Mercruiser 5.7 rear motor mounts

[aj10203]

I recently got finished replacing the gimbal bearing, water hose, u-joint, exhaust, and shift cable bellows, the trim sender and limit switches, and lower shift cable on my 1989 Larson San Marino DC 250 with Mercruiser 260 and alpha one. I had a hard time getting it into alignment and after messing with it for hours, figured I had it "good enough" (not 2 fingers to insert/spin/remove, more like 3/4 fingers). The outdrive went on pretty easy, so I figured it was close enough to aligned. Well on the first journey out this year I believe my drive coupler gave out (probably on its way out anyway). I smelled burning rubber and had some smoke but no fire, temp gauge was right at 140 degrees. So now time to pull engine and inspect/replace coupler, and I will also be replacing the rear engine mounts at the same time. I already purchased a new coupler (Sierra 18-2321 Engine Coupler Replaces 12632A6), and 2 engine mounting bolt kit (Sierra 18-2141 Engine Mount Bolt Kit Replaces 10-97934A1). I am wondering if I also need to purchase the bushing that gets pressed into the rear motor mounts? (EX. http://www.michiganmotorz.com/motor-mount-p-9206.html) or does the kits I purchased include everything I need? I am hoping to complete this project this weekend.

Thanks in advance.

Also, what else should I inspect/replace while I have the motor out as preventative maintenance? I have already read to check Y pipe for rot..

 

[alldodge]

In most cases if the bar won't go in easy, then one side of the motor is higher/lower then the other. This is why its best to raise the front of the motor, adjust the lower motor mount nuts to bottom of mounts, then lower motor. Now adjust the nuts up or down evenly until alignment is achieved.

Either that way or need to get another tool to place on the alignment bar which can tell you which way the nuts need to move.

In any case, look close at the mounts and see if they are at the same spacing from bottom of bushing to bottom of flywheel housing. Need a depth gauge or something else real accurate

 

[aj10203]

In most cases if the bar won't go in easy, then one side of the motor is higher/lower then the other. This is why its best to raise the front of the motor, adjust the lower motor mount nuts to bottom of mounts, then lower motor. Now adjust the nuts up or down evenly until alignment is achieved.

Either that way or need to get another tool to place on the alignment bar which can tell you which way the nuts need to move.

In any case, look close at the mounts and see if they are at the same spacing from bottom of bushing to bottom of flywheel housing. Need a depth gauge or something else real accurate

Thanks for the advice. When I first tried to align the engine I did not have the ability to lift the engine. Now that the coupler went (I believe) I am just going to bite the bullet, pull the engine and replace everything that could have caused/contributed to the problem. When I get the new rear motor mounts in I do plan on using the front lifting eye to align this time. Still curious as to if I have to buy the motor mount bushings. Or is the fiber washer/double wound lock washer the component(s) that fail, and the rubber/metal bushing can be re used?

 

[alldodge]

My opinion; others differ

I don't see motor mounts wearing out under normal recreational use. If it was commercial use, sure.

You need the rear mounts to be even and preset. If ONE is higher or lower then the other this is the issue/problem. If you need to use only a fiber washer or bother fiber and spring is determined by which mounts are installed.

Your motor is a Merc 260, so your going to use spring washers

 

[Maclin]

Look at the exhaust flappers in the Y-pipe while the engine is out. Might just replace them anyway, real easy with the engine out.

How did you get back to the launch once you had the smell and some smoke, just idle all the way? If the coupler went while you were at speed I am surprised you got back without a tow is all.

 

[Bt Doctur]

those look like there smooth so you will need the double wound springs
Before you pull the motor look at the rear mounts. If there not the same height they have failed

 

[aj10203]

Look at the exhaust flappers in the Y-pipe while the engine is out. Might just replace them anyway, real easy with the engine out.

How did you get back to the launch once you had the smell and some smoke, just idle all the way? If the coupler went while you were at speed I am surprised you got back without a tow is all.

I was actually taking my boat from the launch to my marina for the season, and I noticed the smoke and smell just as I was pulling in. Im just glad this happened this early in the season and i should be able to get it fixed quickly.

 

[aj10203]

those look like there smooth so you will need the double wound springs
Before you pull the motor look at the rear mounts. If there not the same height they have failed

when you say they have failed what exactly do you mean? the double wound spring failed? or the rubber pressed in bushing failed? starting to think I should just replace those rubber bushings just to be on the safe side.. Ill look into the exhaust flappers as well..

 

[Bt Doctur]

the core separetes from the rubber and the mount drops down

 

[achris]

My opinion; others differ

I don't see motor mounts wearing out under normal recreational use. If it was commercial use, sure.
...

My original engine (inline 6) did have sagged rear engine mounts, but I suspect that was because the inlines have the full weight of the engine on those mounts. The V engines carry most of the engine weight on the side mounts. That said, if you're pulling the engine for a failed coupler, it would be unwise not to replace the rear mounts given the age of the engine.