In water shaft alignment questions

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Hey guys,
So most of my major issues with my Silverton have been addressed. But I am having reoccurring problems with the shaft staying in place. I want to align the engine to the shaft. I am confused as to how you know what position the shaft should be in. There is some play in it when the coupler is unbolted. A lot less when the packing nut is tight, but still some. I dont really get how you know the shaft is in the proper position to start moving the engine around.
 
I haven't had need to do that yet but here are a couple interesting relevant articles:

(This is for a ski boat, but the general principle is the same:)
OK, sorry that link didn't translate well , but you can Google search "inboard shaft alignment " and find the document, "Propshaft Alignment - Mastercraft" .

And from marine surveyor Dave Pascoe: http://www.yachtsurvey.com/Alignment2.htm
 
Thanks, Bill. I noticed that when I checked right away and was editing while you posted.
 
When I worked on large boats, we did the final alignment after the boat was in the water for a few hours. Days in the case of a Wood boat.
I'm not sure what you question is, but we used Feeler gauges, and got the Gap to within .003 before bolting it up solid.
 
You are adjusting the engine mounts so that the face of the shaft flange is nearly parallel to the face of the engine flange.
Loosen the flange attachment bolts so that you can gain a slight gap between each of the flange faces.
If you remove the bolts completely mark each flange first to be able to bring them back to the same holes if they become mixed.
Using longer type (valve) feeler gages measure the gap around the flanges at each quadrant - like a clocks positions midnight, 3, 6 & 9 O'clock.
You are aiming to have the gaps be at or less than 0.001" for every inch of flange diameter - so a 5" wide flange would have a gap difference goal or 0.005".
After adjusting the engine mounts to be within this limit rotate the entire shaft 90 degrees and recheck the gaps at each quadrant. Repeat for the remaining two quadrants.
If you suspect any chance of a damaged or bent shaft do this last step before spending too much time aligning mounts to look for major differences in rotational gaps.

Please note you will need to completely tighten the engine mounts bolts each time to be able to measure the gaps with repeatability. If you have any issues with cutlass bearings, trans output bearings or engine mounts themselves they need to be dealt with before attempting alignment.

Hope this helps
 
The cutlass bearings are new, the shafts have been true'ed. I found last night the engine mounts bolts to the stringers are loose, and have to finish that first.
My main question in knowing how the shaft position should be. Articles I read said to center it in the shaft log. When it is in the water, not so easy to just undo the packing nut, center it, hold it there, then align the engine to it. It seemed when I was putting in the shaft that there is not much space around the shaft in between the log, but you can move the shaft around in the log a bit when it is not bolted to the tranny.
Must be I am overthinking it and just need to pull it up close to trans flange and start the feeler gauge testing?
 
I think you are asking how to center the shaft before you begin bolting to the coupler, and not how to do the actual alignment with the feeler gauge?
 
The goal is to take the shaft log out of the equation as it needs to align with the shaft not the other way around.
If the log was working before the alignment and untouched you typically ignore it for the most part as the hose is somewhat flexible and the increment of adjustment are very small.
If you had a shaft log completely out and replacing hoses and packing the boat is on the hard and you align (preliminary) the shaft to the engine without hard fastening the shaft log hose or packing , then attached the shaft log aligning it best way to the existing shaft.
When the boat is back in the water for a couple of days you can complete the shaft alignment with the hull relaxed.

The shaft packing is dependent upon the shaft alignment and should 'float' around the shaft with the least interference.

Hope this helps
 
Assuming the shaft is aligned within the struts and cutlass bearings (this defines the centerline for the entire shaft/gear/engine asembly). Then slide the shaft towards the engine and lift the shaft at the flange to estimate how much droop is caused by the weight of the flange and free shaft. Then try to support shaft vertically in what would be the unweighted straight shaft position. Then move engine to best lateral and vertical position so gear output flange to shaft flanges are as centered as possible. Depending on the actual shape of the flanges you may be able to use a straight edge or angle to better estimate or eyeball the gear/engine centerline to the shaft centerline. Once the centerlines are close, then use the feeler gauge method to make the faces of the flanges parallel as described above. But note that moving the engine at the front mounts (pivoting on the rear mounts) may be preferable for making the flanges parallel due to the geometrical movements.
 
An old school of thought was you needed to put lifting tension on the shaft at the engine end equal to half the weight of the shaft.

If your shaft is loose in the bearings than you need new bearings.
 
My Crusader manual says to move the uncoupled shaft to the limits, up, down, then right and left, then back to the center of the log.
 
My posts assume this is a standard 37 gas powered Silverton with new cutlass bearings and 1-1/4" shafts which have existing flanges reasonably inline and containing flange 'lips' which are engaged when the shaft flange is introduced to the trans flange.
Aligning a removed strut or engine mount bed when it has been removed or damaged is a much larger undertaking which I have unfortunately done as well - much to my huge underestimation at the time.

Hope this helps
 
the coupler end of the shaft will sag since there's no support without it being attached to the transmission. insert the coupler bolts but don't tighten the nuts. the faces of the couplers need to be very close to be accurate.
 
Thanks guys, that is helpful info. I will be checking it later this evening. The shafts are 1 and 1/2 inch. New coupler, engine did not move, the shaft had been bent and is now straight. What I did not do carefully was check the strut for straightness. Hoping that the shaft wobble will go away once everything is tight and the engine alignment is good.
This a boat I have only owned for a couple months and was obviously grounded by the previous owners, in case anyone did not read the previous back history on my woes of this vessel.
 
I would think it is important that the shaft should run concentric to the engine shaft(Flange)after all bolts are tight.
Checking concentricity of prop shsft to engine flange could be done using a dial indicator and turning the shaft by hand.
The previous step is probably unnessesary if both flanges have nesting capability machined into them.
 
The flanges did have the nesting capability in them, so it was easy to see that the alignment was out once I got all the engine mounts to stringers tight. I had to move the engine to port a bit, and adjust the height. The outcome was good, it came in right around 3 thousands. Then we took it out the next day, last Saturday, and the shaft spins true finally. Hoping this issue is behind me for good at this point. Thanks for all the advice.
 
The sneaky way to know you have your shaft aligned to the cutless is to turn the shaft. When centered it will turn easy. If this spot is not dead center in the stern tube, the cutless alignment is likely off.
 
Just be sure to loosen your pack gland before you try to turn the shaft.
 
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