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Engine seems to be getting louder


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You don't need a crane, an old car scissor jack and lots of pieces of wood packing will do but don't just bung it under the engine and crack something expensive. In fact changing mountings is not straightforward.  You will probably have to lift the engine quite high to get the mountings out. There will be tears, bad language, squashed fingers and more.  As Tony says, the diagonal alignment could well be out but 3 out of 4 are probably OK so I would just try winding the one corner up a couple of threads and see how it goes. If at some stage you decide to change some mounts I would pay someone to do it. Its more than skill and art, it involves slaughtering chickens, pentagrams and prayers to the dark lord.

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3 hours ago, Tracy D'arth said:

You need to get all that oil sorted out too, it will wreck your new mounts. They will rot if oily.  Is it a leak or spillage?

 

The bund under the engine became flooded a couple of weeks ago and coated the bilge (and the mounts) in oil. I cleaned out the bilge so as not to pump oil overboard but I need to clean more, especially if the oil could be damaging the mounts. The thread from one of the brass bolts holding my stern gland was stripped, and water trickled in that way. My bilge pump is manual. In fact come to think of it perhaps the stripped bolt was also the result of the engine vibration?

 

I'll trial and error the corner i messed with and see if i can improve the vibration further. But I'm certainly in no hurry to get new mounts if it isn't absolutely necessary, the noise an vibration is much better now. Unless you'd strongly advise more urgency I'll get them checked next time I black the boat which will be in a year or so.

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8 hours ago, jetzi said:

 

The bund under the engine became flooded a couple of weeks ago and coated the bilge (and the mounts) in oil. I cleaned out the bilge so as not to pump oil overboard but I need to clean more, especially if the oil could be damaging the mounts. The thread from one of the brass bolts holding my stern gland was stripped, and water trickled in that way. My bilge pump is manual. In fact come to think of it perhaps the stripped bolt was also the result of the engine vibration?

 

I'll trial and error the corner i messed with and see if i can improve the vibration further. But I'm certainly in no hurry to get new mounts if it isn't absolutely necessary, the noise an vibration is much better now. Unless you'd strongly advise more urgency I'll get them checked next time I black the boat which will be in a year or so.

 

The red bit suggests the alignment has been well out. Are you aware most gearboxes give the  maximum radial misalignment as zero and the angular misalignment as about 0.005". Most so called flexible are no such thing in respect of misalignment, especially radial.

 

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29 minutes ago, Tony Brooks said:

 

The red bit suggests the alignment has been well out. Are you aware most gearboxes give the  maximum radial misalignment as zero and the angular misalignment as about 0.005". Most so called flexible are no such thing in respect of misalignment, especially radial.

 

If the shaft and stern bearing alignment is not correct and you do not have either an Aquadrive or a Python drive continuing to run the engine will do huge and expensive damage to the stern gear, gland, shaft and gearbox.

 

Lets have that photograph so we can see what you have.

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45 minutes ago, Tony Brooks said:

 

The red bit suggests the alignment has been well out. Are you aware most gearboxes give the  maximum radial misalignment as zero and the angular misalignment as about 0.005". Most so called flexible are no such thing in respect of misalignment, especially radial.

 

 

 

To reinforce Tony's comment my PRM gearbox manual states 0.05mm, which is actually 0.002"

Correct installation is crtical.

 

 

Screenshot (315).png

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I bet many, many, gearboxes don't get anywhere near that sort of accuracy and rubber mounts could make the whole thing worse. If half a ton of engine is wobbling about plus there will even be a bit of fore and aft movement it takes a pretty good coupling to cope with that. Aqua/Python drives will handle that and the fore and aft too but it is a problem that needs careful thinking about. If you have a long shaft supported by plummer blocks you need to think about flexibility. thrust and wear on the stern gland and the gearbox all the way along the thing. Might not be a problem for most installations but mid engined boats (like mine) or boats where the engine is mounted ahead of a back cabin need to think about it.

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I retro fitted a Python Drive to Innisfree and the difference was amazing, no more alignment issues, much quieter, hardly any vibration and a leak proof sten gland that never needed adjusting. 

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13 minutes ago, Bee said:

I bet many, many, gearboxes don't get anywhere near that sort of accuracy and rubber mounts could make the whole thing worse. If half a ton of engine is wobbling about plus there will even be a bit of fore and aft movement it takes a pretty good coupling to cope with that. Aqua/Python drives will handle that and the fore and aft too but it is a problem that needs careful thinking about. If you have a long shaft supported by plummer blocks you need to think about flexibility. thrust and wear on the stern gland and the gearbox all the way along the thing. Might not be a problem for most installations but mid engined boats (like mine) or boats where the engine is mounted ahead of a back cabin need to think about it.

