What Brand of Engine Mounts

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Joined
Jan 25, 2013
Messages
1,357
Location
US
Vessel Name
Northern Lights II
Vessel Make
Bayliner 3870
I have been considering replacing all the engine mounts on the Hinos and generator, not because I know they're bad but because they're 28 years old. I know absolutely nothing about marine mounts so would appreciate some information on what to look for and what brands others have used and your experience with them good or bad. I plan on pulling the injectors and sending to a shop for testing and rebuild if needed, I want the engines running as smooth as possible. I've noticed at idle that I have things that rattle that never did before, I have 1615 hours on the mains and 1367 on the gen. Is there any advantage changing the mounts when their isn't a known problem? Thank you for your thoughts on this.


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Personally, if mounts are still within their serviceable limits I wouldnt change them.

The mounts on our 30,000 pound, twin-engine cabin cruiser were getting very tired when we bought the boat in 1998. The boat was then 25 years old. We were told by the engine surveyor that the mounts were nearing the end of their service life but they still had some time left on them before there would be metal to metal contact. This was confirmed by the friend we took with us to California to inspect, sea trial, and survey the boat. The friend until his recent retirement was the head of the engineering department at Alaska Diesel aka Northern Lights/Lugger. So he knows a wee bit about engine mounts.

Five years later an insurance surveyer noted that some of the mounts had reached the metal-to-metal stage. So we had all the mounts replaced.

This is a boat made in 1973 and it has all the vibrations machines this old and with this generation of diesels tend to develop. I have to say that the new mounts, which were very obviously putting a lot more rubber between the metal components of the mounts than the original, collapsed mounts, made not one iota of difference to the discernible vibrations of the boat.

So if you're thinking that new mounts will reduce the vibrations you feel when you run the boat, they might..... and they might not. Which is why I say replace engine mounts when the old ones have reached the ends of their service lives. Otherwise you may be changing something out that doesn't need changing yet for no discernible benefit.

There are different kinds of mounts that can noticeably reduce the vibration transmitted to an engine stringer. These are made with softer rubber. However, they can also affect the engine's alighnment. So switching to this type of mount may require a different kind of shaft coupler to be installed, one which allows the engine to move around a bit more without affecting the shaft alignment.

So make sure you get all the correct and accurate information you need from a truly credible source before making a change in the type of mount your boat was built with. That source, by the way, is not me.:)
 
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If it was my boat, I'd look at using these mounts:

Metalastik Cushyfloat Vibration Isolator | Parts | Trelleborg | Product Lines

With these couplers:

Marine Transmissions, Velvet Drive, Paragon, marine transmission parts, <marine transmissions>

Which is just what I did on my own boat, a 42' GB with 135 Lehmans. Made it super smooth running.

For the genset I'd stick with the OEM mounts but put the genset up on a platform that was held up by very soft Cushyfloat mounts.

Which again is what I did on my own boat.

Isoflex also makes very good mounts.

Isoflex - Marine Engine Mounts and Drive Couplings
 
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Natural Rubber Mounts have a theoretical performance lifespan of 20 years, in reality after about 10 years they are suspect to "performance" limitations. This means they no longer isolate vibration as intended, but still have plenty of life in them, they are just going to allow a little more vibration through to the structure. Waiting until they are metal on metal is waiting too long and by that time alignment will be impacted.

Generator mounts are easy, static load, no thrust, weight divided by 4 and pick a mount that will be loaded at approx. 70% of their maximum capacity and will provide whatever deflection you think you need.

Propulsion engines are a little more complex to choose the "best" mount solution. The weight of the engine, usually has a gear attached to the aft end which moves the CG aft, position of the mounts in relation to the CG, thrust from the shaft line and length of the shaft from the gear flange to the stuffing box or first bearing all need to be accounted for in selection.

