OMC Rod Cap Alignment Tool

[Mas]

Just curious...does this tool prevent misalignment due to "slop" in the bolt holes...or due to distortion as the bolts are torqued and is equalized by lateral pressure of the tool...and later locked when the rods are torqued?

Wouldn't the rod bolts have shoulders to automatically align rod & cap?

Sorry, I was bored and was just reading my manual...with no intention of removing my connecting rods.

The tool seems like "overkill!" Couldn't alignment just be "eyeballed?"...or by running a straightedge along the side & looking for light?

MAS

 

[SKEETR]

Re: OMC Rod Cap Alignment Tool

The rods are actually milled as one piece and split after being frozen in nitrogen or some similar fasion. The only alignment shoulders are crystalized metal at the break. Agreably I scratch my head on this method myself but I am not a mechanical engineer by any means. The tool actually will compress the cap to fit as it becomes slightly expanded after the break. When installed correctly you can barely see the break if at all.

 

[Mas]

Re: OMC Rod Cap Alignment Tool

The only alignment shoulders are crystalized metal at the break.

What do you mean by this? I'm a little confused.

Thanks, the weather is changing & boating is probably over until spring...I'm a fair weather boater...thus the boredom!

MAS

 

[Dhadley]

Re: OMC Rod Cap Alignment Tool

The rods are refered to as a cracked rod. As mentioned the rods are made as one piece then there are 2 holes drilled in each side and the cap is actually broken or cracked off. There's a lot more to it but that's the short version. The theory is that nothing fits back together like a crack. That's why you cannot interchange the caps.

In my opinion the tool is worthless. The cap can be lined up quicker and sometimes better by hand. I've seen rods that would not line up with the tool but will by hand.

 

[F_R]

Re: OMC Rod Cap Alignment Tool

The rod and cap are made as one piece, then then the cap is broken off. The break line will be ragged and will fit back together exactly, the bumps on one matching the low spots on the other. Substitute "bumps" and "low spots" for "crystallized metal" and you will understand.

 

[jbjennings]

Re: OMC Rod Cap Alignment Tool

Very Interesting Reading for me!!!!
Thanks from me, too!
JBJ​

 

[R.Johnson]

Re: OMC Rod Cap Alignment Tool

To me: that tool is cumbersome to use, and could cause the very problem you want to avoid.

 

[woody66912]

Re: OMC Rod Cap Alignment Tool

i have coworker that uses the tool and he has wrecked more rod caps that way .i have done it both ways it took longer with the tool.i still like the finger nail or sharp pencil method.

 

[Mas]

Re: OMC Rod Cap Alignment Tool

Well,

I managed to learn something...a lot more than expected. Thank you!

I've rebuilt a couple of car engines that seemed to run just fine without using a similar tool...never even heard of it until reading the OMC manual. Clearly, I'm not an expert in either field!

Is this tool common only to OMC, the marine industry, or other?

MAS

 

[Mas]

Re: OMC Rod Cap Alignment Tool

Also, since the tool was referenced in my manual '94 20hp 'rude, I would expect to have the "cracked rods...right?"

Makes me want to tear down my motor just to see it!

MAS

 

[R.Johnson]

Re: OMC Rod Cap Alignment Tool

Mas: Your engine has the cracked rods.

 

[F_R]

Re: OMC Rod Cap Alignment Tool

The "cracked rods" date way back many, many moons, over 50 years of moons.

 

[Dhadley]

Re: OMC Rod Cap Alignment Tool

There are other motors that used cracked rods but most auto motors use cut rods. A cut rod can be redone but a cracked rod cannot. A cut rod isn't normally hard enough to run needle bearings.

 

[iwombat]

Re: OMC Rod Cap Alignment Tool

Dhadley - is it the hardness or the gap between the rod and cap? Some hi-perf harley rods are actually billet aluminum. But, since harley rods aren't split at all (you assemble the crank around them) they run needle bearings just fine.

 

[Dhadley]

Re: OMC Rod Cap Alignment Tool

That's a whole different kind of rod, a solid or 1 piece rod. Some Yamahas and other outboards are like that too. Motorcycles, PWCs etc.

The bearing surface has to be extremely hard or the needles will wear out the surface quickly. A typical auto rod uses a babbit bearing which doesn't move (we hope not) so the surface hardness is much less of a concern.

 

[iwombat]

Re: OMC Rod Cap Alignment Tool

Well come to think of it, those Al rods are typically for racing engines which get torn down and rebuilt either yearly or after exploding in impressive fashions all together. Regular OEM and aftermarket rods are generally hardened steel.

 

[Mas]

Re: OMC Rod Cap Alignment Tool

So, I'm guessing that this technology would not transfer to the "mains" since the block would be cast separately and difficult to "crack"...right?

MAS

 

[Mas]

Re: OMC Rod Cap Alignment Tool

Oops,

Sorry, I forgot we're talking about two-strokes with crankcase halves!

MAS

 

[Dhadley]

Re: OMC Rod Cap Alignment Tool

Most 2 stroke outboards have split sleeve roller bearings for the mains. That's why the front half is kept with the block half as a set.

 

[Mas]

Re: OMC Rod Cap Alignment Tool

Interesting. With all this new info, I'm wondering what I pushed out of my brain to make room? I'm getting old! Hopefully not the wife's birthday?

MAS