Mercruiser alignment issues

[Rick Stephens]

Not replaced gimbal bearing. Gimbal is smooth and no rust but not new. +- 4 and 1/2 thousands run out at end of flywheel. So, flywheel appears to have gone on w/o crap between crank and wheel. No noticeable wobble. I'll center coupler tomorrow with tapered 3/8 bolts and also measure runout with MC spline tool inserted. Coupler splines look good.

That's a great plan. Simple and easy to reproduce before reinstall. Best of luck!

 

[tank1949]

Plan didn't work. I am still having issues after rotating motor 180 degrees. I installed a new transom and within specs!!! New inner transom plate and rear engine mount holes are not "wollared" out. Gimbal bearing is in great shape. I tried the hammering with 4x4. That did work. My tool is not out of round. My coupler's threats have squared ends and are not rounded due to wear. So are my spline shafts. I am my wits end on this one. I mic'ed the flywheel to be +-4 thousands difference near flywheel gear. I tried the centering technique per MC bulletin. That didn't work. I missed something but I can't see it?

 

[Rick Stephens]

If I read you right, you checked run out on the coupler with a dial indicator and came in 4 thousandths? Did you stick your alignment tool in the coupler and mount the dial indicator to the block and then turn the motor over? Just wanting to see how you got your numbers.

Doing the motor rotation test won't be effected by transom or motor mounts much at all. Turning the motor over 1/2 turn just isn't going to move things around much unless it is really horribly bad, which yours ain't. I wouldn't expect motor mounts, transom or gimbal bearing to have any real bearing on this particular testing issue. Has to be in the coupler or flywheel I would think.

 

[Mad Props]

If I read you right, you checked run out on the coupler with a dial indicator and came in 4 thousandths? Did you stick your alignment tool in the coupler and mount the dial indicator to the block and then turn the motor over? Just wanting to see how you got your numbers.

Doing the motor rotation test won't be effected by transom or motor mounts much at all. Turning the motor over 1/2 turn just isn't going to move things around much unless it is really horribly bad, which yours ain't. I wouldn't expect motor mounts, transom or gimbal bearing to have any real bearing on this particular testing issue. Has to be in the coupler or flywheel I would think.

I agree... the only thing theoretically changing when rotating the engine is the flywheel or coupler... my money is on a bent coupler (probably from running with a rotten transom and stringers).

 

[tank1949]

If I read you right, you checked run out on the coupler with a dial indicator and came in 4 thousandths? Did you stick your alignment tool in the coupler and mount the dial indicator to the block and then turn the motor over? Just wanting to see how you got your numbers.

Doing the motor rotation test won't be effected by transom or motor mounts much at all. Turning the motor over 1/2 turn just isn't going to move things around much unless it is really horribly bad, which yours ain't. I wouldn't expect motor mounts, transom or gimbal bearing to have any real bearing on this particular testing issue. Has to be in the coupler or flywheel I would think.

Thanks for replying!!! You too MAD! I agree with what you are saying, but I don't do this for a living and was trying to list what I had performed to resolve issues or identify any mistake that I had made. Hopefully, someone would pinpoint the culprit.

I couldn't run dial on spline tool while inserted into coupler. My magnetic arm/base wasn't long enough. Believe me, we tried!

I inserted tool into coupler with motor out, but there seemed to be too much "droop" on spline tool indicating wear (maybe < 1/4" at very end of 2 foot), but that slop or droop may have been engineered into coupler to assist in reducing vibration. I guess being about 2 feet long and weighing 7-10 lbs the tool also forced drooping. I suspect Mad props concern about rotten transom has to be the reason, or a factory imperfection. However, I believe that there would be more wear and not warping. Ironically, gear and coupler teeth look in great shape. TEETH ARE NOT ROUNDED!!! We have motor back in and linkage/hoses/grounds installed. I guess that I will have to play with adjustments to get an average and lock down everything. I am sick of f-nnn with this boat. I am fortunate to have shop/tools and boom and lots of friends who pitch in to help pull motors if need be later on. I'd be curious to know how much out of round is acceptable for coupler and techniques to measure it.

However, I did find what appeared to be traces of 5200 or adhesive on OD gear splines (both ODs). Former owner may have accidently gotten the 5200 on it (wasn't much) or put it on there to dampen vibration? I don't think so. Or, perhaps mechanics wrapped duct tape on spines to protect them while performing other work and some of the adhesive remained. Back in the 60s we poured all kinds of crap into older manual transmissions to quieten them. Again, thanks for replying.