 

I think the long shaft installations on narrowboats (and may other boats come to that) were originally designed for engines bolted straight onto the beds so they could not wave about. It seems to me that flexible mountings only really became popular since about the 1960s when more and more automotive engines were marinised. A solidly mounted engine properly done gets rid of all the thrust movement and alignment problems.  Otherwise, I don't understand why Aquadrive type two points of flexibility couplings are not more or less standard fitment - apart from cost and maybe space.  

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4 minutes ago, Tony Brooks said:

 

I think the long shaft installations on narrowboats (and may other boats come to that) were originally designed for engines bolted straight onto the beds so they could not wave about. It seems to me that flexible mountings only really became popular since about the 1960s when more and more automotive engines were marinised. A solidly mounted engine properly done gets rid of all the thrust movement and alignment problems.  Otherwise, I don't understand why Aquadrive type two points of flexibility couplings are not more or less standard fitment - apart from cost and maybe space.  

 

Refering again to the PRM manual, they say that ideally flexible couplings (gearbox to engine) should not be used unless the engine is mounted on flexible mounts.

 

 

 

Screenshot (317).png

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2 minutes ago, Tony Brooks said:

 

I think the long shaft installations on narrowboats (and may other boats come to that) were originally designed for engines bolted straight onto the beds so they could not wave about. It seems to me that flexible mountings only really became popular since about the 1960s when more and more automotive engines were marinised. A solidly mounted engine properly done gets rid of all the thrust movement and alignment problems.  Otherwise, I don't understand why Aquadrive type two points of flexibility couplings are not more or less standard fitment - apart from cost and maybe space.  

I think you're right. The idea of putting some great big thumper on wobbly mounts and watching a great big cast iron flywheel flailing about fills me with dread.

 

8 minutes ago, nb Innisfree said:

I retro fitted a Python Drive to Innisfree and the difference was amazing, no more alignment issues, much quieter, hardly any vibration and a leak proof sten gland that never needed adjusting. 

Many of the posts on here are about worn glands, repacking, leaks and stuff like that. I have a Python drive (from new) and in more than 10 years  have never had any problems at all with the stern gland.

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2 minutes ago, Bee said:

Many of the posts on here are about worn glands, repacking, leaks and stuff like that. I have a Python drive (from new) and in more than 10 years  have never had any problems at all with the stern gland.

 

Absolutely on the button. My Bukh certainly had a great big flywheel waving about and it was a three cylinder so despite its harmonic balancer putting in on flexible mounts would not seem to be a good idea but that was the way the Bukh agents recommended. However, it was fitted with an Aquadrive  with the result of 10 years in hire fleets then I bought it. Adjusted the gland at that time and never again in the next 20 years. I did have a mount fail (oil damage) but with the Aquadrive changing it was a simple bankside lever up, slide out and slide the new one in. This was helped by the mounts not having a long adjusting stud but no shimming or alignment to worry about.

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On 08/05/2021 at 09:57, Steve56 said:

Once the idle speed has dropped of just a little it can introduce vibration and rough running.

 

That's true at idle, but would go away at increased revs if it was the issue.

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14 hours ago, Tracy D'arth said:

You need to get all that oil sorted out too, it will wreck your new mounts. They will rot if oily.  Is it a leak or spillage?

I've wiped up the oil around the mounts with oil absorbent pads. I used it like dental floss to get under the cap and a bit of sticky black stuff (not oil) got stuck to the pad, I guess this is a bit of melted rubber?

 

The one mount (to the fore of the boat, opposite the one that was loose) seems worse - I can actually see and feel bits of rubber coming out there. Here's a photo:

 

RubberOutOfBottomOfStbdForeMount.jpg.fe390850932902dd7cda01115884a0aa.jpg

 

 

 

I guess this does mean I need new engine mounts.

 

I will have to look for a boatyard willing to do the job. Honestly I find it near impossible to get anyone to work on the boat. There seems to be more work than anyone knows what to do with so even if you find someone with availability, they prefer to do nice clean easy jobs.

 

14 hours ago, Tracy D'arth said:

Can you sent a pix of the coupling and shaft behind the gearbox?

 

Yes, here are pictures. In the second picture I'm holding the stripped brass bolt that I replaced, in case that's a clue for how the gland was wearing.

 

I also uploaded a video of me rotating the shaft with my hand. I don't suppose you would be able to judge a couple of millimetres of misalignment from it, but it's at this link: https://imgur.com/a/ivoqOeY

 

Transmission.jpg.ba9555701bf3f37932dd095e1db6da8b.jpgSternGlandStrippedBolt.jpg.311b88dbdc3c38c1c66537683cf646f2.jpg

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So you have an Aquadrive, forget about alignment, it does not matter if its a clog out.

