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Old 08-06-2009, 08:03   #1
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Drivesaver - Good or Bad ?

I am looking for experience of those that have used a drivesaver on their boats. I recently hit a submerged log and had to have tranny rebuilt. My searches have shown that they are not effective for low rpm sailboats and that it does not really help with alignment. A drivesaver for those not familiar is a plastic disk on the drive shaft separating the transmission from the drive shaft that is supposed to give in the event of hitting something with the prop.
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Old 09-06-2009, 08:18   #2
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I personally prefer the flex coupling made by R&D but the Drivesaver works almost as well. We supply one with each small engine that we sell and they basically serve three different functions;
1) they are a barely flexible coupling so wont make up for a misaligned engine but they do soften the shock of immediate gear engagement.
2) they break the electrical connection between the engine/transmission and the shaft and prop. This lets the zinc on the shaft look after the shaft and prop only and
3) they are the fuse (weak link) in the system. We did have one customer who caught a heavy line around his prop and he destroyed his flex coupling. His transmission was fine and the engine stayed secured the engine beds. This was on a Catalina 30.
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Stanley
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Old 09-06-2009, 09:44   #3
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Aquadrive - The System goes one step further, and will make the engine vibration to boat, and alignment concerns a thing of the past.
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Old 09-06-2009, 11:20   #4
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While the Aquadrive system is great as far as alignment is concerned but it does not offer the break away feature that Ewingengr has asked about. It is also expensive and requires a lot of engineering to retrofit into any boat whereas the R&D coupling or Drivesaver can often be fitted without any modification at all.
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Old 09-06-2009, 11:34   #5
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Yes, I checked the link and not only does it look expensive I don't have the "real estate" for it. Primary purpose: save transmission, secondary would be alignment. Any users out there????
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Old 11-06-2009, 08:13   #6
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I have put an R&D coupling on every boat I have had. It just makes sense to me. Going on my latest boat next week.

I like the "bit of give", the isolation, and the breakaway/shock reduction. I have used it on a boat where the prop shaft was too short to get on a zinc too, and when the end of the shaft needed to be cut off as it had seized in the coupling. Great value for money in my opinion.

The whole principle of sailboat engine mounting seems wrong to me, with the mounts taking the thrust. The aquadrive would be my first choice, but it does require a lot of space and a bulkhead to take the thrust. I have never tried it though
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Old 11-06-2009, 08:31   #7
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I used to use them. They destroyed themselves too easily making for an unreliable drive train.
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Old 11-06-2009, 09:57   #8
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I had one try to sink my boat 600 miles from anywhere last Fall on my way to Tortola. I had one installed when I added a Maxprop 4 years ago as I needed the shaft to be slightly longer. Un-noticed by me the nuts on the drive saver had slowly backed off over the years.These were lock nuts with plastic inserts. When we had to start the engine when a halyard broke, when the engine was put in gear all the bolts sheared and the shaft dropped down, misalligning the Lasdrop allowing water to pour in. Luckily, the leak was controlled with a Spanish windlass that realligned the shaft and we were able to sail all the way into Village Cay Marina without further problem where we replaced the drive saver.
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Old 11-06-2009, 10:30   #9
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This sounds like a very good reason to not only use a regular stuffing box instead of a dripless seal, but also to occasionally go around your engine installation and make sure that things are tight. You must have had some vibration to cause the nylock nuts to loosen as they dont do that on their own.
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Old 11-06-2009, 11:28   #10
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This is the information I was looking for. I sail in Chesapeake now where there seems to a lot of flotsam and jetsam. When weighing the cost of a rebuilt transmission I will take my chances with loose bolts and drive saver self destructs. I looked at R&D website, and found some at GO2marine made by PYI. Where the bolts came loose did you do the installation or somebody else?
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Old 11-06-2009, 11:38   #11
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I don't think they remove the need to align the shaft and engine. They are probably more forgiving of poor alignment, but they would be working much harder.
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Old 17-09-2010, 09:00   #12
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Do any of the members have the data on how thick the PYI coupling is?
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Old 17-09-2010, 10:49   #13
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Even though this thread is over a year old, I think the OP's last sentence about the purpose of a Drive saver contain a popular mis-conception IMHO.
I have never believed that this device has a "safety-shear" function.
It does not substitute for correct alignment, but does absorb torque shock from Transmissiuon to shaft.
Likewise, correctly installed, I think it very unlikely that they can fail as a connection.
Mine has high grade, fine thread, Allen screws recessed into the disc, connecting to the engine coupling. These, when correctly torqued have their head end flush with the shaft flange mating surface, and cannot back out.
The shaft coupling is held to the disc with Fine thread cap screws and Ny-locs and flat washers to prevent any elastic movement of the synthetic disc being passed to the nuts.
I have never had a problem with this arrangement.
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Old 26-11-2011, 09:28   #14
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Re: Drivesaver - Good or Bad ?

I have used drivesavers for over 20 years and have never had a problem with them. They stll require you to line up the engine accurately (although the specs give you +/- .010 on angular on a sx inch coupling) The main advantage I have found is reduced vibration transmittal (in both directions, engine to hull though shaft does happen). They also reduce shock loads on the tranny and provide the electrical decoupling, which is important if your stuffing box doesnt provide a ground to the shaft. I had one case I saw where a poorly grounded boat was using the shaft as the ground, and after an electrical problem, ended up with both pitted bearings in the transmission and a prop made of bronze foam, or swiss cheese if you prefer.
I wouldn't do a new installation without one personally.
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Old 26-11-2011, 12:12   #15
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Re: Drivesaver - Good or Bad ?

My experience with Drivesaver is much the same as Blue Stocking and dglaab. 21 years ago I rebuilt a 4108 Perkins and installed it with a drivesaver because it added enough length to the shaft to put a zinc in front of the prop. I removed all bonding from the boat at the same time and the shaft zinc stands alone as electrolysys protection. The zinc is replaced every six months during a divers inspection and still looks good. The drive system operates smoothly and without vibration and the shaft shows no sign of wear or deteriorizing, I did replace the prop this year, it looks fine but I just didn't trust it anymore. I kept it for a spare though, Damn but props have gotten $pendy over the years. Jesse
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