There are easier methods, like a generic selection from a reputable company like Cushyfloat using simple guidelines. This is "wide spectrum" selection, is safe and easy, but will only be optimum by accident. These mounts are relatively inexpensive, a good value and good performers:

Cushyfloat Product Range - Trelleborg IAVS

It's time, and a good idea.

:socool:
 
Waiting until they are metal on metal is waiting too long and by that time alignment will be impacted.

Only if you assume the alignment will remain unchanged through the life of the mounts. It won't unless you have the kind of shaft couplers that compensate for changes in alignment as the mounts age. As we knew our mounts were wearing out we checked the alignment periodically to make sure it was correct. It did require a slight adjustment on occasion.
 
I would have the alignment check. If they need replacing, they should be the same kind. Shaft alignment is important.
 
Look at Poly Flex mounts.
I have them. Thought rubber mounts would act like a rubber ball and return the energy of engine movement. I concluded an engine mount should actually absorb energy ... not just reflect it.
Poly Flex mounts are not made of rubber. They are made of plastic or something very much like plastic that probably absorbs energy. And many people coment how smooth my engine is.

Phil,
Replacing most things on a boat is a golden opportunity to get something better.
 
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I would have the alignment check. If they need replacing, they should be the same kind. Shaft alignment is important.

The mounts most certainly do not have to be the same as original to achieve and maintain alignment

In fact many old mounts put on by boat builders were junk to begin with.
 
Only if you assume the alignment will remain unchanged through the life of the mounts. It won't unless you have the kind of shaft couplers that compensate for changes in alignment as the mounts age. As we knew our mounts were wearing out we checked the alignment periodically to make sure it was correct. It did require a slight adjustment on occasion.

Alignment will not remain unchanged throughout the life of an engine mount. Mounts settle over time as you noted and the manufacturers provide parameters to measure for when replacement is recommended. An easy one is if all sides of the mount are the same difference from the base. The most common mount failure is the one under the injection pump from fuel contamination.

Shaft couplings do not compensate for misalignment. The cheap ones are "drivesavers" that protect the gear from wheel impact damage, and the really good ones reduce vibration going down the shaftline. Vulcan, Centa and Rubber Design make very good shaft couplings. Grand Banks used Rubber Design for many years standard.

:socool:
 
When repowering my boat, I did some looking around at different engine mounts, generator sound shield isolation mounts, and air conditioner isolation mounts. Ended up using Soundown for the isolation mounting and sound shield material. They have very good technical support for sizing of mounts and explaining realistic expectations based on what your doing. While I haven't gotten the boat in the water to run the engine and genset yet, the difference in noise level and vibration from isolation mounting the air conditioning units is amazing!

Ted
 
Look at Poly Flex mounts.
I have them. Thought rubber mounts would act like a rubber ball and return the energy of engine movement. I concluded an engine mount should actually absorb energy ... not just reflect it.
Poly Flex mounts are not made of rubber. They are made of plastic or something very much like plastic that probably absorbs energy. And many people coment how smooth my engine is.

Phil,
Replacing most things on a boat is a golden opportunity to get something better.

True, but most times require something else to be changed modified. Had a water pump pulley replaced, which required a new water pump and motor mount modified. Anyway I try to replace with the same or closest to it. So what is wrong with metal on metal? The Eagles are sort of metal on metal with the metal spacers and metal motor mounts.
 
Phil,
Very true. Many have purchased a new high tech anchor only to find themselves modifying their bow pulpit. Changing engines can bring about quite a few necessary changes. I got by easy. Very little was luck. It was just a good fit but usually it brings about more trouble than anticipated.

Re the Poly Flex mounts ... they were as easy to install as the original 30 year old rubber mounts the builder installed.
 
So what is wrong with metal on metal?

There is nothing "wrong" with metal on metal. Commonly referred to as "hard mounted" many engines in both pleasure and commercial craft are installed rigidly, if that's what you refer to. Many may debate this but hard mounted engines are just not as quiet as resilient mounted engines.

