Engine/Prop-shaft alignment

[Ken13559]

Now that I've recon the engine mounts and after watching a Youtube instructional video on engine/shaft alignment, I when ahead an get the alignment done. But somehow I still has this feeling that the alignment is not quite right. Vibrate seems alittle more than before I started this recon work but it is not terrible. Alignment wise is definitely better, meaning the gap difference between flange face is lesser. However, I do note that when the prop shaft is free from the gear coupling flange it droop down. There is about 1" of verticle play. When do the alignment, I just let the shaft droop down and set the engine mount height accordingly. Is this correct? Somehow I have this feeling that the shaft should be located centrally but that would means rising the gear coupling flange be about >1/2". That seems alot of adjustment. Any help and advise appreciated.

 

[Ralph Johnstone]

I Don't Really Know Why .................................

However, I do note that when the prop shaft is free from the gear coupling flange it droop down. There is about 1" of verticle play.

........................ but there's your problem. I can't see this being the cutless bearing as you would need about a foot of clearance in the bearing and I can't see the shaft log and attached hose allowing that much movement. A real mystery .

I can only suggest you haul the boat and see where the play originates.

 

[Ken13559]

Last haulout 1_1/2 months back, cutlass was ok. I think the droop in the prop shaft is normally as the only support there is the flexible hose clamped between the shaft-log and the packing-gland assembly. Question is, do I lift the shaft to say mid-way of the verticle play by raising the stern end of the engine?

 

[Ralph Johnstone]

If you are going to ignore the droop, then I would pick a vertical point half way between the upper and lower extremes of travel, support the shaft at this height, and then do the alignment.

I cannot overly stress that your shaft should not be freely flopping about under its own weight. The hose is very rigid, very short, and does not allow for easy movement. Try squeezing the hose with your fingers to see if it's rock solid ................... it should not deform at all.

 

[Ken13559]

Ahhh... I see, so if the hose is soft then its time for a replacement? I've not thought of that. I guess it'll need a haul-out if I want to replace the hose. Ok, so meantime, I should centralise the shaft and raise the engine accordingly. BTW, is this hose special for packing-gland or can I buy any rigid exhaust hose for this purpose? Thanks for the info.

 

[anchorclanker]

You do realize that that sloppy shaft is indicative of a major failure in the tube, cutlass bearing assembly, and that it could fail completely? Without warning? That it could flood your boat rapidly? Haul the boat as suggested and repair as needed. Once the shaft is assembled properly you can then align the engine to the shaft.

 

[Jared1048]

is the shaft resting on the hull? I had the same thing happen to me and I dove over the side to take a peak at what's going on and noticed my strut was broken! Get over the side with a mask and see that your strut is still in good condition.
There shouldn't be any major movement of the shaft. I think you have a more serious problem than it appears!

 

[Ken13559]

Now I'm worried. hmm, as best as I can tell, the P-bracket is ok, the shaft is not touching the hull, the hose is alittle "soft"..could be. Need to check. Thanks.

 

[rardiH36]

Ahhh... I see, so if the hose is soft then its time for a replacement? I've not thought of that. I guess it'll need a haul-out if I want to replace the hose. Ok, so meantime, I should centralise the shaft and raise the engine accordingly. BTW, is this hose special for packing-gland or can I buy any rigid exhaust hose for this purpose? Thanks for the info.

Included in the article by Maine Sail on stuffing box repair (url to it below) is a section about the stuffing box hose -- with pictures. Rigid exhaust hose isn't the right product.

http://www.pbase.com/mainecruising/stuffing_box.

 

[kloudie1]

The alignment is normally done with the shaft centered in the log. It is normal to have an inch or so of movement. The technique should start with centering the shaft in the motion range (up/down as well as left/right) and supporting it with a wood block or something else that works.. Then begin to align the engine to the shaft flange.

 

[Ken13559]

Rardi, read through Maine Sail article. Noted the Buck Algonquin hose.
Claude, I'll go with your suggested approach, though it means raising the engine quite abit.
BTW, would be near impossible to change the stuffing box hose on water? Just asking.

 

[boatertwo]

Providing the shaft seal hose is good, a little shaft droop is normal when the couplings are disconnected. Yours does not sound excessive. When aligning engine to shaft, join two halves of coupling together. If there is no shoulder on the inner rim of one half to mate with the other, put in two coupling bolts opposite each other and tighten finger tight so the coupling faces are just touching.

Now take your feeler gauges and check between the coupling faces at 12, 3, 6, and 9 o'clock with the smallest feeler guage. Using the other feeler gauges at these positions will tell you how much adjustment is required. For minimum vibration, your highest reading should not exceed .002-.003 thousandths of an inch. You can attain this by raising/lowering the front/rear of engine and/or moving front/rear of engine left or right. After adjustment, tighten the two coupling bolts and rotate the coupling by hand, loosen the two bolts and recheck your readings to see if additional adjustment is required. If there is no change, install the remaining bolts and tighten.

Before you seperate the couplings again, for maintenance, etc. punch mark each half opposite each other so they can be reinstalled in the same position.

 

[Ken13559]

Providing the shaft seal hose is good, a little shaft droop is normal when the couplings are disconnected. Yours does not sound excessive. When aligning engine to shaft, join two halves of coupling together. If there is no shoulder on the inner rim of one half to mate with the other, put in two coupling bolts opposite each other and tighten finger tight so the coupling faces are just touching.

Now take your feeler gauges and check between the coupling faces at 12, 3, 6, and 9 o'clock with the smallest feeler guage. Using the other feeler gauges at these positions will tell you how much adjustment is required. For minimum vibration, your highest reading should not exceed .002-.003 thousandths of an inch. You can attain this by raising/lowering the front/rear of engine and/or moving front/rear of engine left or right. After adjustment, tighten the two coupling bolts and rotate the coupling by hand, loosen the two bolts and recheck your readings to see if additional adjustment is required. If there is no change, install the remaining bolts and tighten.

Before you seperate the couplings again, for maintenance, etc. punch mark each half opposite each other so they can be reinstalled in the same position.

Noted. Thanks. That would be the approach I would take. There is a raised face/shoulder to the shaft side coupling that will sit in the hole of the gearbox flange. I'm still trying t overcome the "fear/concern" that I need to raise the engine by between 1/4" and 3/8". I suppose there could be some weakening of the 10 year old engine mount by now.
I'm also suspecting the Hose to be kinda "soft" as well. Yet to confirm. That would have to be a haulout job? Would it be very risky to replace the Hose while on water?

 

[anchorclanker]

I'm still trying t overcome the "fear/concern" that I need to raise the engine by between 1/4" and 3/8". I suppose there could be some weakening of the 10 year old engine mount by now.

I recently repaired a Mercruiser stern drive that had stripped its driveshaft splines. I had to raise the engine almost 7/16 inch to align it properly. It was a 20 year old boat, and mounts do continually settle. But most I have checked needed a good 1/4 inch raise to get them back inline.