the motor was vibrating, the rapping ceased. We checked and secured all the little pieces separating the quarter berth from the engine, replace the stir stick with some hard rubber hatch seal that I had and it sounds great at the dock. Not what I'd call an elegant solution, but at least the admiral will go out on the boat with me.

Main Sail's snowball effect works here in florida, and the PSS seal is spraying water out. I can't reach it and the admiral can't move the SS ring so sea trial will await the arrival of a small strong person.

Friend with a H passage 42 told me he had to replace the front motor mount with a
different one as he could not get his water pump off. I will look into this for a summer project and more permanent fix.

 

[redhead78]

Do all hunters have a single front engine mount? When I was repowering my boat last year I was thinking engine compartment was small and mounts were hard to get at, not so much after looking at a lot of your pics. Red