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Engine mounts for Perkins 3.152


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Hi, my narrowboat has a 1960's Perkins P3.152 engine. It has had various issues since I got the boat last year, but that's another story. Anyway, the old engine mounts were worn and have been replaced, but the engine still shakes (fine at tick over, bad at mid-range) and the vibration inside the boat is pretty harsh. 

I realise that there may be a number of causes other than the mounts and alignment and compression have been checked. However, I have alternative advice from two engineers - both of whose views I respect - with one saying that an old heavy engine like this is best solid mounted.

Can anyone with experience of this engine type tell me what they found to be the best solution?

Thanks, Paul

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Our boat has a D3.152 which is mounted onto  4" x 3"(approx) oak bearers which in turn are bolted onto the engine beds.

The engine beds are something like 10 x 5 angles running along the engine room.

This set up has been fine for us from tick over at 500rpm to 1400rpm which takes us to 7mph on the river.

 

When we first saw and tried the engine in the workshop  before we purchased it it was standing on a fairly lightweight cradle and it seemed smooth enough through the range.

We had a problem with drive line vibration when we got onto the  canals  but once we got the drive plate sorted all has been OK.

 

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I would have thought it quite unusual to have a P3 other than solid mounted.

An arrangement like JohnB talks about where it is on hardwood, and then the hardwood on the steel bearers sounds about right to me, and will probably be better than straight onto the steel.

 

Not an engine I think I would want on flexible mounts of any sort.

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2 hours ago, Paul Conroy said:

Thankyou, and did you need to do anything to stop vibration transmitting through to the cabin other than the drive plate?

I have a similar installation to JohnB-oak bearers approx 4 1/2 × 3 onto steel bearers (Engine is Sabb 2J). 

As it was my own setup I decided to try sandwiching some 100mm x12.5mm Tico between the two- which is a vibration absorbing mat for heavy machinery. This was actually suggested to me many years ago by Tony Tucker, a well known marine architect/surveyor and a man who I hold in high regard as knowing his stuff.

I cant say for sure if its actually better or not as havent tried it without- but my installation is certainly alot smoother and quieter than many modern installations with rubber mounts and the washing machine produces far more vibration through the boat than the engine ever does!

https://shop.deltarubber.co.uk/tico-s-anti-vibration/tico-s-antivibration-mounting.html

 

Edited by PaulJ
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The driveline vibration was in fact a banging noise like rattling a half brick in a bucket :-) it didn't shake the boat just stopped us engaging gears at  low engine  speeds; so we had to wind the speed back down after putting into gear at higher revs. We have separate speed wheel and gear change so not impossible in practice but a pain that got fixed as soon as we got onto the canal system!

The Tico is a good idea and I have used it successfully for higher frequency noise on heavy machine tools -- I did get some pads ready for  when we were getting the engine setup and running, but, I never got round to trying them out.

It might be a good idea also to check that the engine sits evenly on all four feet; try rocking it on the diagonals to check.

I should mention this is a traditional engine room with a universal joint propshaft under the back cabin floor.

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If mounting the engine on timber, softwood is better than hardwood.  It has a greater damping effect.  Ideally 4x4 or bigger Douglas Fir or clear Yellow Pine.

Spread the weight of the engine with steel plates about 4 in  square.

 

 

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On 20/07/2019 at 16:18, BEngo said:

If mounting the engine on timber, softwood is better than hardwood.  It has a greater damping effect.  Ideally 4x4 or bigger Douglas Fir or clear Yellow Pine.

Spread the weight of the engine with steel plates about 4 in  square.

 

 

And bolt the engine to the timbers, recessing the engine bolt heads on the underside of the timbers, and separately bolt the timbers to the engine beds, so there is no direct metal to metal contact between engine and beds.

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It's Just occurred to me!

When fixing  the engine down  I made slots under the timber bearers to allow the spreader plates and nuts to be fitted with the engine in place.  (my spreader plates are threaded for the bolts)

The bolts can then be dropped in from the top of the feet and the engine doesn't need lifting  for assembly  :-) ,and it avoids a lot of juggling.

The bolts ,of course need to be arranged to NOT touch the metal bearers.

 

The same goes for the bolting down onto the boat steel work...

Then the engine can be slid along the beds using the timber as a sled.

Useful for maintenance  and easier for fitting shims if needed

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5 minutes ago, JohnB said:

It's Just occurred to me!

When fixing  the engine down  I made slots under the timber bearers to allow the spreader plates and nuts to be fitted with the engine in place.  (my spreader plates are threaded for the bolts)

The bolts can then be dropped in from the top of the feet and the engine doesn't need lifting  for assembly  :-) ,and it avoids a lot of juggling.

The bolts ,of course need to be arranged to NOT touch the metal bearers.

 

The same goes for the bolting down onto the boat steel work...

Then the engine can be slid along the beds using the timber as a sled.

Useful for maintenance  and easier for fitting shims if needed

I think I welded spreaders on the bolts under the head and then dropped the engine on the bolts, that way the nuts lift the bolt heads clear of the steel work. I have considered butting half inch thick rubber mat in the sandwich but never got round to it

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Yes good point. I try for the easy way though ;-)   bolts dropped down  allows for fitting one at a time and avoids trying to line up four things at once.

  An extra washer under the bolt head will lift it up for some more clearance, And a thin disk on the angle grinder will make quick work of trimming to length.

In some more engineered installs they would bore a "rattling fit hole"  in the bearer for the bolt end to pass through.

 

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6 minutes ago, JohnB said:

Yes good point. I try for the easy way though ?   bolts dropped down  allows for fitting one at a time and avoids trying to line up four things at once.

  An extra washer under the bolt head will lift it up for some more clearance, And a thin disk on the angle grinder will make quick work of trimming to length.

In some more engineered installs they would bore a "rattling fit hole"  in the bearer for the bolt end to pass through.

 

You have me thinking now, I will check next week. Are you still East Anglian waterways?

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Best I can do for the moment, Hope that will explain....

 

The picture here was taken when we moved the hull from the builders and the engine was just bolted down for transit.

This is the rear Stbd. mount - its part of  our gearbox housing, the other feet are similar but different ;-)

 

The finger points to the engine bolt which is now fitted from the top as described by the sketch.

Mount Sketch.JPG

Engine mount.jpg

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4 minutes ago, JohnB said:

Best I can do for the moment, Hope that will explain....

 

The picture here was taken when we moved the hull from the builders and the engine was just bolted down for transit.

This is the rear Stbd. mount - its part of  our gearbox housing, the other feet are similar but different ?

 

The finger points to the engine bolt which is now fitted from the top as described by the sketch.

Mount Sketch.JPG

Engine mount.jpg

Very similar but neater than my setup

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