Gimbal bearing dimensions

[MagKarl]

I have installed a permalube Sierra gimbal bearing and was under the impression that they were pretty much dimensionally equivalent regardless of brand. This bearing went in easier than the 40 year old original bearing came out. When assessing the alignment I realized that the alignment was near perfect, but the mark on my alignment bar was behind the race of the new bearing. I'm kicking myself for not noticing before the install, the inner race of the Sierra bearing is not as wide as the original and doesn't reach out to my mark. Is this something to worry about?

 

[alldodge]

The bearing should be the same size. I'm not understanding

the Sierra bearing is not as wide as the original and doesn't reach out to my mark.

 

[Fun Times]

What was the Sierra part number you bought?

There are a few changes they did over the years size wise...Here's 2 that may help with some reference points for you to study.

Boatinfo - Bulletins for marine engines and boat related accessories!

Bulletins for marine engines and boat related accessories

boatinfo.no

https://f01.justanswer.com/oldnewenglandmarine/c62477d4-bc89-4896-9e80-b7cb95643540_dustseal.pdf

 

[Bt Doctur]

the inner race of the Sierra bearing is not as wide as the original and doesn't reach out to my mark. Is this something to worry about?
Elaborate please. As long as it was installed fully seated and alignment is good your good to go

 

[MagKarl]

Thanks for the input. I got a Sierra bearing in a parts lot, the box says 18-2100K. There's no way to know for sure since it wasn't a sealed package. Craigslist deal.

The width or depth of the inner race in the direction of the shaft axis is around 1/8" less than the original I pulled out. Tape measure, not calipers. That surprised me.

Looking back at pictures, my new bearing looks like it could be seated deeper, maybe the outer housing is narrow as well. I will probably end up pulling it out to compare the two more closely.

Back story - I pulled the old bearing before I got a new one and alignment bar. Before I installed the new one I temporarily reinstalled the old one without the tolerance ring, slid in the bar, and marked the shaft behind the inner race. Now I have a gap between the inner race of the new bearing and my mark.

It's possible this is not the right bearing.

Or my original bearing was not fully seated when I did the temporary fit up, falsely moving my mark back. I didn't beat it in, assuming without the tolerance ring it would easily seat.

Or maybe the alignment is not great, but it feels smooth and bottoms out solidly.

Or maybe there's something that got into the coupler stopping the bar short.

I'll have to spend some time on it this weekend. I'll pull it out if needed. Any input appreciated.

 

[alldodge]

Was the old bearing installed backwards maybe?
Is there a dot on the bearing, should be yellow?

 

[Rinker95]

Here's a link to the Sierra catalogue page 831 with gimbal bearing application referenced to serial number going back 60 years. http://sierramarine.com/sierra/2019/2019sierracatalog.html#p=831.

Interesting to me that the new inner race is 1/8 (.125) inch (by tape measure) narrower than your original. Starting with the later alpha1 gen2 transoms, the aft side of the inner race was shaved down .090 to accommodate the larger U joints. The 18-2001K is described as matching the OEM 879194A02 (the A02 has the dimension of inner race prior to the .090 shaving). Sounds to me like the bearing and box may be mismatched. (18-2100K also comes with a grease seal.)

As for the bearing going in easier, did you use a new tolerance ring? Or could the outer diameter be a different dimension as in the boatinfo link from FunTimes post #3?

I am a newbie but going through some of the same type issues. I don't know if the width of your new inner race will matter. When buying aftermarket, a good caliper micrometer can be helpful. I've found parts machined wrong (even an alignment bar ! ). Maybe there's a lesson here.

 

[alldodge]

the .090 shave was done for X, XR and XZ Bravo drives

 

[MagKarl]

I don't remember any dots on the bearing. Maybe it was a Chinese knockoff in a Sierra box, hard to say. I'll probably have to pull it and get better measurements because this is not sitting well with me. I'll update you guys when I have something to share.

 

[MagKarl]

I pulled the bearing to get some measurements.

New unknown bearing from a Sierra box within a few thousanths of the original housing outer diameter.

New housing width or depth 1.030" vs 1.088" on old housing, or about 0.058" less than old housing.

Inner race depth of new bearing is 1.180" vs old inner race 1.308", or about 0.128" less. Old bearing has approximately equal inner race protrusion on both sides, new one has less protrusion and not symmetric, less on the outer side if the housing notches face the engine.

This confirms to me why the pen mark on my alignment bar is behind the inner race with the new bearing installed. See comparison pic.

The big question is whether or not this is a problem. Would you run it or buy a Mercruiser bearing for $100?

 

[alldodge]

I have 3 bearings, Merc, Linkbelt I think, and a Sierra. The first 2 are old type greasable, and the Sierra is sealed

Sierra 18-2100
width
inner race 1.248
outer race 1.026
diameter
outer 3.456

Correct me if in error @Bt Doctur but there is no issue if the bearing goes in further, so long as it does go past the inside of the transom assembly. Rhere would be an issue if it doesn't go far enough because of U joints and loads

I don't see a problem

 

[Bt Doctur]

It is recessed slightly, there a pic of the recess in the manual

 

[MagKarl]

I'm mainly concerned with where the drive shaft o-rings sit relative to the inner race.

If I use this bearing I will probably reinstall it with the "long" side of the inner race facing the u-joints as that would most closely match the original bearing.

 

[SeaRay33]

I am actually having the same problem, I have the bearing but the inside is too small for the drive shaft. I can’t get my drive on and it’s making me crazy. The engine alignment tool is too big to fit in the gimbal bearing as well

 

[tank1949]

I don't remember any dots on the bearing. Maybe it was a Chinese knockoff in a Sierra box, hard to say. I'll probably have to pull it and get better measurements because this is not sitting well with me. I'll update you guys when I have something to share.

Pull it and examine it for dot. Then, mic everything for your peace of mind.