 

Your noise is that rotted engine mount, the metal skirt is touching the engine bearer. If this is the only bad one, just change that one. Its a DIY job now that you do not have to line the shaft up.

 

The stripped bolt will not be due to vibration. Probably ham fistedness.

 

The stern gland is near due for repacking, another DIY job, loads of post on how to do it on here.

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Good news - its a Pythondrive or Aquadrive so accurate shaft alignment is not an issue. in fact it should run slightly out of alignment.

 

Yes the mounts  need renewing but there is no need for accurate shaft alignment. Just set the lower nuts on the new mounts to a similar position to the old ones. That won't help with diagonal support but it should be near enough.

 

 

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1 hour ago, TheBiscuits said:

 

That's true at idle, but would go away at increased revs if it was the issue.

Which is what the op seemed to be suggesting when he said if he got the speed just right then there was an improvement. Although this is now irrelevant as it appears the mounts were at fault.

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1 hour ago, Tracy D'arth said:

you have an Aquadrive

 

1 hour ago, Tony Brooks said:

its a Pythondrive or Aquadrive

 

For the record, which part is the aquadrive? Is it the concertina black rubber thing?

 

1 hour ago, Tracy D'arth said:

Your noise is that rotted engine mount, the metal skirt is touching the engine bearer. If this is the only bad one, just change that one. Its a DIY job now that you do not have to line the shaft up.

It's much quieter since I tightened the bolt. I don't think the metal skirt is quite touching the bearer but it is close.

 

Is there any harm in hanging on for a few months or should I replace the mount urgently?

 

35 minutes ago, Steve56 said:

Which is what the op seemed to be suggesting when he said if he got the speed just right then there was an improvement. Although this is now irrelevant as it appears the mounts were at fault.

Yeah, it seems that if I got the revs just right then the engine wouldn't move aound so much, even with the loose mount bolt. I think this was a valid theory, but yeah definitely seems to be the mounts.

 

I've always (since the last 3 years of owning her) found that tickover is quite vibratey and noisy. I wouldn't want to increase the tickover revs though as I'm sure I'll get lots of fistwaving as I pass moored boats.

 

Since the alignment seems to be not an issue, I'm going to take her for a cruise now and see how she goes. I will check if the stern gland gets warm and see how the vibration goes at a variety of RPM. Is there anything else I should keep an eye out for?

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The Aquadrive is the length between the gearbox coupling and the green half coupling.

 

There is no need for urgent replacement of you can stand the noise and vibrations. It can't damage the stern gear.

 

The gland will not get that warm unless the fitting of the Aquadrive was cocked up.

 

The Aquadrive might be a Pythondrive. Pretty much the same thing but different companies.

 

 

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10 minutes ago, Tony Brooks said:

The Aquadrive is the length between the gearbox coupling and the green half coupling.

 

There is no need for urgent replacement of you can stand the noise and vibrations. It can't damage the stern gear.

 

The gland will not get that warm unless the fitting of the Aquadrive was cocked up.

 

The Aquadrive might be a Pythondrive. Pretty much the same thing but different companies.

 

 

Definitely an Aquadrive.

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Just a quick note about the OP's surging (not holding steady revs) could it be as simple as it being time for an oil change?

with our engine (lpws4) which was only meant to have 100 hours between changes we found that from 85 hours onwards it wouldn't hold our usual cruising rpm, started as being barely noticeable and slowly worsened as the hours went towards 100.

By the 100 hours our cruising speed of 1250 rpm would vary by about 25 rpm each way (1225 - 1275)

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On 08/05/2021 at 21:19, Bee said:

You don't need a crane, an old car scissor jack and lots of pieces of wood packing will do but don't just bung it under the engine and crack something expensive. In fact changing mountings is not straightforward.  You will probably have to lift the engine quite high to get the mountings out. There will be tears, bad language, squashed fingers and more.  As Tony says, the diagonal alignment could well be out but 3 out of 4 are probably OK so I would just try winding the one corner up a couple of threads and see how it goes. If at some stage you decide to change some mounts I would pay someone to do it. Its more than skill and art, it involves slaughtering chickens, pentagrams and prayers to the dark lord.

Looking at those mounts, I think that the flats on the top of the stud mean you would be able to unscrew it from the mount. If you do one at a time, loosen the top and bottom nuts, unscrew the stud from the base and lower nut, unbolt the base and remove. Replacement is a reversal of the above, but after replacing the base, do not bolt it tight until you have the mount reassembled.

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