Coupler - Not Centered

[TimeZone]

Need some advice on my engine coupler. Can't find any specification in the service manual and reading through the engine alignment thread, there is no real limit on "centered and true".

So...Doing an engine alignment and got the spline/grease marks looking perfect on the alignment tool. The tool would engage the splines with no effort. But when I turned the engine 90 deg. it would not go in at all. Seemed like the coupler had moved to the side. I noticed there is a dimple in the back of the coupler which you can see in the picture. I'm assuming the dimple is from the manufaturing process and is dead center. While cranking the engine, I could clearly see the dimple moving arround indicating quite a bit of run-out. Probably between .030" and .060".

What's normal for these things?

2005, 4.3, Alpha I, Gen II

 

[TimeZone]

Re: Coupler - Not Centered

No one knows?

 

[fmalott]

Re: Coupler - Not Centered

if you got the tool to go in right why are you turning the engine? align the tool then put your outdrive on. what was the reason you pulled the outdrive in the first place. when i recently replace my gimble bearing i put the tool in then i tightened down the motor . when you pull the tool out are you moving the bearing

 

[undercover]

Re: Coupler - Not Centered

I've never seen a standard for run out in the coupler. A little run out is probably ok because the tolerance between the driveshaft and coupler is greater than the alignment tool and coupler. If the tool slides in easily with each 90 deg turn of the motor, you should be ok.

 

[wellcraft-classic210]

Re: Coupler - Not Centered

Some runout is apparently fairly common on older couplers and you verified yours has runout by turning your engine.

I am not an expert on this but here is what I found on mine;

You can see how much runout you actualy have by using a 1 in. od shaft about a foot long inserted into the coupler and rotating the crank shaft while watching.

I aligned mine by finding the happy medium with the 1 inch shaft (I had less than 1/4 inch runout as i recall ) and followed up with the alignment tool finding it was a little tight in some positions and slid in easily in others. Its been running fine for several years. I will replace it if I ever have to pull the engine but I am avoiding that for now.

If your coupler has excessive rounout then it may be due for replacement. If your engine was out of alignment prior to your work it may have caused the runout. Rubber will get distorted over time when left under pressure ( its referred to as set ). Needless to say the coupler could be damaged in some other ways also.

Good luck !

 

[TimeZone]

Re: Coupler - Not Centered

if you got the tool to go in right why are you turning the engine? align the tool then put your outdrive on. what was the reason you pulled the outdrive in the first place. when i recently replace my gimble bearing i put the tool in then i tightened down the motor . when you pull the tool out are you moving the bearing

Yup - What you mention is how the Merc manual says to do it. But if you search the many threads on this topic in this forum, the recomended procedure it to check alignment at every 90 degrees to confirm that the coupler is centered and true. I'm glad I did, because it looks like my coupler is whacked and explains why I have some vibration.

 

[TimeZone]

Re: Coupler - Not Centered

I've never seen a standard for run out in the coupler. A little run out is probably ok because the tolerance between the driveshaft and coupler is greater than the alignment tool and coupler. If the tool slides in easily with each 90 deg turn of the motor, you should be ok.

Good point about the alignment bar being a tighter fit to begin with. The problem is that at 90 deg from good alignment, I'd need to hammer the alignment bar to get it in.

 

[Don S]

Re: Coupler - Not Centered

Is this a new couple or an old coupler? If original coupler and the engine set for a long time with the drive full up, it could be pushed down slightly and taken a set.
Turn it back to where the alignment is good, then turn the engine 180? and see if it goes in. If not adjust the engine the direction needed and count how many turns of the adjusting nuts it takes to align it again.

if you got the tool to go in right why are you turning the engine?

Because that is how you check to see if the couple is bad or not.

 

[TimeZone]

Re: Coupler - Not Centered

... If your engine was out of alignment prior to your work it may have caused the runout. Rubber will get distorted over time when left under pressure ( its referred to as set ). Needless to say the coupler could be damaged in some other ways also.
Good luck !

Interesting you mentioned that. The engine was in fact quite a bit out of alignment. Almost 1/4" to high and the grease seal behind the gimbal bearing showed visible wear at the top. Also have a bad yoke seal on the upper unit which might be related as well.

 

[TimeZone]

Re: Coupler - Not Centered

Is this a new couple or an old coupler? If original coupler and the engine set for a long time with the drive full up, it could be pushed down slightly and taken a set.
Turn it back to where the alignment is good, then turn the engine 180? and see if it goes in. If not adjust the engine the direction needed and count how many turns of the adjusting nuts it takes to align it again.

Thanks Don,

I believe it's the original coupler. I didn't expect that these things could develop a set. I can tell you that the engine was way out of alignment. (almost 1/4" to high).

Checking the range of adjustment at 180 deg makes a lot of sense. I actually did that, but was not counting the turns as a form of measurement or comparison. I believe it was about 2+ turns of the nut to get it nice. I assume thats too much run out.

-Ron

 

[Don S]

Re: Coupler - Not Centered

Is this the first time you have checked the alignment? How long have you owned it?

 

[TimeZone]

Re: Coupler - Not Centered

Is this the first time you have checked the alignment? How long have you owned it?

I just bought the boat end of March and I'm working out the kinks before I set sail.
I think the previous owners only did fluid changes. :facepalm: So this is probably the first time an alignment has been done since it left the factory.

 

[mr300z87]

Re: Coupler - Not Centered

I just went through the same process on my new to me boat. When I took my drive off the alignment was so off I could not get the bar to go in at all. To make matters worse got it all aligned went to tighten the adjuster nuts and my starboard side mount stripped. Installed new mount aligned and was out for first splash last weekend. Keep at it your hard work will pay off.

 

[TimeZone]

Re: Coupler - Not Centered

Thanks everyone for all the insight.

I've ordered a new OEM coupler and I'm pulling the engine Friday night.

Decided it's not worth taking the chance on the old coupler since I already did the gimbal bearing and grease seal as well as getting a new yoke and re-seal on the upper unit. If all goes well, the engine will be back in on Saturday.

It will also give me a chance to have a closer look at the timing cover and check for cracks/leaks. Hopefully I don't have the same fate as achris.

Cheers - Ron

 

[TimeZone]

Re: Coupler - Not Centered

Engine is back in the boat!
Problem resolved...

Looks like I had a spun coupling.



When I bolted the new coupling onto the flywheel, we cranked the motor with the plugs removed. I was quite surprised to see how much wobble there was. The hole in the back of the coupling was centered and not moving arround like the old one was, so we took a chance and put the engine back in. Alignment went much better. I could push the bar in with one finger at 0 and 180 degrees. 90 and 270 were with some resistance. I also turned the engine by hand with the alignment bar in place and observed no more than 1/32" of movement on the bar.

For curiosity seekers, I took an iPhone video of the new coupling. I suspect each coupler is going to be quite different and getting one that is perfect is just luck of the draw.