Mercury 2.0L V6 hard to turn during rebuild

[GWDolphin253G]

I am rebuilding this motor and everything has been going smoothly so far until I have been thrown for a loop when I tried to close up the crankcase. All new pistons and rings are well lubricated and sliding smoothly on new bearings that have been put together on correctly aligned rods that are torqued with new bolts. Crankshaft is freshly polished and has all new main bearings and seals too.

At this point the end caps are on but not screwed on to the top half I am about to install and torque down. Everything still turns beautifully. I install the crankcase cover and torque the large bolts...all good. Same with the smaller bolts...still all good. I go to torque the end caps and the turn gets really tight. I loosen the end caps, and it turns smooth again.

I have looked for a problem and have inspected everything but I cannot figure out what I am doing wrong. I measured and micro-measured clearances and everything checks out. I installed the lower main bearing with the lettering facing down and up with no change. Both top and bottom o-rings sit true and are not caught or causing undue pressure.

Someone please tell me that I am a dumbass and have overlooked something minor.

Thanks!

 

[CharlieB]

Re: Mercury 2.0L V6 hard to turn during rebuild

If I understand correctly, you are saying that the crank turns freely until you torque the lower bearing carrier on?

Check the inner races radius to that of the matching position on the crank. ink one surface, reinstall, then remove and look for any contact marks indicating a lack of clearance causing the bearing not to seat completely, thus pinching the rollers as the carrier is tightened.

 

[GWDolphin253G]

Re: Mercury 2.0L V6 hard to turn during rebuild

The lower end cap is not a bearing carrier but just a cap with the seals. The lower bearing is held onto the crank with a retaining clip and it sits snug to the crankcase as the two halves come together. The cap touches the lower bearing as it's put on and torqued. The o-ring then seals the outer radius of the cap.

The crankcase also has a shape that stops the lower bearing between it and the clip (that has a groove for it).

The upper main bearing installs how you describe and I will do your test just to see.

Any other help will be appreciated. I did a 2.0L before and this did not happen. I am clearly overlooking something.

 

[CharlieB]

Re: Mercury 2.0L V6 hard to turn during rebuild

If the radius on the ID of the inner race is smaller than the radius/fillet on the crank and collide, then when the seal carrier contacts the outer race it can 'push' the outer race in a couple of thou, 'pinching' the rollers side-to-side between the races, causing your dragging.

Is the replacement bearing of the same manufacturer as the old bearing? Or the same # but another brand, the radius may NOT be identical.

 

[GWDolphin253G]

Re: Mercury 2.0L V6 hard to turn during rebuild

It's the same part from a different manufacturer. I will try it again with the original to see what happens.

It's not my first rebuild and I am guessing the same thing but it's strange to see that happen. It would be a first for me.

 

[CharlieB]

Re: Mercury 2.0L V6 hard to turn during rebuild

If radius collision is the problem, I'd be tempted to take a small stone wheel in a die grinder and enlarge the clearance angle on the inner race ID until the bearing seats correctly on its side.

Careful not to overheat and be certain all grinding residue is removed and perfectly cleaned.

 

[GWDolphin253G]

Re: Mercury 2.0L V6 hard to turn during rebuild

I don't know if I want to do that to a new part. I've used these parts before on other Mercury 2L and on Yamahas mwithout this issue. I really, really am hoping there is something else I need to look at.

Like I said, hopefully I am overlooking something else.

Thanks!

 

[GWDolphin253G]

Re: Mercury 2.0L V6 hard to turn during rebuild

Changed to the old one and nothing changes. I am about to loosen the rod bolts and remove the crank and start over again. Hopefully someone knows something.

Thanks!