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Old 23-10-2013, 12:23   #1
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hard engine mounts???

Our new to us Perkins 4.236 has hard mounts, no rubber at all. The surveyor said it was ok, but would be noisier. The engine apparently came that way, and they were renewed when the engine was removed and reworked in 98.

Why would an engine be done this way? Was it a common process? It does get quite noisy in the aft cabin, I imagine that we could convert them over to soft mounts?

Chris
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Old 23-10-2013, 12:54   #2
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Re: hard engine mounts???

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Originally Posted by witzgall View Post
Our new to us Perkins 4.236 has hard mounts, no rubber at all. The surveyor said it was ok, but would be noisier. The engine apparently came that way, and they were renewed when the engine was removed and reworked in 98.

Why would an engine be done this way? Was it a common process? It does get quite noisy in the aft cabin, I imagine that we could convert them over to soft mounts?

Chris
That does not sound right,is it metal to metal?..
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Old 23-10-2013, 13:11   #3
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Re: hard engine mounts???

Hard mount is required because of the shaft alignment. If you want to go to soft mount it might require a new shaft seal/packing and cuttless bearings. The drippless shaft seal is more forgiving than the conventional packing as the bellows will allow for movement. So before you change the mounts be sure to looking into what others things may have to be changed.
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Old 23-10-2013, 13:12   #4
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Re: hard engine mounts???

Hard mounted engines are common on commercial fishing boats.

But Tony Athens, the guru on boatdiesel says that soft mounts like those from Barry Controls will be quieter and are almost always used on recreational boats.

You can add soft mounts but you will have to rework the engine stringers.
David
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Old 05-03-2014, 12:36   #5
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Re: hard engine mounts???

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Originally Posted by witzgall View Post
Why would an engine be done this way? Was it a common process? It does get quite noisy in the aft cabin, I imagine that we could convert them over to soft mounts?

Chris
Chris, late reply I know....

Our setup is probably similar, with a largish diesel (96HP) hard mounted to the engine beds. I was surprised by this but when I finally got to talking to the guy who did the original installation he explained that he chose that system for the reliability it provided. He believed it was important in the case of a rope fouling the prop or should the boat get rolled, and he knew his stuff so I believe these are valid design choices. Similar views were expressed by CF members when I first asked about this setup a year ago.

HOWEVER, despite his good reasons for choosing this method, I am actually going to retro fit our boat with soft engine mounts, as I really have had enough of the noise and vibration. A 96HP four pot is NOT a smooth device and I have got to the point of dreading using the engine.

As stated above, I believe you would need to check compatibility along the entire drive train, from shaft coupling, to front shaft seal, and, from my reading, even the rear seal/bearing setup. Our setup with a PSS Shaft seal, a Polyflex shaft coupling and cutlass bearing seems to be reasonably compatible with soft engine mounts, but I have much more reading and phoning around to do before I am comfortable that is the case. I intend to pull the engine this year (no small task) to replace ALL of the hoses so I will do the engine mounts at the same time.

I would be interested to hear what you have decided to do.

Matt
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Old 05-03-2014, 13:22   #6
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Re: hard engine mounts???

If your concerned about the possibility of busting an engine mount from a rope wrap up or a knock down or something, it's real easy to put limiting cables or chain on the mounts. It's an old Drag racing trick, bust an engine mount drag racing and the un-restrained engine can do a lot of damage, but the chain will pull tight if the mount breaks keeping the engine roughly in place.
Safety of solid mounts, but without the noise, vibration and harshness.
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Old 05-03-2014, 23:46   #7
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Re: hard engine mounts???

Gilow, that is a huge engine for a 42 foot boat. You might have a lot less noise with half of that HP. It might be a lot easier to align a smaller engine with the shaft. Just a thought. ____Grant.
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Old 06-03-2014, 01:13   #8
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Re: hard engine mounts???

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Originally Posted by a64pilot View Post
If your concerned about the possibility of busting an engine mount from a rope wrap up or a knock down or something, it's real easy to put limiting cables or chain on the mounts. It's an old Drag racing trick, bust an engine mount drag racing and the un-restrained engine can do a lot of damage, but the chain will pull tight if the mount breaks keeping the engine roughly in place.
Safety of solid mounts, but without the noise, vibration and harshness.
Agreed. One neat way is a few wraps of 4mm 7/19 SS wire cable, around the narrow waist of each flex mount-pair, not hauled tight, of course ... made endless with a butt Talurit. Plastic-coated cable is usually white and hard to clean; as bare wire is: I would just thread some fuel hose over it before cinching up the Talurit.
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Old 06-03-2014, 02:35   #9
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Re: hard engine mounts???

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Gilow, that is a huge engine for a 42 foot boat. You might have a lot less noise with half of that HP. It might be a lot easier to align a smaller engine with the shaft. Just a thought. ____Grant.
Grant, it does seem a bit too big, that is, until you use it.

The original 60HP simply couldn't cope, the design needs at least 70+ hp to be safe, and I can't remember seeing one with less than 75HP.

There's lots and lots of freeboard and the windage that comes with it, plus we are pretty heavy for a 42 footer, 17 tons unladen in our case. I do get a little envious of the guys who come and go in the pens around me with longer boats and half the horsepower. Even the 45 footer next to me zips around with 50HP. He said the water was still swirling around his boat for ten minutes after I had left the pen.

Matt
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