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Old 03-04-2016, 09:56   #16
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Re: Perkins Diesel breaking engine mounts

when aligning an engine to the prop shaft all the mounts hold downs should be tight. and only loosened to make adjustments. if you have to lower, say aft starboard, then you'll have to raise fwd port and so forth. I've seen broken "new" mounts and the cause was adjusting one and not the others. Hence applying undue weight on some of the others. when adjusting make sure the weight is evenly dispersed on all mounts then tighten the top nut and check alignment again. if your adjusting one too far with the adjusting nut, you will weaken it shim the foot instead. the nuts are for final adjustments.

also are the new brackets installed correctly? this can cause lateral forces and brake mounts.
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Old 04-04-2016, 02:01   #17
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Re: Perkins Diesel breaking engine mounts

Hi,
its like a table with two legs shorter than the other two and it will rock.
If it is square on the bearers and the is no dramatic vibration and noise,and you
have checked all the other points mentioned.
Are you sure there is no flexing of the hull and the bearers have not been damaged?
If everything that has been mentioned is checked as O.K. It could be the poly mounts
are too hard ,if they shatter and have broken the mounts there is a serious problem
somewhere, beefing up the mounts in strength may not be the answer,they may need
to be softer to absorb the vibration.
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Old 04-04-2016, 18:04   #18
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Re: Perkins Diesel breaking engine mounts

I just wish that once this problem is solved that the owner mentions what was found to solve this problem. Most of the time the owners do not publish a comment due to problem being so simple... and or fear of being ridiculed. We alllllllllll learn from our mistakes... Roger
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Old 04-04-2016, 18:26   #19
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Re: Perkins Diesel breaking engine mounts

Quote:
Originally Posted by GazzaAntipodes View Post
I have a Perkins P 3 144 engine in my 38 foot yacht. I keep on breaking poly flex mounts and engine mounts and I am at my wits end.
I have had engineers check the alignment, I have slipped and pulled the shaft which had no deflection or error, there is a flexible coupling between the gearbox flange and shaft. The cutles bearing is good.
After a 200 mile trip with new mounts the front port mount and aft starboard mounts had shattered the steel plate between the poly / rubber insert and the lock nut.
I have new and heavy engine brackets for the mounts, the engine when running appears to have little vibration but must be something there to be doing this damage.
My hope is someone may have experienced this issue and can point me in a direction to fix this issue once and for all.
I am starting to think the issue may be with the engine and the harmonic balance, or in the gearbox as I have mechanical box.
Any clues would be appreciated!
Cheers.... It's driving me to drink not my next island
Assuming you have a typical mount arrangement and alignment is good I'd check for resonance at a particular rpm.

You can check this visibly or with a 3 axis accelerometer.

Could also be mismatched mounts. If you are inadvertently preloading a mount then early failure is likely.

Without pics of the arrangement and of the failed mounts it's dificult to be more specific.

Do you have any non standard loads or appendages hanging off the motor?

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Old 04-04-2016, 18:35   #20
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Re: Perkins Diesel breaking engine mounts

Quote:
Originally Posted by GazzaAntipodes View Post
I have a Perkins P 3 144 engine in my 38 foot yacht. I keep on breaking poly flex mounts and engine mounts and I am at my wits end.
I have had engineers check the alignment, I have slipped and pulled the shaft which had no deflection or error, there is a flexible coupling between the gearbox flange and shaft. The cutles bearing is good.
After a 200 mile trip with new mounts the front port mount and aft starboard mounts had shattered the steel plate between the poly / rubber insert and the lock nut.
I have new and heavy engine brackets for the mounts, the engine when running appears to have little vibration but must be something there to be doing this damage.
My hope is someone may have experienced this issue and can point me in a direction to fix this issue once and for all.
I am starting to think the issue may be with the engine and the harmonic balance, or in the gearbox as I have mechanical box.
Any clues would be appreciated!
Cheers.... It's driving me to drink not my next island
How is it going ? I have some more suggestions but need to know how the last suggestions went.
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Old 04-04-2016, 18:53   #21
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Re: Perkins Diesel breaking engine mounts

I have some more suggestions but need to know how the last suggestions went.

I am also wondering... I thought maybe some pictures would have appeared by now... this is an interesting one...
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Old 04-04-2016, 20:13   #22
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Re: Perkins Diesel breaking engine mounts

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Originally Posted by GazzaAntipodes View Post
Also the boat is a 38 ft fibreglass cutter rig sloop, I built her 30 years ago, engine is regular serviced. This issue started when I broke a forward mount foot coming over a bar, since repairing the bracket and mount it has been constant
Reluctant even to suggest it but... could bouncing on the bar have caused hull damage you haven't found yet?

Less likely with a full keel but I'd think the aft end of even a long fin keel would tend to kick upwards into the hull and possibly cause internal separation of the laminate.

If that did happen the engine might be kicked backwards rather than forwards and be likely to break a forward mount. Engine being thrown forwards by a sudden stop would more likely break a rear mount I think.

Sounding with a rubber mallet ought to find a delaminated area if it's there.

Hoping this is all nonsense though and that you've already found and fixed the issue
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Old 08-04-2016, 23:39   #23
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Re: Perkins Diesel breaking engine mounts

I have discovered the cause of the vibration, the thrust bearing has been worn for a while, and rattling around in the gearbox also the pulley was OK in low revs but as they increased it was wobbling all over the place, hence the vibration and destruction of the mounts.
The solution is to repower which I am starting to organise a Volvo D2 40 hp. With a gearbox ratio of 2.63:1
I have gone with the Volvo as it is a Perkins engine, about a third of the size and weight. Modifications to be done to the engine beds, allowing 5 days on the hard to do the job.
I thank everyone for their help and input in helping me to resolve this annoying expensive problem.
Fair winds and calm seas to all
Gazza
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Old 09-04-2016, 16:27   #24
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Re: Perkins Diesel breaking engine mounts

Thanks for the feedback. How did was it diagnosed?

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Old 09-04-2016, 18:03   #25
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Re: Perkins Diesel breaking engine mounts

My next suggestions were going to be a bit more serious.
If you pull the motor out and strip it, I would be very interested if the crank is in 2 pieces!
Broken at the fly wheel journal.I would not be at all surprised.
Just wriggle the flywheel in place it will just fall off,Maybe!!
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Old 09-04-2016, 21:05   #26
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Re: Perkins Diesel breaking engine mounts

When I arrived in Mackay Qld. I arranged a diesel engineer to inspect the engine and when we ran it up it was looking ok on idle and low revs,maps we picked up the revs, the crankshaft pulley was all over the place and a rumble in the gearbox, and vibration could be felt.
It has been a good reliable engine, hopefully the Volvo will be the same.
Thanks again for evryones input and fantastic knowledge base
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Old 09-04-2016, 23:49   #27
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Re: Perkins Diesel breaking engine mounts

Just as I thought. A good visual shot of the workings is all it takes, sometimes.
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