Engine shuddering - Anyone heard of this?

[ontherocks83]

Originally Posted by JohnEasley

Oh Jeezum, I did.
This mechanic is a pretty good guy and doesn't seem to really be the type that would be offended.

That's good to hear Although I hope it is because he is humble and not because he "needs" the info (sorry i'm just a pessimist at heart and have found that typically the best mechanics are also the biggest jerks) (wait......they are also the one's that I end up being good friends with.)
Please do keep us informed on what ends up happening. I am curious to what the culprit is.

[MV Wanderlust]

Originally Posted by ontherocks83

Please do keep us informed on what ends up happening. I am curious to what the culprit is.

Will do.

[a64pilot]

Can you make it shudder?
As a mechanic myself I am fond of the expression I can't fix it , if it's not broken.
Seeing it shudder would go a LONG way towards being able to diagnose it, otherwise I'd just have to start checking likely possibilities and maybe waste a lot of time.

[MV Wanderlust]

Originally Posted by a64pilot

Can you make it shudder?
As a mechanic myself I am fond of the expression I can't fix it , if it's not broken.
Seeing it shudder would go a LONG way towards being able to diagnose it, otherwise I'd just have to start checking likely possibilities and maybe waste a lot of time.

Oh yes. It won't do it at all in neutral. Cast off, take it into some open water, and run it up to 1800 rpm... mild shuddering. Anything over 2000 rpm and it shudders much worse. The faster, the more shuddering. Consistently reproducible.

[Cadence]

Originally Posted by JohnEasley

Morning Bob,

Thanks for the suggestion. The mechanic who did the impellers is about a four hour drive where our boat's new home. He did the work and then we left out on a repositioning trip. I called him and gently discussed the situation. He said... and this is nearly a quote... "I don't want to tell you what I think it is because I don't want you to spend three or four thousand dollars if I'm wrong." He refused to say any more. Whatever. Not the first time he pulled that secretive thing. He's too far away to use him on a regular basis, anyway.

We have a local mechanic that we have come to trust. We have relayed all of the info from these posts and he's going to take a look.

That sounds like a lame excuse to dodge any responsibility. It didn't happen prior to his work. I would also think if he had suspected a problem, he would have mentioned it at the time of his work.

I hope it comes down to something simple.

[westwinds]

IMHO the motor mounts became potentially distorted with age and the loosening of the motor mounts to get to the water pumps caused the mounts to shift to a new position. I wound replace with all new motor mounts and align the engines again.

[Sailorbob8599]

Originally Posted by westwinds

IMHO the motor mounts became potentially distorted with age and the loosening of the motor mounts to get to the water pumps caused the mounts to shift to a new position. I wound replace with all new motor mounts and align the engines again.

Hi Westwinds, I do not agree with your suggestion because, although it sounds like a good course of action, basically what you are advocating is for John to become a "parts changer" which eventually is a very expensive way to troubleshoot the cause of a problem.
I believe John is doing the right thing by having a trained mechanic "troubleshoot" the cause of the problem and replace only those parts that are responsible for the cause. IF, after resolving the problem he chooses to replace all the mounts due to age, then that's his choice.
You might be shocked to learn the motor mounts on my engine are 35 years old and I have no problem with them so I do not agree the problem is necessarily "age" related. Also, I should add, my engine and its compartment are spotlessly clean. This may also have a bearing on an age related failure.

[Sailorbob8599]

Originally Posted by JohnEasley

Oh yes. It won't do it at all in neutral. Cast off, take it into some open water, and run it up to 1800 rpm... mild shuddering. Anything over 2000 rpm and it shudders much worse. The faster, the more shuddering. Consistently reproducible.

John, Just curious, why do you need to cast off & take her to open water? Would the problem not occur if you stay moored to the dock, put her in gear & run it to 1800+? ... I'm assuming you are moored to a substantial dock that will not move if you do this.

[MV Wanderlust]

Originally Posted by Sailorbob8599

John, Just curious, why do you need to cast off & take her to open water? Would the problem not occur if you stay moored to the dock, put her in gear & run it to 1800+? ... I'm assuming you are moored to a substantial dock that will not move if you do this.

We are moored to a substantial dock and it would do it if we stayed moored. I was just thinking about courtesy to my neighbors. I'm a thoughtful kind of guy that way. Besides, I like taking it out. But a mechanic is probably going to appreciate staying moored, if for no other reason than the time and convenience factor.

[Cadence]

Originally Posted by JohnEasley

We are moored to a substantial dock and it would do it if we stayed moored. I was just thinking about courtesy to my neighbors. I'm a thoughtful kind of guy that way. Besides, I like taking it out. But a mechanic is probably going to appreciate staying moored, if for no other reason than the time and convenience factor.

A mechanic will probably charge you for the cruise time. A good one will probably spot the problem with no more that looking at your mounts and if the last guy secured the engine back down. I wouldn't be an advocate of trying to take the dock for a cruise. JMHO

[MV Wanderlust]

Follow up: The props are balanced and back on. We took her out yesterday for about six hours. Turns out, all appears to be okay.

We had hired a captain to accompany us on the first day of our repositioning trip. On the first day, he turned on the Glendinning engine synchronizer, proclaimed it to not be working correctly, and shut it off. We never tried it again until yesterday. Turns out, it working just fine. We noticed the port tach on the dash appears to run slightly slower than the starboard tach when the synchronizer is on even though it sounds in syncs to the ear. On our repositioning trip, we were manually adjusting the throttle to where we thought they sounded in sync and we remember the port tach always showed even or slightly higher than the starboard. We believe that was why it was turning to starboard and the rudders had to be turned to port to compensate.

We also discovered only the most minor of engine shudder at 1800 rpm but above that it was steady as a rock at all other speeds. Woohoo! Appears the prop balancing may have done the trick after all.

Before leaving the dock, I checked all motor mount bolts and they were tight.

[donradcliffe]

Glad everything turned out OK. In retrospect, the first thing I do if I feel vibration is stop the boat and back down--many times its just weed or other trash on the prop.

[hellosailor]

"Before leaving the dock, I checked all motor mount bolts and they were tight. "
Funny, my torque wrench only has them Arabic Numbers on it, there's no setting marked "tight". For motor mounts, you might want to get some factory numbers and set them to it. Could make a big difference in the long term, fwiw.

[MV Wanderlust]

Originally Posted by hellosailor

"Before leaving the dock, I checked all motor mount bolts and they were tight. "
Funny, my torque wrench only has them Arabic Numbers on it, there's no setting marked "tight". For motor mounts, you might want to get some factory numbers and set them to it. Could make a big difference in the long term, fwiw.

My main concern was that the previous mechanic (in the original port, miles away) had left one of the nuts loose after changing the impellors. (this model of engine requires loosening the motor mount to jack up the engine to remove the water pump or access the impellor. poor design on a great engine.) A quick check proved that to not be the case. My new mechanic would be using a torque wrench labeled 'righty-tighty' and lefty-loosey.'

[tuffr2]

My torque wrench uses grunts...one grunt, two grunts, three grunts.

I like to measure with a micrometer, mark with chaulk, cut with an ax for precise work.

Cool you got it running smooth again. Good job

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