On a resilient mount when there is metal on metal it means there is a failure of the isolation medium (Rubber, Plastic, etc) and now whatever isolation properties that were there are being short circuited by the metal on metal contact.

Note the attached. If the rubber elements in this mount fails and the top gold part is touching the black bottom part the engine in that location will move down vertically as much as 10-12 mm. This will "short circuit" any isolation properties and impact alignment.

What any good engine mount designed for marine use will do is provide "positive capture." That is if the isolation element fails the mount remains intact and the engine captive. Most marine engine mounts are considered durable driveline components and remain serviceable for 10-20 years.

All this refers to thrust taking installations, for thrust bearing installations like Aqua-Drive, Jet Drives, Outdrives, Remote gear drives, all of which are non-thrust installations, the rules are entirely different.

:socool:
 

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I want to thank everyone who responded to my question with their experience renewing engine mounts. I have bookmarked all the links and will do some serious research after the holidays when I get back to the boat. My shaft alignment is in specs, I haven't checked my low idle rpm, it's possible that it needs adjusting but I doubt it. I know the SB drive plate rattles at idle and it's on the list to be replaced this spring, might as well do the port also as they both have the same amount of time. Also I appreciate the information on sound deadening material I have some on hatches that needs to be replaced.


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There are, in fact, shaft couplers that do this. They are used with very soft and flexible engine mount systems.

O K

I'm familiar with Centa, Vulkan and Rubber Design Couplings, not familiar with a brand that says you can have gross misalignment in the shaft line.

These brands will tolerate misalignment, will reduce vibration into the structure because of misalignment, will protect things like transmission seals and bearings from misalignment, but at the expense of significantly shorter service life. Basically they sacrifice themselves for bad alignment.

I am not familiar with any shaft coupling manufacturer that says its ok have a poorly aligned shaftline when using our coupling.


Why would anyone not want to align their shaftline?

What brand are you talking about?

:socool:
 
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O K

I'm familiar with Centa, Vulkan and Rubber Design Couplings, not familiar with a brand that says you can have gross misalignment in the shaft line.



:socool:


I'm not going to do your work for you. Do what you hopefully learned in school and research it. Here's a hint--- this brand of coupler system starts with the first letter of the alphabet.
 
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The Federal couplers will allow for some misalignment and even shaft whip.

But they still require you to start with proper alignment. And I'm sure they are not happy with any gross misalignment. Especially long term.
 
I'm not going to do your work for you. Do what you hopefully learned in school and research it. Here's a hint--- this brand of coupler system starts with the first letter of the alphabet.

From an engineering perspective misalignment will create a loss of efficiency, and some component somewhere is going to have to absorb the energy loss. Could be a coupling, a gear seal, an intermediate bearing, a cutlass bearing, etc. but something will have to absorb the energy of misalignment.

As I said, shaft couplings will tolerate misalignment, they don't like it and it will shorten their service life. It's poor engineering and maintenance to not align your shaftline.

I don't need to go back to school to learn that.

Thanks for the advice though,

:socool:
 
I agree with Keysdisease on this one...

Any significant mis-alignment is wasted energy lost in the coupler that tries to correct it. Far better to put some effort into better alignment of the engine / transmission to the prop shaft. If you have a drive saver, after a long run, check the temperature of the drive saver and that heat buildup is lost energy in the drivetrain.

Stu
 
Obviously Marin's talk'in about AquaDrive but that's not a coupler that's a whole drive system. Marin's wrong on this one.

Also there used to be a coupling that did tolerate considerable misalignment. Was available in the 70's from The Bunting Brass & Bronze Co of Toledo Ohio. Called the "FlexibleCoupling". It was also a thrust bearing accomplished by the ball end of the input shaft. Radially around the "ball" are slightly curved gears turning the outer and fwd part of the coupling. Looks like at least 10 degree misalignment shouldn't be a problem. It does say in the magazine ad that it's designed to solve misalignment problems. Could have failed in the marketplace due to high gear wear. I haven't seen one ever.
 
