Propshaft Alignment: Near Portsmouth

[langstonelayabout]

After fitting my new Yanmar 1GM10 engine I'm having problems aligning it to the existing propshaft. A complete pain, after all, why won't it fit when its the same as the old one...

Does anyone know a reputable person/business that could align the engine and shaft? The new engine is in, all plumbed in and ready to go, just lacking alignment with the propshaft (blimmin thing).

Many thanks in advance

 

[Tranona]

Not a difficult job if you go about it methodically. If you have just replaced the engine withe same type the only reason for it to be out is the adjustment on the mounts.

 

[Birdseye]

I assume the boat is out of the water. If so try this approach:

1/ remove shaft seal and insert an old cutlass bearing into the engine end of the stern tube
2/ slide in the shaft until it touches the coupling which is still bolted to the gearbox
3/ slacken off the engine mounts and slide the engine sideways until its in line with the shaft. Try to get all the (soft) engine mounts in column ie not twisted not leaning. the bolts finger tight
4/ adjust the height of the engine mounts until the shaft will slide into the coupling. Make sure that each mount has the same number of visible threads side to side
5/ now tighten the coupling on the shaft but at the same time disconnect it from the gearbox. At this stage you have the engine near enough in line laterally and vertically ( any small isalignment can be taken up when the stern gland is fitted) but you havent got it in line axially.
6/ the easiest way of doing the rest is with a slip guage and you can make one. However use feeler guages and measure the distance between gearbox flange and coupling flange at 4 points at 90 degrees.
7/ First stage is to deal with the 3 o'clock and 9 o'clock differences by gently moving the egine and mounts. If you measure the distance from the rear mount to the coupling and then from the front mount to the coupling you will get an idea of the ratio of movement. Say the front is 3 times the distance of the back and you need to move the engine a bit to port because the gap on the port side of the flanges is bigger than the gap on stbd. Then you try to move the back mounts one third of the distance you move the front ones.
8/ Fiddle around with this until you are less that 1 thou out. In the going its important to make sure that the mounts are vertical and not twisted.
9/ Tighten the bolts at the feet of the mounts enough to stop them moving and adjust the height of the mounts remembering the ratio. Count the turns on the nuts.
10/ tighten the nuts and recheck the lateral alignment. If OK remove the old cutlass bearing and fit the stern gland
11/ dont be too fussy at this stage. All boats change shape on the hard so you will have a final bit of adjustment to do once in the water. Likely up / down. Do this by slackening off the coupling / gearbox flange joint and measuring the gap as in 7/ above.