898 alignment question.

[WizeOne]

First of all, this is for a friends boat. I am fortunate as I do not have to deal with all these issues with my OMC 800 Stringer.

Forgive me if I use inexact terms. With black anchors there are too many to remember.

Is there any possibility that a wear state of the rear motor mounts could affect alignment? Actually they are not really rear motor mounts. It appears that the ??bell housing sits on the rear mounts and pivots up and down when the motor is out.

The reason that I ask is because the last time I helped with the alignment proceedure, it seemed that our failure to achieve perfection was due to the inability to make any rear height adjustments. This is a stock factory installation with sound front mount stringers and a sound transom.

So in short, could the rear mounts deteriorate to the point that you cannot get a good static alignment. Looking at another post I see that they could wear to the point of not holding under load but we are talking about while things are sitting still.

There is no spline wear on either the coupler or the shaft but this is a fairly low hour '78 boat.

Today we hoisted out the engine (with my forklift) to replace an interim engine installed after a freeze job. Now a proper engine will be reinstalled with proper cam, flat top pistons and a 4 bbl carb. (oooh, I can hardly wait. An 18 ft pocket rocket it will be)

We have a new alignment tool to check things with on the reinstall (previous borrowed one could have taken too many alignment blows) but if something should be done with the rear mounts, now is the time to do it.

 

[Don S]

Re: 898 alignment question.

First of all, this is for a friends boat. I am fortunate as I do not have to deal with all these issues with my OMC 800 Stringer

You are right, all you have to deal with is an Obsolete outdrive and company.
OMC = Obsolete Marine Corp.

So in short, could the rear mounts deteriorate to the point that you cannot get a good static alignment

Absolutely. That is why it's recommended by all modern boat manufactures still in existance, that the drive be removed and alignment checked yearly.
If rear mounts fail, (and they do) the alignment will be off.

Also make sure all the hardware was installed in the proper order below and above the rear mounts. The double lock washer or fiber washer can easily get knocked out of position when the engine is installed. Especially if tried with the drive still on.

 

[bondomerchant]

Re: 898 alignment question.

i know on a early mercruiser the alignment is all in the frt dont know why this would be any differnt went thru hell on a little 120 i used ta have b4 i figured the transom was junk only took me 4 engine couplers ta figure that one outwish some of the shops i went to would chked that for me whole ordeal drove me nuts boats resting in the boneyard now

 

[WizeOne]

Re: 898 alignment question.

.....Also make sure all the hardware was installed in the proper order below and above the rear mounts. The double lock washer or fiber washer can easily get knocked out of position when the engine is installed. Especially if tried with the drive still on.

Does the factory manual show these components? I am a little confused about how anything there can get knocked out of position when removing or installing an engine.(drive removed) It appears (best I can tell sitting in the forklift) that the rear mounts hang off of the assembly that bolts to the transom. Then the ?bell housing sits over those mounts as if they were suspending the bell housing. When you remove the engine, you simply unbolt it from the bell housing leaving the mounts, themselves, untouched. At least that is the way my friend did it for both the removal of the frozen motor, the reinstallation and removal of the interim motor.

Also, how does one tell if the mounts are just plain deteriorated? What are the indicators?

Also, is there any point in trying to measure the concentricity of the coupler, mounted to the flywheel, prior to the reinstallation of the motor. Seems you might be able to insert the alignment tool into the coupler and crank the engine over while checking the rotational alignment (runout) of the tool????

 

[WizeOne]

Re: 898 alignment question.

^bump^

 

[racinrc14]

Re: 898 alignment question.

Wizeone,

You may remember my Ford 302 rebuild thread.

My 302 is coupled to a Pre-Alpha I drive. The rear mounts are incorporated into the rear bellhousing. They do indeed have rubber inserts in them. According to the manual, on the transom plate, there should be sitting a fiber washer, a double lockring washer, then sit the motor with bellhousing attached on top of this 'stack', and, without disturbing the fiber washer and lockwasher, shove the bolt with large washer under the head through the whole mess and attach the nut on the underside. It's a real challenge, especially if the compartment is tight.

I imagine these mounts will wear eventually, but it looked to me like you would have to replace the whole bellhousing to get new mounts.

 

[Bt Doctur]

Re: 898 alignment question.

The rear mount(bell housing) is removed with the motor, you remove the ( 2 )3/4 inch bolts and everything comes out. You remove the dust cover, starter,then the housing. press/burn out the old inserts, clean the hole up and press in new ones till seated.
Guessing ,but I say your too low in the rear mount.

 

[MikDee]

Re: 898 alignment question.

Isn't there supposed to be small springs on the mounts as well?

 

[Bt Doctur]

Re: 898 alignment question.

Using the old style mount you need the double wound spring, If you have the newer type, the spring is not used, but a washer can be used for alignment.
I always try to install the old type because it`s worked very well for all these years.No guess work,but leave it to Mercruiser to try and save 2 cents by eliminating a double wound washer.
If it worked for 100 years, why change?

 

[WizeOne]

Re: 898 alignment question.

Right or wrong, my friend detached the engine from the bell housing then pulled it. The bell housing is still in place so we can't quite see what is between the bellhousing brackets and the ?'transom plate brackets.

I did stop by and pick up a set of mount bushings so he will have them on hand when he pulls the bell housing. They are a simple vulcanized core that is sandwiched between the outer metal cylinder and and the inner bushing like a shock absorber bushing. The mounts came with a seperate brass ring that is chamfered on one side that apparently goes in first, chamfered side up. If there are any fiber washers or springs, they have yet to show themselves.

With these bushings in hand and depending on how they are incorporated, you can see that they could sag, dropping the rear of the motor enough to cause his apparent rear engine vertical alignment issue.