From an engineering perspective misalignment will create a loss of efficiency, and some component somewhere is going to have to absorb the energy loss.

You are correct. But there is at least one shaft coupler system--- and very possibly others--- that is designed to do exactly what we're talking about; compensate for alignment differences. It is quite popular, at least in this area, and I'm amazed you don't know what it is. Even my dog knows the name of it. Of course he's a water dog so perhaps it's expected he would. Keep looking.:)
 
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Obviously Marin's talk'in about AquaDrive but that's not a coupler that's a whole drive system. Marin's wrong on this one.

I never would have guessed. Starts with an A, but it's not a coupling, it's a thrust bearing. The CV joints used in this system actually prefer misalignment, by design, but it must be the same degree of misalignment on both ends of the cardan shaft used in these systems. Sweet spot is 3 degrees. The mounts used in an Aquadrive system can be pure isolators because they do not have to allow for thrust. Very different from a thrust taking mount.

As manyboats noted, Aquadrives are not shaft couplings, just ask Blaney

Could that be what Marin's talking about?

:socool:
 
Of course the AD is not designed to compensate for misalignment and runs best at 1 or 3 degrees off.

The PSI coupling (two plastic discs) does tolerate some misalignment .. 5 or 6 degrees as I recall. Not manufactured by PSI ... probably an English company .. R&D. I've used them and they work well. But they don't handle 10 or 15 degrees off.

Even Marin's dog is just a dog.
 
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Could that be what Marin's talking about?

:socool:

Nope. Although when we talked to PYI about the possibility of installing Aqua Drives on our boat many years ago they referred to them as a "coupling system." So technically it is a shaft coupler albeit a multiple-component one.

But that's not the one I'm talking about.
 
Nope. Although when we talked to PYI about the possibility of installing Aqua Drives on our boat many years ago they referred to them as a "coupling system." So technically it is a shaft coupler albeit a multiple-component one.

Yeah, right, same thing, only completely different. :rofl:

I think it's time your dog starts editing/reviewing your posts. I'm guessing he'll be little more intellectually honest.
 
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Nope. Although when we talked to PYI about the possibility of installing Aqua Drives on our boat many years ago they referred to them as a "coupling system." So technically it is a shaft coupler albeit a multiple-component one.

But that's not the one I'm talking about.
Calling an Aquadrive a shaft coupler is like calling a Grand Banks a trawler. :rolleyes:


Ted
 
Calling an Aquadrive a shaft coupler is like calling a Grand Banks a trawler. :rolleyes:


Ted

Well, as you're one of the ones who's forever claiming that it is that pretty much validates PYI's term.

But you'll have to take it up with the folks we talked to at PYI. Their words, not mine.

Anyway, I don't even know how the AquaDrive got into this. It's not the coupler I'm referring to.
 
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I think it's time your dog starts editing/reviewing your posts. I'm guessing he'll be little more intellectually honest.


Oh, no, you don't want that. My dog is absolutely ruthless when it comes to telling people exactly what he thinks of them. Which, for the most part, isn't much. He'd have you in tears by the time he got done with you. I'm Mr. Tactful compared to him. You should read some of the stuff he posts to OTDE.
 
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So what kind of engine mounts does your dog use Marin?
A doggone good mount I'm sure.

Most of the old marine engines of the 50's were so smooth they didn't need flexable mounts. Almost all were bolted directly to the wood or steel engine beds. Very heavy crankshaft and even heavier flywheel. And the flywheel was on the front of the engine .. along w the starter and generator. Almost all were very low profile "flat head" designs that had the camshaft and valves under the head. Not very efficient but they were close enough that the OHV engines freqiently came up inferior due to other aspects of vehicle design.

A 52' CC yacht of the day had three 160hp flathead six cyl engines and made over 20 knots.
 
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