Questions about coupler/motor mounts/alignment
 

Long story here but really need help...So frustrated I'm ready to light my boat on fire. Anyways, twin 496 HO's. Removed engines at last fall to do maintenance replace the water heater (had to remove the engines to get to it). I did remove couplers/flywheels on both engines in order to mount them on stands. Noticed that the center stringer and lower bulkhead were rotted. Took to a fiberglass shop and had that all fixed/replace. They replaced the center stringer and lower bulkhead. Now, I'm putting the engines back in. Got the port engine in and got it aligned good but in order to do that I have both motor mounts raised almost to the top. It wasn't like that before, but, then again, I'm not sure if the engine was aligned prior. Is that a problem to have the engine that high on the mounts? Now on to the starboard engine. Got that in and can't get it aligned. I was able to get it aligned by having the left motor mount adjusted almost all the way to the top and the right mount about halfway up, then as a double check I rotated the crank 180 degrees and can't even get the tool in. So, now I decided to match up the two motor mounts so that they are basically toward the top of the stud (just like the port engine) and try to go from there. Well, I did that, and you can easily see (by inserting a 1" wood dowel in place of the alignment tool (yes, I have the tool, but I heard that it's good to get it close with a dowel first) that the engine/coupler is offset to far to the right. Does this mean that the coupler is messed up or do I need to try to slide the front of the engine over to the right a little. Could I have put the coupler on wrong? It sure didn't seem like there was anything special that needed to be done when installing the coupler. I appreciate any help/advice.... I'm totally over this project!

Also, yes, I made sure the fiber washers/double wound lockwashers were in place correctly.

sounds like a bravo boat ??, could really use some pictures to help out, what kind of mounts are these.

Sorry, yes, Bravo 1 X drives. Here is a link to the style motor mounts that I have:

http://www.mercruiserparts.com/bam/s...31823/6708/300

Okay those sit on an aluminum angle plate mounted to the stringer correct ??

If you rotate the engine and the fit on the line up tool changes you got something going on with the coupler, flywheel or crank.

33outlawSST: that is correct

Sounds to me like the angle brackets are not back in their original place, do you have anything between the inner transom assembly and the bell housing, are you sure is sitting down on it.

Nothing else in between. yes, it is sitting down on the mounts/brackets good. The brackets are slotted side to side but not sure how much lateral movement I could really get since the flywheel housing is bolted to the inner transom assembly

Does the coupler have the high performance Steel insert that extends out the back?
If so I fought one that was molded crooked
And just like your situation if you rotated the engine the alignment would change.

Yes, that is the style coupler I have. It's original to the boat/engine as far as I know. Did you end up replacing it?

They are for sure back in the original place because I took pretty good measurements prior to make sure

I am 1 1/2 hour drive west of you IF you want to drag it over here this weekend I will help you with it.

They replaced the center stringer and lower bulkhead.

This what you said they did correct, so if you have the engines cranked all the way up, I dont think the L- brackets are in the original position ?? or am I missing something

I would find somebody with a overhead hoist and hook the front of the motor in the middle with the back mounts sitting on the transom plate. A three point pick. Then by adjusting up or down till the line up tool goes in smooth. then work with the motor mounts.

Thanks, I appreciate the offer. I have a forklift lined up for Saturday so I'm gonna give it another shot. Also going to replace the coupler just to be sure.

Correct. Yes, I think you are right about that. But, lets say that the L Brackets are just a little lower than they used to be, as long as I can get the motors aligned without running out of adjustment I should be ok, correct? Or, should the engines not be mounted close to the top of the studs on the mounts? If that is the case I suppose I can put a piece of flat stock aluminum in between the motor mount and L bracket...?

I do have the port engine aligned very well right now, tool slides in and out with two fingers, almost no resistance, and stays the same when rotating the engine in 90 degree increments.

There is nothing difficult about bolting up a coupler, if you use the collared bolts its pretty much self aligning ( centering ) on the flywheel, if this is the coupler you ran last year ( without issues ) then it should be fine, if its rubbing on the bell housing when rotated there's definitely something miss aligned. If you don't have the collared bolts, then I can see it being off centered.

I do have a hoist. I raised the X and engine on my Daytona by installing a 1 inch aluminum block under the mounts. I bought new solid stock type mounts. I tried to buy new aluminum L angle but couldn't find a source for the size I needed. SO I just shimmed the mounts up an inch. The other option IF you have the room is to use a low profile jack and a block above and below to protect the hull and the oil pan. Are you sure that you have ALL of the pieces installed properly on the rear mounts???

ALSO keep in mind that the alignment shaft on a PROPERLY aligned engine should be parallel to the bottom running surface of the boat. You raise or lower the rear mounts to achieve this.

The alignment tool is right when parallel to the bottom of the boat only if crankshaft is parallel to the bottom of the boat ...Point is ,you are aligning to the crank ,not boat

The point I am trying to make is you should be aligning both to the crank AND to the boat.

The alignment tool will ALWAYS be parallel with the crank when the tool slides in properly. BUT if the rear engine mounts sag or are too high or low because of transom angle or a thicker or thinner transom it will cause the alignment tool ( and the crankshaft) to NOT be in line with the boat. Both the tool and the crankshaft should be parallel to the bottom of the running surface. I had this happen years ago and was blowing couplings weekly with an alignment tool that slid right in perfectly. The rear mounts had sagged and this caused me to lower the front mounts to get the tool to align. I shimmed up the rear mounts and then raised the front mounts to get the tool to align. I kept doing this until the tool was parallel with the pad bottom. Never blew a coupling again.

