Engine Alignment Question

[Fish 0]

Its interesting that the boatbuilder says to do all that out of the water, 

I've always understood the fine tune has to be done in the water. I can understand from a boat builders perspective though, you need to get it as good as you can before launching, substantially simplifies the fine tune.

 

I'm just contemplating how easy this job would be if I could get the flanges together. I would see the point of accounting for the shaft weight and drop then, I'd be able to measure stuff accurately and easily...

[Island Time 1,220]

all agreed, but if you remove the stuffing box and wedge the shaft, you are going to get a fair bit of water into the boat - this can take a few hours!

[Island Time 1,220]

How do you know its in the centre of the tube if you dont  move the stuffing box??

[Fish 0]

How did that all work for vibration lateral?

Assuming the extent of your rebuild you used new engine mounts, what about the drive damper plate?

And do you use a flexi coupling?

[Fish 0]

What gearbox ratio do you have, 2.3 / 2.6?

I'm interested in the shaft speed compared to mine, I expect they'd be similar.

[Island Time 1,220]

Shaft speed should be around 1400 rpm....

[harrytom 642]

Fitted a dripless seal,shaft was slightly out align but no vibration until barnicles on prop or zinc block worn,16hp yanmar ran at 3/4 most of the time

[wheels 543]

I just took a brief look over the replies here and will try and cover the questions.
For a single bearing/stuffing box design, the alignment is less critical than one that has a P strut. In fact it would be difficult to have the engine out of align enough to cause an issue, unless something was seriously wrong, when it comes to a single bearing install.
If you have two bearings, then alignment is a lot more critical. Or you can damage the shaft, bearing, stuff box and binding can cause vibration.
The closer to perfect alignment the better, however, it is not essential and a misalignment of up to 1.5mm is still OK. So most of us aligning a shaft would likely get it much closer than this. As already said, the amount of movement an engine has on mounts is astonishing.
With a shaft unconnected, i move it side to side and up and down and measure the points at which the movement stops. I place a piece of timber under the shaft and wedge it to get the shaft to the vertical centre point, then move it side to side and clamp it at the horizontal centre point. That should get you pretty damn close to centre. Then you align the engine/gearbox to meet the shaft.
 

[vic008 17]

My 2 bobs worth- like thee volvo sea instead of the pricey non drip( google yachting boating world forum)

Also how on earth can you load up 4 engine mounts equally? Three yes, but 4 is just guesswork for the last one. Adjust number 3 good but it takes all the weight and leaves nothing for number 4 to take.

[wheels 543]

My 2 bobs worth- like thee volvo sea instead of the pricey non drip( google yachting boating world forum)

Also how on earth can you load up 4 engine mounts equally? Three yes, but 4 is just guesswork for the last one. Adjust number 3 good but it takes all the weight and leaves nothing for number 4 to take.

 

Just slightly unclear about your post.

You need to keep the engine mounts all close to the same load shared across all of them. Easy to do. Measure the thread on each. If the engine is slanted down, the mounts are usually fitted as such. Cross ways, the mounts will be the same heights, but there could be small variances longitudinally.

[Myjane 40]

Usually gauge them to 5 thou ish all round ,I did my own and the engine room offered advice to help out ,