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View Full Version : Shaft alignment on a V-drive


bigmac
05-10-2006, 09:18 AM
I've read Ken Gibbons' description of prop shaft alignment, but I wonder how the process changes on a V-drive. If anyone has ever checked or adjusted shaft alignment on a V-drive, I'd appreciate your insights.

Tom023
05-10-2006, 11:13 AM
Bigmac, I just went through the process of aligning mine this winter, twice, once with old cutlass bearings and once with new bearings. I read the article and it was very helpful in getting me started but I did not follow it exactly. Since I didn't quite understand the discussion about making sure the strut and engine were parallel, I essentially ignored those steps. What I determined is that the position of the shaft through the log is determined by the strut, and more specifically the cutlass bearings. So, as long as the shaft goes through the log without touching, it does not need to be exactly centered, the strut/bearings are in "good enough" position. The important part is really getting the engine/transmission aligned to the shaft so there is no binding when the two are coupled and the faces mate to within the .003" tolerance.

The other thing I did differently is that when checking the tolerance, I did so by mating the transmission and coupler without bolting the two together losely. I just slid the coupler together by hand very firmly so it was seated at one point (.000" clearance) and measured the gap all around, then rotated the coupler 90 degrees, measured, etc. I found if the bolts are used, it's possible to get the gap to within tolerance even with a misaligned engine. I posted this once before, but with my boat, my coupler when bolted was within the .003" tolerance even though it was out of alignment by 3/4".

I'm sure there are many variations and nuances to doing this procedure, I tried to keep it simple and logical and am very happy with the increase in smoothness as a result of a properly aligned drivetrain.

Also, on a V-drive, you will need a slide hammer to get the shaft out of the coupler (if you ever need to, not necessary for an alignment). The DD guys can use a socket to press it out, we are not as lucky.

bigmac
05-10-2006, 11:31 AM
Bigmac, I just went through the process of aligning mine this winter, twice, once with old cutlass bearings and once with new bearings. I read the article and it was very helpful in getting me started but I did not follow it exactly. Since I didn't quite understand the discussion about making sure the strut and engine were parallel, I essentially ignored those steps. What I determined is that the position of the shaft through the log is determined by the strut, and more specifically the cutlass bearings. So, as long as the shaft goes through the log without touching, it does not need to be exactly centered, the strut/bearings are in "good enough" position. The important part is really getting the engine/transmission aligned to the shaft so there is no binding when the two are coupled and the faces mate to within the .003" tolerance.

The other thing I did differently is that when checking the tolerance, I did so by mating the transmission and coupler without bolting the two together losely. I just slid the coupler together by hand very firmly so it was seated at one point (.000" clearance) and measured the gap all around, then rotated the coupler 90 degrees, measured, etc. I found if the bolts are used, it's possible to get the gap to within tolerance even with a misaligned engine. I posted this once before, but with my boat, my coupler when bolted was within the .003" tolerance even though it was out of alignment by 3/4".

I'm sure there are many variations and nuances to doing this procedure, I tried to keep it simple and logical and am very happy with the increase in smoothness as a result of a properly aligned drivetrain.

Also, on a V-drive, you will need a slide hammer to get the shaft out of the coupler. The DD guys can use a socket to press it out, we are not as lucky.Great info, Tom, thanks. I'm a little fuzzy on the details, but hopefully will be able to puzzle it out once I get into it.

Right now, I have more vibration in the drive line than I think I should have, but I don't know if it's the OJ cast prop or shaft alignment. I'm suspicious of the latter since hand-turning the prop is a two-hand job, but I'm new to inboards and I'm not really clear on how much tension there should normally be at the strut bushing. OTOH, it's pretty smooth up to about 30 mph going straight with increased vibration when I turn right. Speeds above 30 get increasingly noisy and top speed (46) with a right turn gets downright raucous.

I did have the dealer do the alignment at the 20 hour check last year, but I'm not totally sure of the job they did. As was mentioned in the article, it's a tedious enough job that one wonders at what point the service tech says "good enough"...

Tom023
05-10-2006, 11:40 AM
Turning my prop was a two hand job, and right now it still takes a firm one hand, but my cutlass bearings and shaft seal are all brand new and are tight, so we'll see if it loosens up. I know for a fact my engine/shaft are in perfect alignment because I took a long time to get it right and managed to get to .001. The reason why I did it, instead of my dealer, is because the service manager said they don't worry about the .003" tolerance, they just get it to where the coupler slides into the transmission without binding, and call it good enough. I learned a lot about the drivetrain doing it myself and am glad I did. If you have any questions I can talk you through what I did.

wakescene
05-10-2006, 02:41 PM
bigmac,
Tom's advice on the aligning up the shaft without connecting the coupler is perfect. This is what I did last year. Set everything up, then adjust the mounts till the tolerence is within the recommended.

when it's all said and done, you should be able to turn the shaft with one hand directly on the shaft, not the prop. (prop give you leverage). But like Tom said, if your equipment is new, it might be a little tight at first.

I'd also recommend a good set of pry-bars, WD-40 and a large rubber mallet for the job, they will help tremendoursly when trying to move a several hundred pound motor/tranny setup.

GL,
KG