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Old 10-14-2017, 11:45 PM   #1
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New engine mounts - Aquadrive, Isoflex, or something else?

Hi Guys,

I need some new, soft engine mounts. I have Avadrive thrust bearings on each shaft, and currently Aquadrive mounts.

I need new mounts, and want to source best available. Any views/ thoughts as to whether to go with Aquadrive again, or change to Isoflex (which is what a lot of people here in Brisbane seem to sell), or change to something else?

Thanks for your thoughts.

Hamish.
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Old 10-15-2017, 01:18 AM   #2
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Mine are Dual Flex. I have had no issues with them at all. Not sure if they are available here, mine were purchased in USA and fitted at Port Townsend, Washington. I have the 1500-1800 # model.
Bushings Inc. engine mount cross reference chart
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Old 10-15-2017, 07:04 AM   #3
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Here in the US Aquadrive (Sweden) uses Trelleborg (UK) mounts.

The System

Trelleborg Cushyfloat

Cushyfloat Product Range - Trelleborg IAVS

While Cushyfloat mounts are thrust taking , which is an unnecessary feature for an Aquadrive system, they are very good isolation mounts.

For direct replacement you could identify the physical size in the chart linked to above, find the durometer (shore) stamped into the base as pictured, and go shopping for price rather than buy replacements from Aquadrive ($$$)

It will be difficult to get more than just a marginal improvement with any other brand thrust taking mount. For that you need a non-thrust taking mount which are typically conical shaped and often have a higher profile than your mounts.

Direct replacement is easy. Choosing a different mount may involve dealing with different heights, mounting holes, stud size, etc.

In the end unless you choose a different mount using weight of the engine/gear combination, center of gravity of the combination, mount locations as they relate to the C/G, gear ratio and torque, than you may still have the installation challenges of a different size and shaped mount for a marginal improvement.

All this is considering the installed mounts were sized properly.

One last bit, if you do choose a different brand, if it doesn't look like it has at least as much rubber (or whatever isolation medium) as your current mounts, any claims of better performance are questionable IMHO

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Old 10-15-2017, 07:08 AM   #4
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Just be sure when mounting the engine there IS some misalignment.

The flexing keeps the units lubed.
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Old 10-15-2017, 08:28 AM   #5
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Check the specs for your particular Aquadrive, typically the alignment between the gear and the Aquadrive call for 1* to 5* misalignment, with 2-3* being the "sweet spot."

FF is correct, there needs to be some misalignment, but more than 5* will impact lifespan of the CV joints.

But there are variations within the Aquadrive units and models, so check-specs




Quote:
Originally Posted by FF View Post
Just be sure when mounting the engine there IS some misalignment.

The flexing keeps the units lubed.
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Old 10-15-2017, 10:04 AM   #6
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To the OP: Why are you replacing mounts?

What brand are installed now?

Going to a different brand can be quite an undertaking as geometry of brackets/holes/etc will be different.
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Old 10-15-2017, 10:45 AM   #7
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"FF is correct, there needs to be some misalignment,"

Dont ask how I learned this!
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Old 10-15-2017, 11:01 AM   #8
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I've had boats w vibration problems and soft mounts.
Ive had boats w fairly stiff mounts and very low vibration.

Like most other things in boating ... variables. Lots and lots of variables. I can hardly see my 4cyl engine vibrating now w fairly stiff mounts even at low rpm. But I feel very little vibration. It may be that the material they are made of actually absorbs vibration. Rubber does not. If you drop a rubber ball on a hard surface it will bounce back. If a ball is made out of material that absorbs vibration the ball should hardly bounce at all. Silly putty? Silly example.

The mounts I put in Willy are Poly Flex. I heard some good things about them from a good source and ordered them. I have a smooth running boat but as I said above .. variables. For example if your boat has a stiff and heavy structure under her engine it will tend to run smooth. And lots of other variables are playing a part. The Poly Flex mounts were selected for my boat and engine by a Poly Flex distributer. They work in my boat. Excellent. And they are 10 years old. I do see some rust on the metal housing though.
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Old 10-15-2017, 04:14 PM   #9
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Hi All,

Thanks for the helpful replies.

Keysdiseasae, yes that is the same Aquadrive system (mounts + thrust bearing/coupling) which I currently have in my boat.

Why am I thinking of changing mounts? 3 reasons:

First, the thrust bearing/coupling on each side is starting to deposit tiny flecks of disintegrated rubber on the hull after each use. Basically the rubber is dried up and brittle, so I need to pull the thrust bearings/couplings out and have a 'kit' put in each, consisting of new rubber bits + seals + bearing and then re-grease. So I will be doing work on the shafts and needing to redo alignment and all that stuff anyway.

Secondly, at least 2 of the 8 current engine mounts look to me (and to the mechanic) to be very dodgy. You sort of have to bend down and look up under the metal shroud which shields the top of the mount. The rubber looks to be both hard and also squashed. Unsurprisingly, the dodgy looking ones are located next to the raw water pumps which have been leaking (see separate post on that subject).

Finally, I just replaced the mounts on the gensent and doing so has made a HUGE reduction in vibration. It was really surprising. I just got regular Cummins mounts - the new ones were a little supple/squishy, whereas on the ones we removed the rubber ring was compressed and literally as hard as steel.

I have noticed my boat vibrated more than comparable boats of the same model, the new genset mounts have fixed that when we are on the hook with the gen on. And the genset is the same age and wear as the engines, so if one lot of rubber is shot you have to suspect the others as well...

Agree also that the easiest job is simply to replace like with like (ie go with Aquadrive mounts again), but as I only plan to do this job once in the next decade, if there are newer or superior products available these days such as IsoFlex or Polyflex then I would like to investigate that option first.

Finally, thanks to those who mentioned the requirement for slight misalignment. I have read that in the literature as well, and will be making sure the installer is fully aware!

Thanks,

Hamish.
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Old 10-15-2017, 05:06 PM   #10
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Hamish,

I'd talk to the people at Polyflex. They are a Brisbane based company, and have a huge range of marine engine mounts.
Poly Flex Group - Advanced Polymer Technology for Vibration Control - Search
I dealt with them when deciding on a flex coupling and found them very helpful.
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