What is being aligned, the engine, or the bearing, or both? And why?

[babikov]

I am replacing the gimbal bearing on my Alpha 1 Gen 2 outdrive of the Mercruiser engine. The old bearing and the seal are out. I wiped off the old grease in the bore and I just looked into it, and I have impression that the engine may not be properly aligned relative to the bore axis. This may be just an impression, since I did not measure anything.

I plan purchasing the tool and checking alignment after the bearing is inserted (new bearing is still out), but my main question is this: Does the alignment process concerns the position of the shaft (or the tool) relative to the bore axis, or it does not matter? Is it somehow measured or adjustred?

I am asking because I learned that the gimbal bearing itself is capable of rotating in its outermost shell quite a bit. Then, it seems possible to have the bearing and the engine perfectly aligned one with respect to another, but both be misaligned relative to the bore axis. Would that be a concern?

If both the engine and the bearing can be twisted, is it a priority to keep the bearing as flat as possible, reaching the desired level of alignment by twisting the engine? And, if the bearing is not in a perfect flat position (I assume it will never be) does it cause a premature failure etc.?

Thanks!

 

[CaptRedBR]

The bearing will be flat if you drive it in all the way. You will need to align the engine using the front engine mount. My adjustment nut was seized on and I had to cut it off. In order to reach the nut I had to remove the rear seats and panel in front of the engine. Don’t force the alignment tool, it can be difficult to get out if your alignment is off and you force it.

 

[babikov]

CaptRedBR,

I think you misunderstood me. Please watch the last part of this video:

It appears that for the gimbal bearing to be 100% flat, the probability is near zero. The outer case of it, yes, of course, if pressed far enough it will be perfectly flat (if not, it will not go into the bore, I think). But not the bearing itself.

Then my question is, if the bearing is so flexible, why to align anything? And when the bearing is aligned with the engine, they may still remain misaligned with the axis of the bore. How much of that misalignment is permissible, I wonder?

I did not do anything to the engine, so, if the bearing is replaced, the engine does not have to be aligned. All that is probably needed is to twist the bearing enough (basically by hands and the bar, like in that video) to direct the bearing towards the engine coupler.

What I want from the forum is to confirm that my understanding is correct (or, if not, then suggest another way of looking at it).

Thanks!

 

[dubs283]

it seems possible to have the bearing and the engine perfectly aligned one with respect to another, but both be misaligned relative to the bore axis.

no, you are not informed correctly or you are misunderstanding the given information

the outside portion of the bearing assy is press fit into the shouldered portion of the gimbal housing. it cannot move in any direction once installed

the center portion or inner race is the part of the bearing that is able to rotate/pivot on an axis fore and aft to a certain degree with a circular direction. the rounded design of the inner race that contacts the rollers allows for this to happen, hence the term gimbal bearing. this can be observed by installing the alignment bar into the bearing but not the coupler and rotating the bar in a circular motion

the rear engine mounts hold the aft portion of the engine in line with the inner race of the bearing, its the forward mounts that are adjustable up/down that allow for the angle of the fore/aft line of the coupler to be aligned with the inner race

if you unable to align the engine up/down to properly insert the alignment bar then the issue could be transom/stringer rot, faulty rear mount(s), incorrectly installed/damaged gimbal housing or inner transom plate

 

[achris]

.... Then, it seems possible to have the bearing and the engine perfectly aligned one with respect to another, but both be misaligned relative to the bore axis. Would that be a concern?

Yes, that's completely possible, but that would mean the rear mountings are 'off square', or the transom isn't flat and parallel (could be caused by rotting). It would show on the alignment tool as witness marks on one side, not top or bottom. If it's the rear mounts, the 'fix' for that is to remove the lag screws on the side mounts (for V-engines) and allow the engine to 'find centre' before drilling new holes and putting the lag screws back in. If it's the transom, you got some big problems!

Chris.....

 

[babikov]

Chris, thanks. I got it. Hope nothing of this concerns my case! Will get the alignment tool and check it. I never had issues inserting the outdrive into the transom, which probably means that it was not too much off. Also, I never noticed any twist of the bearing, which again means that it is close to normal. Regards!

 

[tank1949]

I am replacing the gimbal bearing on my Alpha 1 Gen 2 outdrive of the Mercruiser engine. The old bearing and the seal are out. I wiped off the old grease in the bore and I just looked into it, and I have impression that the engine may not be properly aligned relative to the bore axis. This may be just an impression, since I did not measure anything.

I plan purchasing the tool and checking alignment after the bearing is inserted (new bearing is still out), but my main question is this: Does the alignment process concerns the position of the shaft (or the tool) relative to the bore axis, or it does not matter? Is it somehow measured or adjustred?

I am asking because I learned that the gimbal bearing itself is capable of rotating in its outermost shell quite a bit. Then, it seems possible to have the bearing and the engine perfectly aligned one with respect to another, but both be misaligned relative to the bore axis. Would that be a concern?

If both the engine and the bearing can be twisted, is it a priority to keep the bearing as flat as possible, reaching the desired level of alignment by twisting the engine? And, if the bearing is not in a perfect flat position (I assume it will never be) does it cause a premature failure etc.?

Thanks!

Follow specific instructions for your OD. Some bearings are sealed and some have alignment marks for grease coming from grease fittings. sometime the outer ring get "bumped" when installing complete bearing and is not perfect to the inner. Insert alignment tool and if it doesn't go in, hit tool up and down with heavy rubber hammer to try to center bearing.