Engine Alignment Question

[Briankinley2004]

Replaced all three cutless bearings on my port side and splashed Friday. Decided to check the alignment this afternoon as I read it is best to do this in the water. Got the coupling unbolted and there was at least a .020" difference between the gap at the top of the coupling and the bottom. It seemed to be a uniform transition and the side measurements were close to the same. I dropped the front mounts about a 1/4 turn at a time until I got to the measurements in the picture below. This is facing the back of the engine looking forward. It seems the "right" side tightened up slightly more than the top and the "left" side is tightening up about like the bottom. Im trying to follow the geometry to figure out which mount I need to lower a bit more to get this right but I have hit a brain warp. Any of you folks with experience with this kind of work have any recommendations?

 

[Boatsb]

Check the location of the shaft in the stern tube first. If in line then the rest of the measurements will work out. The coupler weight will put a slight drop in the shaft when it's not supported.

Also the side to side will require movement laterally if the mounts allow it.

 

[Briankinley2004]

Check the location of the shaft in the stern tube first. If in line then the rest of the measurements will work out. The coupler weight will put a slight drop in the shaft when it's not supported.

Also the side to side will require movement laterally if the mounts allow it.

It looked centered from behind when she was out of the water. Sort of hard to tell anything inside the boat as the hose is over the tube and the packing box is in the hose. I think the coupling is still supported by the transmission plate so there is no sag. It is resting on the mating part on the center of the transmission plate. The measurements are the actual feeler gauge readings not the differences in distances

 

[whoover]

If my memory serves me from my power transmission millwright days it looks like the front of the engine needs to move .003" to the left while not letting the back move and raise the back .003".

Walt Hoover

 

[Briankinley2004]

I was curious if I should be raising the back instead of lowering the front. Or splitting the vertical movement equally between the 4 mounts. I have adjusted the front down approx 2 complete turns of the nuts and haven’t touched the back

 

[sparky66]

You need to cock the engine to get that in alignment. Essentially lower the right front mount and raise the left rear, or do the opposite. How long has the boat been in the water? You will want to wait a few days after launching to do this adjustment.

 

[Briankinley2004]

You need to cock the engine to get that in alignment. Essentially lower the right front mount and raise the left rear, or do the opposite. How long has the boat been in the water? You will want to wait a few days after launching to do this adjustment.

Will try that. It has been in the water for 3 full days now

 

[cww]

This is something I would let the marina do, it's a tedious job. But that's just me. I know some people really insist on doing it themselves and I respect that. With that said, the marina has a laser sight gauge for this purpose that seems to deliver a better result. Whether you could make something like it with a laser level and something to use as targets, is an almost certain yes. But with technology having advanced that far I have never seen the point in trial and error. Had to go through this when I discovered I couldn't turn either of my props by hand (or even with a towel and a 2x4") when I was chasing a stalling when shifting problem at idle. I can attest firsthand that if the alignment's far enough out, your engines will stall going into gear.

 

[Briankinley2004]

CWW I wish that was something our marina could do. They don't have much technology like that and my understanding is the laser part is done before the shaft goes in to check the struts. I went back down to the boat and tried Sparky's method. While it got the top and bottom the same I still have a .006" difference from left side to right side. Cocking the engine didn't seem to help this doing the mounts per Sparky. Maybe I need to do something bass ackwards of that. Anyway some of the articles I have read on this say the tolerance is .001" per inch of coupling face. With my 7" face that would be .007" which means I am in spec. However I have read other things that say it should not exceed .005" Sliding the engine over per Walt makes the most sense to me however my mounts do not have any slots in them that I can find. Debating whether to leave alone like it is or figure out what to do. I could probably call someone in but they would pretty much be doing feeler gauges I am afraid.

 

[sparky66]

Just to make sure this is an alignment issue at this point, I assume that you take the same measurement and get the same results if you rotate the shaft to at least 4 different positions. As it stands now, it does look like you need to slide the front to the left or the back to the right. Are the mount holes bigger than the studs to allow a little side-to-side movement?

 

[Captain Ralph]

As sparky66 mentioned, a proper shaft alignment includes twisting the shaft 90° and measuring again.
I used to place a 0.010 shim under one bolt then measure all points while rotating the shaft. Then twist the shaft 90° to the flange and do it again, again, again.
This proves no deflection in the coupling or shaft.
Position the coupler to the flange in position that offered the most common measurements from the above test.
Then, align your engine.
I'll have to dig, somewhere there is this long and most correct way to align your engine/shafts.
It takes a few extra house and most yards do not do this.
Also, done after the boat has been in the water a few days including a run or two.

