leonid

Engine Alignment - is it time to replace mounts?

12 posts in this topic

When I checked engine (1997 Merc 3.0L) alignment last time this Spring, I've lowered engine front all the way down, but engine alignment tool was tight on splines on its top. I was able to insert it and move it, but not by two fingers, as service manual directs.

Is it time to replace rubber mounts (part#  99297A 1)? Should I replace front mount as well (part# 32833)?
Something else to check?
 

 

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I would also check the hull. Make sure you don't have wood rot where the motor mounts lag in. 

brick

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1 hour ago, Dennis A said:

If splines are hitting on top then engine front is too low.  

Perhaps I've described it wrong - top of the tool was hitting splines. So I needed to lower engine front to raise it on rear. 
https://www.youtube.com/watch?v=86gUZXZYtWY

 

1 hour ago, brick said:

I would also check the hull. Make sure you don't have wood rot where the motor mounts lag in. 

brick

I will check that, thanks. Visually it seems fine. In my 11 years of ownership it was dry. Previous owner was one who shouldn't allowed to have boat though:) 

I've replaced bearing this spring while replacing bellows - old bearing looked ok, no play. Misalignment is not critical, but it should be fixed.

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No, if tool is hitting on top, front of engine is low.  No adjust for rear as it is the pivot point.  

 

Misalignment IS critical unless you want to replace the coupler.

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Old enough for uneven compression of the rubber mounts. Check if the washers are missing. Add any missing ones when changing the rubbers.

You might get lucky with plumped up rubbers. No adjustment needed.  :wub:

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1 hour ago, Dennis A said:

No, if tool is hitting on top, front of engine is low.  No adjust for rear as it is the pivot point.  

 

Misalignment IS critical unless you want to replace the coupler.

It would be correct if opposite.
http://www.ebasicpower.com/faq/alignio.htm

Engine is pivoting around rear mounts, right? It works like seesaw.

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1 hour ago, cyclops2 said:

Old enough for uneven compression of the rubber mounts. Check if the washers are missing. Add any missing ones when changing the rubbers.

You might get lucky with plumped up rubbers. No adjustment needed.  :wub:

So, probably is it better to replace them then.
Engine was removed once I purchased boat when it needed to replace rusted front cover (Previous owner had memory blackout and didn't mention oil is leaking from there). 
Mechanic did the job, and he did good job, but.. it wasn't his boat. I wouldn't be surprised if washers were not reinstalled back.

Should I replace front rubber mount as well?

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Did you align / center the gimbal bearing before you modified the engine mountings? 

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2 hours ago, RoyR said:

Did you align / center the gimbal bearing before you modified the engine mountings? 

Yes, I did.
I did not reinstalled mounts yet.

1 hour ago, wijeff said:

Where do you buy the tools for this type job

Engine alignment
http://www.ebay.com/itm/Alpha-Bravo-OMC-Engine-Alignment-Tool-For-Mercruiser-boat-Marine-USA-made-/272753189761?epid=655240415&hash=item3f815b6381:m:mgf6EcqwbmGO00A-LwDZyYw&vxp=mtr

bellows sleeve tool 91-818162 I made by myself.

For exhaust bellows:
http://www.ebay.com/itm/Mercruiser-Alpha-One-Gen-II-Bravo-Exhaust-Bellows-Expander-Tool-91-45497A1-/112161039534?hash=item1a1d51a4ae:g:wPYAAOSwJcZWeBh7&vxp=mtr

one I made by myself first didn't work well.


for the bearing extraction I've used slide hammer bearing puller from next auto store.

for bearing installation - old bearing aluminium ring and piece of wood.

 

OEM tools are more expensive, don't buy them.

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16 hours ago, leonid said:

It would be correct if opposite.
http://www.ebasicpower.com/faq/alignio.htm

Engine is pivoting around rear mounts, right? It works like seesaw.

Huh?  We went from "alignment tool was tight on splines on its top" to reading grease marks.  

Yes, the engine pivots about the rear engine mounts which are essentially fixed and in about the same vertical plane as the end of the coupler

If you don't set the gimbal bearing correctly you will never show proper alignment with the tool moving freely in and out.  

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