They use a gimbal bearing for a reason so that it can be angled to align with multiple engine positions due to variable boat constructions.

BTW - when I initially couldn't figure out WHY I was blowing couplings I took the boat to the MERC. expert. He said everything was perfect. I blew a coupling that weekend. I had had enough and tore it apart to figure out what was wrong.

If the tool is not close to parallel to the bottom what happens is the output shaft at the front of the U joint will not be in line ( on the same plane ) with the input shaft of the drive. A single U joint cant get out of plane but a dual U joint can. If a dual U joint gets out of plane then it causes side loading of the U joint and that causes side loading of the output shaft inside the engine coupling and IF you have enough HP like I usually do it overheats the coupling and it melts the rubber. A U joint is in plane when it is straight and both input and output shaft are inline, one end is not higher than the other. IF the engine output shaft is higher at the U-joint due to sagged rear engine mounts it causes the U-joint to not only flex because of trimming or steering but it also has to flex to correct the difference between the height of the two shafts.

You guys need to look at a picture of the engine, gimbal, drive alignment before You comment about this. That or go back to school.

IF you don't believe this possible just try it for yourself. Remove 1/4 inch of the shim on the rear mount and then lower the front mount about an inch and You should be able to get the alignment tool to go in with some tweaking. IF the tool goes in then it must be all OK right.

NOT

What shim on the rear mount? There is a fiber washer and a double wound lockwasher. That is ALL! You want to adjust the rear, you gotta fill the transom and cut a new hole. If there are no shoulder bolts for the coupler, and there usually aren't, it is difficult to get the coupler on true. I sit down with a dial indicator and check the run-out on the coupler. You can also use a 4x4 piece of lumber and a come-along to raise-lower the front of engines without dragging it to a hoist or forklift.

Here's the Mercruiser manual boat builders use for pretty much all the rigging installing motors and drives: A lot of cool stuff in it.
http://www.boatfix.com/merc/Install/gas/86017211.pdf

Here's one for the 8.1L if anyone needs it: https://www.scribd.com/doc/9560841/M...allation-guide

To the OP, I have some oe shoulder bolts for coupler mount if you dont have them

Thank you. I actually just picked some up this morning.

Thanks everyone for all the help. I think I will get this figured out!

DEREK - The whole point is that over time the rear mounts CAN sag. ( that is the 1/4 inch - I am not saying they sag this much - more like an 1/8 inch.) 1/8th inch at the rear mount will cause you to lower the front mount about 3/4 inch and make the output shaft angle up badly.

the rear mount can NOT sag. unless the entire transom assy is sagging. the inner and outer are rigid and non-adjustable in relation to each other. i have never seen or heard of the mount surfaces on the inner transom assy bending downward or wearing any measurable depth where the spring washers sit. the same with the mount face on the flywheel cover.

something to check... Make sure you have the correct alignment tool. There are two. The long sleeved coupler takes a different tool than the coupler without the sleeve.

On a second note. Whenever I have re-installed a motor after the stringers have been replaced and it has solid mounts/ aluminum angles on the stringers I have always bought new angles and drilled new holes to get correct alignment.

Derek - IT IS a rubber mount and you are telling me it can't sag. You might want to rethink that comment.

if they do sag ,you replace them

they don't sell shims for them. there is no acceptable procedure to adjust them. if they sag and you shim them, they will just keep sagging.

For the last 25 years ALL of my boats have the rear mounts locked down so they can't move. Just because they don't sell shims doesn't mean that it can't be shimmed.

I didn't tell him to shim it IF it had sagged - I told him to watch out for a sagged rear engine mount.

WHY is it that you guys like to flame people that are just trying to help others?
Just because You have never seen it before yourself doesn't mean that it cant happen.
I deal with weird stuff all of the time.

I have never heard about shimming, but I don't see everything, so I did some research. It appears, that there are some shims and mentions of shims in some various Mercruiser publications.

I did not fully read, nor spend the time to understand which applications and or reasons or etc, but they are out there. The search I did was , in bold,
mercruiser bellhousing optional spacer kit if anyone wants to do further searching.

I did find this interesting, in one of the rear mount set ups if one forgets to install the lockwasher washer that is in with fibre washer: http://www.amarket.com/helpmts.htm

SB - thank you

The proof is right there in writing.

I dont come on here and start...conflicts-usually. But it sounded like you were instructing somebody to do non-standard alterations that were over his head and could-would cause bad things to happen. I have been reading your posts for years. You obviously know what you are talking about. I am not trying to make enemies here.

Neither am I - I guess you just misunderstood my intentions. I just told him to LOOK for sagged rear mounts, This has been a sore subject for me. I got flamed years ago when I brought this subject up and the resident MERC " expert " said that I was wrong and it wasn't possible. I tried to explain how it IS a real problem on older boats. BUT no one would listen. I did have one person PM me agreeing with me. I am just a back yard guy that does ALL of his own work and helps others with oddball problems. About the only thing I hire out is big gellcoat or paint work. I help people when I can even if it costs me time and $.

An update... Put on a new coupler and still have the same problem. I can get the alignment perfect, but then when I rotate the crankshaft 90/180/270 it is way off. I followed the procedure for installing the coupler per the merc service bulletin. I then pulled the engine back out again and checked the runout on the flywheel and it is within spec. Checked runout on crankshaft where the flywheel mounts and the most I got was 0.0015. I also checked the runout on the coupler where the steel hub sticks out and the most I got was 0.005. I'm just so confused about this......

The only thing I can think of is that maybe the flywheel wasn't seated correctly, but I doubt it as I did torque it down to spec which should seat it. I didn't check the runout on the flywheel until I removed it and re-installed it.