 

[alldodge]

replace rotten transom.
could freely insert and remove alignment tool
spun motor over 180 degrees and tried inserting alignment tool. It was difficult.

If the transom plate is at an angle and not parallel within 1/8 (2mm) to outer surfaces, this will keep it from aligning within spec.


When installing motor, was the rear bolts installed snug, motor lifted up off front mounts just bearly hanging from the thermostat housing. Then lower front motor mount nuts turned by hand so that they just touch the bottom of the mounts.

Once there motor is lowered on mounts and from then on each nut is adjusted up/down the same amount of turns?

 

[tank1949]

Exactly what I did. THX! I do not want to do this again. I had less then 1/16" on inner and outer. I have pretty much figured couple is not PERFECT!

 

[Mad Props]

AllDodge I agree with your point on the transom being critical, but I think tank said he was able to get it aligned okay, but then it was bad once the motor rotated... If the transom was out of alignement/spec, I don't think he would have been able to get it aligned at all. Again, why I'm assuming its a coupler issue...

 

[alldodge]

Yes I agree, it looks like coupler issue, but if this was the case, then there should be a place where the alignment would be found again, but right now its not being found. This is why I also mentioned the start from scratch alignment setup. Lifting from thermostat housing should set it to level on rear mounts

 

[Rick Stephens]

Yes I agree, it looks like coupler issue, but if this was the case, then there should be a place where the alignment would be found again, but right now its not being found. This is why I also mentioned the start from scratch alignment setup. Lifting from thermostat housing should set it to level on rear mounts

Note: If the transom or stringers were ever rotten and the motor sat down in use or in storage, the coupler is trash and nothing anyone does will fix that except replacement with a square one.

Another note: If you own a dial indicator, then creativity is all that is between using it and finding things impossible to make work. I can think of a dozen ways to mount a dial indicator to read a coupler. Easiest probably being a stack of washers and a bolt through a metal bar on one of the bellhousing holes on the block. Then attach your mag mount to that bar. I probably would disassemble a u-joint and use the splined yoke shaft to check how much runout on the coupler.

Last note: AD is of course right. If in doubt, start from the beginning. But I think you can assume the coupler is not centered and the motor is coming back out.

Rick

 

[tank1949]

Yes I agree, it looks like coupler issue, but if this was the case, then there should be a place where the alignment would be found again, but right now its not being found. This is why I also mentioned the start from scratch alignment setup. Lifting from thermostat housing should set it to level on rear mounts

I built harness and used turnbuckle in its center to pull on chain perpendicular to front mounts. I did find sweet spot(even grease witness marks on tool), but after rotating motor 180 degrees, sweet spot became sour. I suspect that coupler's alignment in not 100% true internally. I have to average. THX!

 

[achris]

The only things that can cause the alignment to show variations on the alignment bar when the engine is turned 90/180/270 degrees are engine related. Bent crankshaft, flywheel out of flat, coupler damaged or dirt under the mounts of f/wheel or coupler. Things like that.

Any amount of misalignment of the transom will only result in a constant, but NOT VARYING misalignment of the coupler to gimbal bearing.

Chris......

 

[tank1949]

The only things that can cause the alignment to show variations on the alignment bar when the engine is turned 90/180/270 degrees are engine related. Bent crankshaft, flywheel out of flat, coupler damaged or dirt under the mounts of f/wheel or coupler. Things like that.

Any amount of misalignment of the transom will only result in a constant, but NOT VARYING misalignment of the coupler to gimbal bearing.

Chris......

Thx!!! Couple has to be less then perfect, but gear teeth look perfect. I suspect its issue was created a factory. If rotten transom that I earlier replaced caused any issues, and they would have, I strongly believe coupler's gear teeth would have worn prematurely. I cannot EASILY see gear teeth wear or my OD's gear teeth wear. Thx to all!

 

[Rick Stephens]

Thx!!! Couple has to be less then perfect, but gear teeth look perfect. I suspect its issue was created a factory. If rotten transom that I earlier replaced caused any issues, and they would have, I strongly believe coupler's gear teeth would have worn prematurely. I cannot EASILY see gear teeth wear or my OD's gear teeth wear. Thx to all!

