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Engine Alignment

R

ronkrifchin

Member
To All,

I have a 2002 176 with a 3.0l MCM that had a bad coupler and I had to pull the motor. Installed a new coupler and reinstall the motor everything went well as far as I could tell.

Engine reinstalled and everything looks good (Gave myself an Att-a-boy for a great job....toooooo soon) but the alignment is off. So I began the alignment procedure...

Now the problem and I'm really stumped????

Just a note: Before I pulled the motor the alignment was actually good even considering the bad coupler...

Using an alignment tool I can't insert it very far? Upon a visual inspection, that is looking through the gimbal bearing into the coupling, I can see it's out of alignment. Looks like to motor is too high and needs to be lowered. OK, so I thought it's not a big deal... So I began lowering the jack screw on the mount and here's where the problem appeared... I had to lower the engine all the way that is, the jack screw all the way down and there's no more adjustment ... and the engine is still too high.... Although the alignment tool goes in all the way it's not easy and needs to be forced... not good...

I know the rear mounts are critical to the alignment so when I reinstall I was very careful with to install the fiber and steel washers as original.

As far as I can tell I haven't changed anything that would have caused such a dramatic misalignment? But here I am, it's still too high and no more adjustment???

It's clear the rear is too low. Is it possible I install the bellhousing incorrectly? Can it be rotated 180 degrees? Honestly can't think of any other way this misalignment could happen...

Any input on this would be greatly appreciated.

Thanks to all..

Ron
 
..................

Now the problem and I'm really stumped????

Just a note: Before I pulled the motor the alignment was actually good even considering the bad coupler...

Using an alignment tool I can't insert it very far? Upon a visual inspection, that is looking through the gimbal bearing into the coupling, I can see it's out of alignment. Looks like to motor is too high and needs to be lowered. OK, so I thought it's not a big deal... So I began lowering the jack screw on the mount and here's where the problem appeared... I had to lower the engine all the way that is, the jack screw all the way down and there's no more adjustment ... and the engine is still too high.... Although the alignment tool goes in all the way it's not easy and needs to be forced... not good...

I know the rear mounts are critical to the alignment so when I reinstall I was very careful with to install the fiber and steel washers as original.
As far as I can tell I haven't changed anything that would have caused such a dramatic misalignment? But here I am, it's still too high and no more adjustment???
Look closely at where you installed the springs (if equipped).

It's clear the rear is too low. Is it possible I install the bellhousing incorrectly? Can it be rotated 180 degrees?
The flywheel cover (what you're calling a bellhousing) cannot be rotated........ the bolt pattern is specific to the rear engine flange.

Honestly can't think of any other way this misalignment could happen...
Click to expand...



Here's an example of the geometry and the goal!


Drive Coupler alignment explained 5.jpg

Drive Coupler alignment explained 4.jpg
 
If the alignment goes away and destroys a coupler something caused the alignment to go bad. Usually its the rear mounts that collapse and cause the motor to drop down.If you just replaced the coupler and nothing else then you missed what caused the damage in the first place
 
Bt Doctur said:
If the alignment goes away and destroys a coupler something caused the alignment to go bad. Usually its the rear mounts that collapse and cause the motor to drop down.If you just replaced the coupler and nothing else then you missed what caused the damage in the first place
Click to expand...


Bt, Yes that is exactly what I've done. I replaced the coupling but have not identified or corrected the root problem.

Just for clarification, your reference to the rear mounts, you are referencing the two mount port and starboard in the stern of the boat, correct?

If it is indeed the two rear mount, can you tell me if there is a measurement or some other way to tell if they actually failed? Do they normally fail together?

If I need to replace them, must I remove the engine again or can they be replace while in the boat?

Thanks again for the help.

Regards,
Ron
 
Check to see if you can turn the fibre washer or check if the upper and lower housings are basically touching.Post some pics if you can.
 
Rick,

Thanks for the pictures that are a great help. Still trying to figure out exactly what the problem is and how to solve it. Yes the engine is out of alignment but what actually caused it and how do I fix that?

Thanks,
Ron
 
Screenshot_2016-05-11-09-02-21_zpsq9lkax2l.png
 
There's no adjustment to the rear mounts. You should double check that all is in the correct order and seated into the recessed area of the transom plate mounting bosses.
The main adjustment is at the front of the engine. There shouldn't be much side to side discrepancy, it's mainly up and down to align the axis of the crankshaft with the drive.
Are you sure that you're reading it right? If the coupler looks high that means the front is too low. Bringing up the front will lower the back end. Does that make sense?
Also, when using the alignment tool, you should be putting a skim of grease on it as a way to tell where the high spot is. I'm sure you know that just double checking.
 
Another long-shot possibility if you have this style drive coupler!

shopping


The drive coupler's mounting face must fit tightly against the crankshaft flange via the flywheel's surface.
If the coupler did not pull up against this area absolutely parallel and tight, the inner coupler splines will not be correctly aligned with the center of the crankshaft, as o2batsea mentioned.

If this occurred, you will never achieve drive coupler alignment.

If you question this, turn the engine over 180* and take another alignment tool reading.
If the "incorrect" reading changed locations, you may have found your problem.

Or..... you you have a drive coupler that is misaligned right out of the box (doubtful).

Again...... a long-shot!



