Acceptable to shim rear mounts? Mercruiser engine alignment

[Quack Addict]

I am working on a Frankenstein project - it's a 1978 Sea Ray V240 with Mercruiser 260 (Chevy 350) engine. It's getting a new Alpha drive; should be arriving later this week.

I replaced the floor in the boat after I purchased it / knew it needed it before the purchase. While I was had the floor up, I replaced the engine beds (it needed new beds). Problem is, I think my new engine beds are a hair too high based upon the trouble I am having getting the engine aligned. Both front mounts are bottomed out and I can almost get my alignment bar in but eye-balling the centerline of the coupler through the gimbal bearing, it looks like the front of the engine still needs to come down a bit more to elevate the rear.

Is it possible / acceptable to shim the rear mounts (stainless washer) to bring the back of the engine up slightly? Based upon the alignment tool, it seems like about 0.040" (1mm) of shim at the rear of the engine would elevate me enough where I could regain some additional adjusement in the front mounts to get proper alignment coupler / gimbal bearing alignment. The shim would go in under "h" - the fiber washer and "i" - the spring - in the picture below:

Am I in the weeds with the thought of shimming the rear mount, or is this an acceptable solution for my current status? I just dumped a lot of $$$ into a new outdrive, the engine is 100% fresh and I want it all to last a good long time... so I am not looking to save a few cents here only to pay dollars later for a tow bill and later repairs. If shimming is unacceptable, why? Is there some sacred relationship between the transom plate and engine bell housing that rules out insertion of a shim between them???

The only alternate solutions I see are modifying the engine beds (requires engine removal) or removing the engine-side half of the front mounts and shaving the bottom face where it sits against the bottom adjusting nut.

Thoughts?

Thanks!

 

[mkast]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

Remove the engine mounts. While the engine is suspended, and bolted to the inner transom, insert the alignment bar. Adjust as needed, measure. Then you'll know.

 

[bigskiohio]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

did you align your gimble bearing by lightly tapping alignment bar on four sides with bar just started. i think that step gets alot of people as the gimble bearing
moves.

 

[Don S]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

No, you can't. You might be able make that kind of adjustment and get the alignment bar to fit, But don't forget you have ujoints and a drive to fit in there too, and if they are pushed too low due to extra shims under the motor mounts you will have a lot of excess pressure on the ujoints, IF you can get it togehter.
Just get the front mount down to where it should be. As mkast mentioned. Take the front mount off (not the back ones) use a hoist on the front of the engine and adjust up and down to find where it aligns best. Make sure you have the rear mounts installed properly and tightened down to do this.

 

[Bondo]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

Am I in the weeds with the thought of shimming the rear mount, or is this an acceptable solution for my current status?

Ayuh,... I'm alittle Late to this show,... Mkast,+ Don have pointed the Right way,...
When you pull the motor to start over again,... Closely inspect the Rear mounting hardware,...
On such an Old transom assembley,.. The original bushings might be sagging or slipped...
As noted,... The Motor is aligned to the transom,.. Then the front mounts are built up To the motor...

 

[Quack Addict]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

Yep, I think the engine has to come back out. I lifted the front of the engine a hair with a small bottle jack and lowered the lower nuts a bit farther than I could with my 1-1/8" wrench (it's about 5/16" thick). I got to the transom and the alignment bar slid in with some slight resistance. Pulled the bar part way out and adjusted the gimbal bearing and after a couple tries the bar went right in, although the read on the grease didn't show perfect spline contact on the bottom of the alignment dowel, it's not far off. I think the front of the engine still has to go down a hair, but not much.

Anyhow, I spun the crank 180 degrees and I can't get the alignment bar to even start into the coupler. Unless I'm mistaken, this means a junk coupler?

I have a few tricks I can play with my front engine mount setup that I can use to lower them an additional 1/8" or so without grinding glass.

I inspected the aft engine mounts before I installed the engine and they looked fine. The previous owner put a new engine in the boat a couple years back (right before both sides of the block blew out because he didn't winterize it properly) and it looks like they installed new mounts then. Since the engine is coming back out (coupler?), I think I'll replace the mounts for good measure; they are only about $25/ea - consider it preventative maintenance.

 

[Spinnaker]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

U am discovering an alignment issue with my rear mounts also. Here is a little info I found that could be relevant. http://www.perfprotech.com/images/mcmServiceBulletin.PDF Also, I bought a mount kit and the new mounts actually come with two spacers that are cupped much like a bearing race. I plan on inserting these to see if that will solve my issue.

 

[Don S]

Re: Acceptable to shim rear mounts? Mercruiser engine alignment

Please don't reply to old threads. This one is from 2009. I would hope the guy isn't still looking for information after 3 years.