What causes a coupler to be non-centered is a rotten transom or stringers that allow the motor to hang from the coupler. Either direction does the same thing, if the stringers under front motor mounts are soft and the front of the motor drops, the weight of the motor puts a bind in the coupler. If the rear of the motor is unsupported by either collapsed mounts or a soft transom, again, the motor hangs in the back.

Since a coupler is a splined sleeve vulcanized into a rubber flywheel mount, the weight of the motor will, over time, pull the sleeve off center. It can and will do this without affecting the teeth in the spline. Running the boat with an out of center coupler ends up flexing and then overheating the rubber and failing the coupler there, not at the teeth.

If your coupler is not concentric it needs to be replaced. If you aim for a 'sweet spot' all you'll accomplish is walking back one day when the coupler rubber fails.

 

[tank1949]

what causes a coupler to be non-centered is a rotten transom or stringers that allow the motor to hang from the coupler. Either direction does the same thing, if the stringers under front motor mounts are soft and the front of the motor drops, the weight of the motor puts a bind in the coupler. If the rear of the motor is unsupported by either collapsed mounts or a soft transom, again, the motor hangs in the back.

Since a coupler is a splined sleeve vulcanized into a rubber flywheel mount, the weight of the motor will, over time, pull the sleeve off center. It can and will do this without affecting the teeth in the spline. Running the boat with an out of center coupler ends up flexing and then overheating the rubber and failing the coupler there, not at the teeth.

If your coupler is not concentric it needs to be replaced. If you aim for a 'sweet spot' all you'll accomplish is walking back one day when the coupler rubber fails.

thx!

 

[tank1949]

What causes a coupler to be non-centered is a rotten transom or stringers that allow the motor to hang from the coupler. Either direction does the same thing, if the stringers under front motor mounts are soft and the front of the motor drops, the weight of the motor puts a bind in the coupler. If the rear of the motor is unsupported by either collapsed mounts or a soft transom, again, the motor hangs in the back.

Since a coupler is a splined sleeve vulcanized into a rubber flywheel mount, the weight of the motor will, over time, pull the sleeve off center. It can and will do this without affecting the teeth in the spline. Running the boat with an out of center coupler ends up flexing and then overheating the rubber and failing the coupler there, not at the teeth.

If your coupler is not concentric it needs to be replaced. If you aim for a 'sweet spot' all you'll accomplish is walking back one day when the coupler rubber fails.

Rick,

The former owner of my current boat is much older than me and in not the best of health. It is hard to get reliable information from him. The best I can tell is that boat's Alphas /V6s were replaced with Bravo 1s about 1995(gimbal housing serial numbers are for 1995). I assume V8s too. Strokers about 4 years ago, according to build sheets and no-rust condition (salt water boat). Owner or mechanic reused Alpha Triangle shaped coupler. Although not as strong, in my opinion, they will work. Be advised that I do not have to force coupler on and off when 180 degrees out, but it is definitely a tighter fit. I suspect that I will order new Alpha coupler, just to be safe-thx! Bravos are way too expensive!

 

[alldodge]

If the coupler goes out its not going to take the drive out, you'll just smell smoke and stop moving.

With what your saying about difficulty inserting after turning, I might just run it, that is unless your going offshore. Inland lakes not so much. Could give it a few hours running and recheck and inspect

 

[tank1949]

If the coupler goes out its not going to take the drive out, you'll just smell smoke and stop moving.

With what your saying about difficulty inserting after turning, I might just run it, that is unless your going offshore. Inland lakes not so much. Could give it a few hours running and recheck and inspect

Thanks for replying AllDodge. Rick also had good advice and logic. I do plan on offshore. I've ordered a new coupler, just to be safe. Boat came with Alpha couplers, so I order latest design Alpha coupler which also comes with grease fitting (useless in my opinion). I'd have to take out a loan for new Bravo coupler. I am just too old for twisting wrenches in the Florida sun. I want this boat idiot proof and all good to excellent condition if I plane on chasing Blue Marlin at 71 years of age. THANKS AGAIN!

 

[Mikey N.C.]

What type of front motor mounts ? What are those mounts setting on ? Are u hand barring motor over or starter , with plugs out ? With this much trouble , finding problem. Heck bolt dial indicator to floor of boat. Turn over motor with starter and see if motor might be pulling front mounting bolts up and hanging. Just a thought.

 

[Mikey N.C.]

Can I ask , the seasoned I/O guys here , on standard rotation motor , engine does torque over to port. And pulls on Mount on starboard?