If you have this style drive coupler, that idea pretty much goes out the window.

shopping


.
 
o2batsea said:
There's no adjustment to the rear mounts. You should double check that all is in the correct order and seated into the recessed area of the transom plate mounting bosses.
The main adjustment is at the front of the engine. There shouldn't be much side to side discrepancy, it's mainly up and down to align the axis of the crankshaft with the drive.
Are you sure that you're reading it right? If the coupler looks high that means the front is too low. Bringing up the front will lower the back end. Does that make sense?
Also, when using the alignment tool, you should be putting a skim of grease on it as a way to tell where the high spot is. I'm sure you know that just double checking.
Click to expand...


o2batsea,

I took great care when I reinstalled the rear mounts, but that doesn't mean I did it correctly. My plan is to go back and double check them before I do anything else. As to the side to side play, there's very little if any once the mounts are tightened. And yes, the adjustment is totally with the front mount and the jack screw. As I said earlier, I've adjusted the screw to it's max and there is absolutely no more adjustment left! Clearly, the front of the engine is still too high to achieve the proper alignment.

ALso, Bt gave me some things to check on the mounts and I'll be doing that in the next day or so...

I'll post a picture soon...

Thanks,
Ron
 
Rick,

Thanks for sharing your thought on the coupler...

I have the triangular design and as you point out, it's almost impossible to screw up the installation and alignment. With the motor out in my garage, the old one came off without a hitch, I cleaned up the flywheel with a wire brush and some oil and the new one when on in no time. Should have known it was too easy and something else was going to pop up!!! At this point, I'm not ruling anything out... LOL

Thanks for including the diagrams of the mounts. It's always handy to have these at the read just for comparison.

Thanks again,
Ron
 
Rick,

A quick note about the rear mounts.

Just for clarification, I have the Original Design Mounts in the boat now.

Do you know if the new design mount will raise the rear of the motor any higher than the original design?

Thanks again,
Ron
 
ronkrifchin said:
Rick, A quick note about the rear mounts.

Just for clarification, I have the Original Design Mounts in the boat now.

Do you know if the new design mount will raise the rear of the engine any higher than the original design?
Click to expand...

I do not!
Take a look through this info, and see what you can learn.
mercruiser Alpha drive rear engine mounts old style vs new style - Google Search


Or, perhaps Bt Doctur can answer that question.


My thoughts are...... if you did not replace the actual mounts (in the inner transom plate bosses), the rear engine elevation should not have changed.



Also, keep in mind that the Gimbal Bearing's inner race itself articulates in an orbital fashion.
When the drive was removed, the inner race may have been repositioned.
If so, when you insert the alignment tool, you might be sensing the inner race having been repositioned, in which case you would adjust it with the tool.

That said, if you can fully insert the alignment tool through the Gimbal bearing and into the drive coupler, this would not be an issue.



.
 
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There will be no difference in height at the rear regardless of whether you use old or new, but since you reinstalled what was there, we assume that no dimensions are different from before the parts were replaced. Again if the hole is high at the rear you want to RAISE the front of the engine.
 
I have installed the new type replacing the old style and it does not change the height ,if any. I believe the new type is longer to compensate for it because the doublewound is not used and a SS washer is supplied if necessary to make a minute correction.
Did you install new rear mounts? If yes, were they installed correctly?

My thoughts are...... if you did not replace the actual mounts (in the inner transom plate bosses), the rear engine elevation should not have changed.

it will change the height ONLY if they have collapsed
 
Last edited:
Also, keep in mind that the Gimbal Bearing's inner race itself articulates in an orbital fashion.
When the drive was removed, the inner race may have been repositioned.
If so, when you insert the alignment tool, you might be sensing the inner race having been repositioned, in which case you would adjust it with the tool.
Click to expand...

Not on a Mercruiser.
 
Bt,

No I didn't change anything other then the coupling? I'm obviously missing something here and I don't know what?

The original coupling failed and I'm guessing at this point it was as a result of a poor alignment.

All I can be sure of is the front jackscrew adjustment is all the way down on the motor mount and there is still a slight misalignment? See pictures attached

BTW, I check the fiber washer on the rear mounts and I am not able to turn or move it. Also, the rear inner transom mounts and the rear engine mounts appear to be incontact with one another with the fiber washer being in between the two... Was not able to get pictures but will tray again later...

Again,

Thanks to all for your help on this..

Ron
 

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Because you can’t get the alignment in spec. There’s only a couple of things that can go wrong

rear mounts collapsed evidence is the lack of alignment if front is all the way down like you are the rear mounts have sagged down .
New coupler is bad rotate engine and recheck
stringers are bad and collapsed but the alignment issue you see would be opposite, ie you would be running out of adjustment on the high side
 
Last edited:
Dieter said:
Because you can’t get the alignment in spec. There’s only a couple of things that can go wrong

rear mounts collapsed evidence is the lack of alignment if front is all the way down like you are the rear mounts have sagged down .
New coupler is bad rotate engine and recheck
stringers are bad and collapsed but the alignment issue you see would be opposite, ie you would be running out of adjustment on the high side
Click to expand...

Dieter,

Thanks for the input. I'll be check them out to see if I can come up with the problem.

Will keep you all posted.

Thanks very much for the help,
Ron
 
remove the rear bolts and check the height of the top of the rear mount in relation to the top of the flywheel cover. I`ll take some pics of the housings I have for comparison, you can also measure between the RED lies
click to enlarge
 
Last edited:
Bt Doctur said:
remove the rear bolts and check the height of the top of the rear mount in relation to the top of the flywheel cover. I`ll take some pics of the housings I have for comparison, you can also measure between the RED lies
click to enlarge
Click to expand...

Bt,

I'll give it a try but it's going to be next week before I can get to it.

Will let you know what I find out.

Thanks,
Ron
 
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