Engine Alignment

[boden36]

If you have room for it I would heartily recommend a short length of shaft with a CV joint at each end. You will also need a thrust bearing. Scatra made the one on our boat which has been great for many years. With this set up you really only have to get the alignment approximate. Also makes for a quieter boat when motoring. Regards, Richard.

[Talbot]

Originally Posted by boden36

If you have room for it I would heartily recommend a short length of shaft with a CV joint at each end. You will also need a thrust bearing. Scatra made the one on our boat which has been great for many years. With this set up you really only have to get the alignment approximate. Also makes for a quieter boat when motoring. Regards, Richard.

Trouble with that solution is that it does not do anything to cope with the thrust from the prop pushing the engine forward onto the stops on the mountings, and thus transmitting most of the vibration to the hull

Suggest you consider:

Aquadrive Vibration Control Couplings



.

[Cheechako]

Yea, I'm really surprised a plain old U joint isnt used more often. Maybe a lot of boats dont have the room, maybe they dont work well unless you have two (a driveshaft) to deal with the movement of the engine on the mounts....

[Talbot]

Universal joints are fine as far as resolving misalignment. They worsen the problem of thrust unless you have some form of thrust bracket - which is what the Aquadrive provides.

[sailingmonica]

We had similar problems, our engine mounts broke as a result of the shaft flange key being one size smaller than the groove, which eventually caused the shaft to vibrate and rotate a tiny bit every time the gears were engaged and eventually vibration ruined the mounts, which further increased the vibration. We were in St Augustine, FL at the time we discovered what the problem was and the locat boat yards were determined to cover their quarterly revenue from our wallet, so we decided to replace the existing classic flange system with the Aquadrive system, which uses a thrust bearing and a CV joint. We were able to install it ourselves, in the water, in about five hours. A year and a half later, we are still very happy with it. Take a look at Aquadrive here www.aquadrive.net.

[boden36]

Talbot, a CV joint set up is incapable of handling thrust. These units have a thrust bearing mounted on a hull bracket at the inside end of the prop shaft.No thrust gets to the engine. The system minimises vibration and noise. We have run it for over 20 years now and wouldn't consider anything else. Regards, Richard.

[harmony80]

Thanks everyone for your referral to Pringle...greatly appreciated.
Harmony

[s/v Jedi]

The Aquadrive is lovely (we have it) but it's just a thrust bearing and cv joints. I think the thrust bearing is the best part of it, a way smarter way of coupling prop to hull.

cheers,
Nick.

[danhaun]

Originally Posted by ribbony

No, you do not need to do it other than engine off, at rest in the boat, preferably in the water, not on the hard stand or slipway. What the goal is here, is to have the alignment to a close tolerance without any sideways stretch of the rubber in the engine mounts.

If you have your engine bolted down to the engine beds via the engine mounts and check you tolerance, noticed it was out in the lateral alignment (vertical adjustments are much easier), and needed to make an adjustment. Then you need to move the motor sideways to get the tolerance to specification. However, all bolts holding the engine to the beds need to be loosened so any adjustment is made by moving the entire engine, left, right etc. If you move just one mount then you will have some sideways pressure on the shockabsorbing material of the other mounts, if you bolt down the motor then that residual tension can cause the engine to assume a slightly different position after the first use or while under load. The engineer who told me of the best approach did it with gear a bit too complex for me to worry about, he used a lifter that sat in the vessel with an arm that came over the engine and had 4 sling to above each of the engine mounts, the rig could be adjusted in any direction so the engine could be positioned laterally for alignment with minimal pressure on the mounts. Then when the lateral position is found the engine is lowered on the beds, fastened and the vertical adjustments done along with any fine tuning of the lateral tolerance (if needed).

Hope that helps, bit hard in this case to use words to describe a manual skill.

I found this hint on the web somewhere and it might be a solution to the problem of horizontal alignment. Put a deflated basketball under the engine and inflate slightly to allow easy left right movement.
Sounded like the right idea to me but I have not yet tried it.