Big Vibration with New Engine ?

[sailvayu]

It is possible the mounts are too soft. Even new mounts of the wrong type can allow the engine to get into a harmonic oscillation really shaking the boat. I think more information is needed to figure it out but I would agree with the other posters and hold the money till the yard figures it out and makes it right. My experience dealing with Volvo is they are never wrong even as the engine is melting down and smoke and sparks are coming from it they refuse to admit it is anything wrong with THEIR motor! (I swear they said that on a new boat sea trial as the engine flew apart! They did give the guy a new motor in the end lol)

[Reefmagnet]

Shot in the dark - resonance?

Edit: sailvayu beat me to it so what he said

[MarkSF]

Originally Posted by cburger

Misallignment issue, tranny to shaft coupling needs to be within .005 thousands of an inch and can be a very painstaking process that requires considerable time and patience to get right. Motor mounts should be changed out as GP as part of the repower. Run the motor at in gear at the slip and grab the shaft with your hand and you will feel distinct wobble if there is a problem with adjustment. I don't understand the term agent but who ever did the work should not be paid until the job is made right. The other issue is you don't want to run the motor like this to long as you can damage the tranny.

How would a misaligned tranny to prop shaft coupling result in vibration out of gear? It won't. Misaligned engine to gearbox might.

Won't grabbing the shaft with your hand while it's turning be both painful and possibly crippling?

[Tellie]

It's very likely the issue that is making it shake out of gear is still there when it is in gear just not noticable because the trans is firming the engine as it backs the torque against the trans. While it's impossible to diagnose over the Internet I'd suspect bad motor mount set up.

[MarkSF]

Originally Posted by Eleebana

A friend of mine has just repowered his Beneteau 34.5 with a new 30 hp Volvo engine, done by the Volvo agent at Lake Macquarie. The engine is the same size as the previous Volvo and is of the model recommended by the agent. He has paid for the engine but not the labour for the fitting of it. The driveline has a massive vibration and is jumping all over the place when it is in neutral but when he selects forward or reverse it settles down and is quite normal. The agent has suggested he take it (& pay for it) because it should settle down after about 20 hours. He and I think not. It has had new mounts and the agent can't find the problem.

Does anyone have any ideas what might be the problem?

Greg

Unless the agent can suggest a convincing mechanism whereby a vibrating engine will get better after 20 hours, I would take it with a pinch of salt. Sounds like the kind of thing a less scrupulous car salesman would say.

[S/V Antares]

Does the vibration clear as you ease up the throttle? If so you really need to use a photo tach or hand held mechanical one to set the correct Idle and while at it correct the panel tachometer.

[Chief Engineer]

Idle set too low
Misfiring Cylinder(s)
Wrong motor mounts

[Sabbatical II]

Well here's the answer.

The Volvo dealer upped the idle speed by 50 RPM this morning and the problem has gone. The owner did tell me that they set it at 850 RPM which was factory specification. However they've had to set it at 900 RPM so maybe the motor is a bit tight or whatever. I'm still amazed that the authorised Volvo dealer wants you to drive away when they know it's not right and all for a simple adjustment. I also let my friend know that if he joins CF he can have all this wisdom for free. Thanks everybody.

Greg

[svBeBe]

Originally Posted by Eleebana

The driveline has a massive vibration and is jumping all over the place when it is in neutral but when he selects forward or reverse it settles down and is quite normal.

Does anyone have any ideas what might be the problem?

Greg,

All diesel engines that I have seen vibrate at idle and then smooth out with a change in RPM, or a change in load. "Massive" is not really quantitative and there is no way for anyone to legitimately help you with your question, other than to advise your friend that if he feels something is wrong to seek a second opinion from an expert diesel mechanic.

Hope this helps,

Bill

[pillum]

Quote:

Originally Posted by svBeBe
You guys are way too funny.

Do you think that CF is the only place to meet "experts?"

10 years ago there were other places, as there are other places today.

And, yes, 10 years ago, like I said in my original post, I was convinced the advice I got on a similar forum/group was genuine. It was not!

I hope that some of the virgins reading this thread will learn something from what I have said...but be careful virgins because I could be the person misinforming!

Bill
End quote

Sounds like it could be a costly problem, probably a good idea to pay an expert to look at it, rather than solicit input from a free forum.

Paul

[cburger]

Originally Posted by MarkSF

How would a misaligned tranny to prop shaft coupling result in vibration out of gear? It won't. Misaligned engine to gearbox might.

Sorry, I missed the "Neutral" in the post.

Won't grabbing the shaft with your hand while it's turning be both painful and possibly crippling?

No, just did this last week as a final check to confirm allignment on a new installation after the boat was cruised under load, your hand will be very sensitive to potential problems. Maybe grab was the wrong word, more like grasp.

[atoll]

Originally Posted by cburger

No, just did this last week as a final check to confirm allignment on a new installation after the boat was cruised under load, your hand will be very sensitive to potential problems. Maybe grab was the wrong word, more like grasp.

don,t try this if wearing a neck tie..........

[sdowney717]

Misallignment issue, tranny to shaft coupling needs to be within .005 thousands of an inch

he says it is jumping around in neutral, so this coupling wont be spinning

[Therapy]

Sounds like it could be a costly problem, probably a good idea to pay an expert to look at it, rather than solicit input from a free forum.

Paul
[/QUOTE]

My experience here is that there a lot of experts that help (for free) and that is as good or better than one paid "expert".

[pillum]

Originally Posted by Therapy

Sounds like it could be a costly problem, probably a good idea to pay an expert to look at it, rather than solicit input from a free forum.

Paul

My experience here is that there a lot of experts that help (for free) and that is as good or better than one paid "expert".[/QUOTE]

I agree totally.