It does just take a fraction of nut turns to bring alignment back in. FRACTIONS OF TURNS...

 

[Captain Ralph]

Next, your numbers are in spec. What started this rat trap? If you think you have an alignment issue, Re-Read post # 11.

 

[Briankinley2004]

Ralph. I changed all 3 cutless bearings on port side and heard you should check alignment after a shaft comes out. I did not replace the shaft but had it checked at General Propellor. Anyway when I first checked it I was getting .040" at the bottom and less than .020" at the top. This remained constant when I rotated the transmission flange and checked at 180 degrees. I will post below my final results. I am glad to hear I am in spec as I don't think my original numbers where. At .001" per difference per inch of coupling face I would have needed a 20" coupling or more to be in spec.

Ralph is this the article you are looking for?

https://stevedmarineconsulting.com/wp-content/uploads/2021/04/TaskSheet190-EngineAlignment-05.pdf

 

[Briankinley2004]

Sparky - I did check at 1/4 rotations of the transmission flange. The difference was .001" at the most. In the drawing below the first numbers are what I got after I first measured after checking 1/4's today. After that I loosened all of the motor mounts except the back starboard side and tried to pry the motor over to port hoping there was a little slack in the mounting holes somewhere. I did not notice any movement on the mounts and the paint didn't seem to crack. I went ahead and checked anyway and the numbers read better ( .005" difference). I rotated 180 degrees and checked again and only one number changed by .001". This is the bottom drawing in the photo. I am thinking the vertical studs in my mount are leaning in their rubber boot now. If so I doubt these numbers stay but Ralph agrees the .007" is in spec so I am bolting her up and going for a run this weekend.

 

[dsharp]

You need to move the front of the engine inboard or the rear out board. Tighten the inboard rear mount so both ends don’t move. Put pressure on the outboard front and bump the inside front engine bed with a drilling hammer and the engine will slowly move inboard. The bottom holes on the motor mount should be slotted. Once you get your side to side set, lower the front until you tighten up the gap in the bottom. You want to shoot for no more than .003. It’s a 2 man job to move the engine over. If you just try to pry it over it always seems to go over too far. You don’t need to move it much. Pull the coupling together tight on a .008” feeler gauge on the bottom. Then check all your quarters with a .010”. If it won’t go in anywhere you have it within .002”. It’s pretty hard to get it closer without sending the coupling and shaft to a machine shop and having the coupling faced. I always left the gap, if any, on the top since the engine will settle in the rear over time. I hope this makes sense. Sorry, I just read that you were bolting it up.

 

[Briankinley2004]

Mr. Sharp - yes I read this after I bolted up lol. I did not see any slots in any of the mounting brackets, motor mounts or holes. I loosened the two bolts on each motor mount except the inboard rear as you said. When I tried moving nothing moved visually. I think the vertical posts look angled now on the front. I am going to go back and pull one of the engine mount bolts out just to make sure it is not slotted but if they were it should have moved. FWIW I did send the shaft and coupling off to the shop and they checked the tapered fit of the coupling to the shaft. They did say the shaft was out 11 thousandths at the engine end whatever that means. They said I could probably get a couple more years out of it but might have a slight vibration. I am going to try running it and see how she does.

 

[Captain Ralph]

I found it on line.

https://www.marinegears.com/pdf/GetInLine.pdf

 

[dsharp]

If the mounts aren’t slotted about the only thing you can do is break out the rat tailed file. That’s a suk job but it’s that or re-bed the strut and I’m pretty sure you don’t want to go down that road. I don’t really understand the coupling being out .011” unless they faced the coupling while it was on the shaft. From reading your post it seemed like your clearance’s stayed consistent when you rotated your shaft and re-checked. On the good side a dinged wheel will vibrate a lot more than an engine that’s not perfectly aligned. Get it as close as you can and bolt it up. Take care - David

 

[Briankinley2004]

Thanks David. It said the shaft was out 11 thousand and the engine end and 15 thousandth at the propellor end. Im not sure if that means the coupling or if the shaft is not straight? It slid right in the cutless bearings once I put a little soap in them

 

[doc g]

I would assume that the shop is saying the shaft is NOT straight and that there is an 11 thousandth run out at the coupling end and 15/1000 at the prop end. So I think you will not be able to get the alignment at he coupling in spec. Why didn't they straighten the shaft when they had it in the shop?? ................PAT