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Is an Aquadrive Worth It?


Old Son

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I have a 5year old Centreflex type fitting on the back of my PRM 150, a plummer block midway along the length of my 550mm long 40mm dia prop shaft and terminating through a standard stern gland with manual greaser connected.

I am thinking I want to fit an Aquadrive unit.  Do you think it would have any benefits or is my current set up more than adequate?

Thanks

 

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THe alternative is a Python Drive - cheaper, also when I fitted mine it was shorter than the Aquadrive which made it easier to fit in.

I am a fan of the Python Drive; it makes the engine quieter, and the thrust from the propeller goes directly to the hull, rather than going through the gearbox and engine and pushing the boat through the engine mounts.  The engine is therefore less prone to shaking about and the engine mounts will last much longer.  The alignment of the engine is also less critical, although you still have to set up the engine mounts properly.

PM me an email address and I'll send you a draft of a magazine article I did when i fitted mine.

Edited by dor
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3 hours ago, dor said:

THe alternative is a Python Drive - cheaper, also when I fitted mine it was shorter than the Aquadrive which made it easier to fit in.

I am a fan of the Python Drive; it makes the engine quieter, and the thrust from the propeller goes directly to the hull, rather than going through the gearbox and engine and pushing the boat through the engine mounts.  The engine is therefore less prone to shaking about and the engine mounts will last much longer.  The alignment of the engine is also less critical, although you still have to set up the engine mounts properly.

PM me an email address and I'll send you a draft of a magazine article I did when i fitted mine.

As Dor says Its the thrust bearing that makes the whole thing worthwhile and then engine can wander about wherever it wants. I have a Python drive and its been fine but they are expensive. If your installation has worked OK for some years and the plummer block is nicely aligned with the stern gland with no bad wear I would be tempted to leave it alone until you need to do some sort work on the engine / gearbox in the future then a Python / Aquadrive will make a better installation.

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The issue I have is that the plumber block holds the propshaft straight and aligned to the stern gland but the centreflex does not have the ability to take up any misalignment with the engine. The engine is on rubber mounts and so will move about a bit. I can have an Aquadrive supplied and fitted for about £900 all in, maybe a saving of £50 if I go for a Python Drive. Is the setup I have sufficient to protect the engine and gearbox from the stresses from the prop. If something breaks the cost of the new drive will still have to be found plus the cost of repairs to whatever breaks!

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6 minutes ago, Old Son said:

Is the setup I have sufficient to protect the engine and gearbox from the stresses from the prop

Yes - if it is installed properly

And Aquadrive means you don't have to bother so much about alignment. 

Richard

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It depends to some extent on how much you use the boat, and how well installed the current set up is.

We've got both in our fleet and to be honest you don't notice a lot of difference from the user perspective.

Maintenance wise the Python drive set up is a dream - for example if a mount fails there are no unintended consequences when the engine starts hanging on the shaft, and engine removal/refitting is quicker.

Stern gear life is definitely extended with the Python drive - I've not yet re-bushed a stern tube or changed a shaft on any of the Python fitted boats and some are at over 10000 hours now.

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26 minutes ago, Old Son said:

The issue I have is that the plumber block holds the propshaft straight and aligned to the stern gland but the centreflex does not have the ability to take up any misalignment with the engine. The engine is on rubber mounts and so will move about a bit. I can have an Aquadrive supplied and fitted for about £900 all in, maybe a saving of £50 if I go for a Python Drive. Is the setup I have sufficient to protect the engine and gearbox from the stresses from the prop. If something breaks the cost of the new drive will still have to be found plus the cost of repairs to whatever breaks!

I, and doubtless many others would like to know who can fit an Aquadrive for £900.  

That aside, I've said many times you will forget the cost very soon after you experience the difference a proper flexible drive ie Aquadrive/Python drive makes.  

A number of hire boat operators fit them as standard, Black Prince have always done so, I think.  

It's generally accepted that the Aquadrive is the more durable unit, but one hire boat operator I spoke to last year reckons it's a six and two threes as the Python is cheaper.

 

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1 hour ago, Old Son said:

So you think the Aquadrive is worth the cost over my current setup?

If set up properly, and if checked periodically to see if the mounts have settled, no

We have an Aquadrive, it maked perfect sense in our boat when it was a hire boat. In such a boat, a tricky engine problem is fixed quickest by swapping the engine. If you don't have to align the propshaft it is faster to do

Richard

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2 minutes ago, RLWP said:

If set up properly, and if checked periodically to see if the mounts have settled, no

We have an Aquadrive, it maked perfect sense in our boat when it was a hire boat. In such a boat, a tricky engine problem is fixed quickest by swapping the engine. If you don't have to align the propshaft it is faster to do

Richard

And is it an easy job to check if mounts have settled? I remember I had the engine aligned about 4 years ago and it took the engineer over an hour.

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1 hour ago, Old Son said:

And is it an easy job to check if mounts have settled? I remember I had the engine aligned about 4 years ago and it took the engineer over an hour.

Whilst alignment is not critical, it is still essential that the mounts are set up and adjusted properly.  The worst thing is if the engine can rock on the diagonals;  the alignment can seem ok, but the engine could shake and quickly wreck the mounts.  Many "engineers" are woefully inadequate when it comes to setting up the engine mounts,  and it is essential that new mounts are checked after bedding in for a while.   An hour is not unreasonable for someone who knows what they are doing; of course, this is no guarantee that this is the case!

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Single element flexible drives like most Centaflex ones are only designed to accommodate a small amount of angular misalignment. If you want to deal with radial misalignment such as flexible engine mounts probably produce you need two points of flexibility but two points of flexibility  has the potential to allow the shaft to dogleg under thrust so a thrust bearing on the prop side of the joint is required. The Aquadrive, Pythondrive, and a long Cetaflex coupling allow this as will a pair of universal joints plus thrust bearing.

Not only do such setups avoid accurate shaft alignment issues they also prolong gland and bearing life by stopping the shaft sliding in and out of the boat as the thrust moves the engine on its mounts and keeps the shaft in more or less perfect alignment. All this has been mentioned above.

If a single element flexible coupling is fitted on a flexibly mounted engine then engine vibration gets transmitted down the shaft and any radial component bangs the shaft about in the stern bearing/shaft causing vibrations through the hull. A solidly mounted engine can not do this and on a setup with a flexible sterngland and Cutless shaft bearing(s) the compliance in the land and bearings may avoid the hull vibration issues.

In my view such drives should be all but standard with a flexibly mounted engine as long as it can be fitted into the space available. The difference they can make is very noticeable when boating. I have no real evidence but a very verbal reports indicates the Pythondrive MIGHT have a tendency to be more noisy but I can see no reason for it.

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Tony's post says it all but I would just add that the Python (and probably the Aquadrive) need to be slightly 'misaligned' - but not between the thrust bearing and the gland - I presume so that the innards of the CV joints work over larger wearing areas. This makes my sloppy engineering a virtue. As for protecting the engine / gearbox from stresses I would say that although the Python / Aquadrive is probably the best set up the one you have now is probably quite ok so long as its trouble free. Depends on budget and also note that you need a plate welded in the hull to bolt the unit to and enough length to fit it.  As for setting up engine mounts I re sat my engine this summer, took b**** hours.

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Thanks all. I am going to recheck measurements, speak with the engineer some more and then make a decision. I have received an article that dor wrote which is very informative and concise. It is well worth a read if you are considering this modification. I'll update what I do in due course and if I do go with this I'll let you know what I think.

Thank you to all who have provide advice and comments, its much appreciated.

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