I think I eff'ed up

So...total rookie mistake. During my rebuild, i was installing the connecting rods to the crank shaft. Since i didn't have a torque wrench, i went to lowe and bought me a nice kobalt. Straight out of the box, i set it for 32 ft. pound. I torqued it and it clicked. Done right? NOPE! When i was done with all 4 rods, i inspected all 4 again to make sure everything is cool. This is where I eff'ed up. I didn't check for calibration. I assumed it was good. Turns out i over torqued one of the screw. It cracked my rod and the end piece. FAK!

Considering the stress the rods go through during regular operations or at high RPM, the rods must be strong. I know this rod is no longer reuseable...but I just want to hear someone else tell me that . I already ordered another. So this is done right?





Now I wait another week for another rod to arrive. I'm so darn mad right now. Stupid mistake hindering my progress. FAK FAK FAK!

No you cannot use the rod.

Maybe it should be INCH lbs, ft lbs seems high !

NOPE------- 32 FT-LBS is the correct torque.

I think he is damn lucky the rod broke when he could SEE it, instead of on the river at 5k RPM.

32 ft lbs does seem pretty high but that's what the book has it at. It was also my first time installing rods, so i wasn't torquing in stages. Also a good lesson because i didn't have the alignment tool, wasn't even thinking that each side had to be flushed. I just made sure it was lined up the best it could but didn't do the pencil or finger nail test. So overall, it's the best thing that could have happened actually.

When I have to torque something that low on the ft/lbs scale I convert to in/lbs easier to split into 3rds

????--------These are bolts made from high tensile strength material.--------Alloy steel at around 180,000 psi tensile strength.----------------Torque on these bolts has been specified at 32 FT-LBS or about 370 INCH-LBS since about 1960 on thousands and thousands of these motors !!!

I wonder why it cracked the rods at only 32 ft lbs. Maybe from not doing it in stages.

If you did not have the cap on correctly as they are broke at factory it will cause this. Usually they will strip before they split. If cap is incorrect say from different rod you need to replace the others too. Overtightening should have not split it but a high spot from different cap would act like a chisel and split it....JMO

faztbullet said:

If you did not have the cap on correctly as they are broke at factory it will cause this. Usually they will strip before they split. If cap is incorrect say from different rod you need to replace the others too. Overtightening should have not split it but a high spot from different cap would act like a chisel and split it....JMO

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I did something that's for sure. I had all the rods and caps bagged appropriately so i don't think that was it. Possibly it wasn't lined up correctly and i torqued one side to 32 lb then the other side 32 and that may have done it. Who knows...lets hope i don't repeat myself with these replacements that are coming in.

You torque it in steps... Install rod cap and hand tighten(snug) and check alignment. Torque the bolts to 10ftlbs and recheck,then 20,then 32.Use a small drop of oil on threads..no loctite

I loosened all the caps of the other 3 rods and rechecked. (still waiting on the new rod to arrive). While playing around with hand tighten the bolts, i was not very successful with getting the cap to be flushed with the rods. I don't have the alignment fixture tool (P/N 3967490) from OMC but I did see a picture of what it looked like. I came up with this to get the cap flushed with the rods. Obviously this worked for me, may not work for others but I thought i'd through it out there. I'll create a separate thread as a reference for someone who is struggling with the same thing i'm going through.

Dad was a machinist and he had this aluminum rectangular stick laying around. I cut it into two small pieces. I glued one of it to the top of the clamp, then i slipped the other piece on the bottom and slowly tighten and readjusting the aluminum piece to make sure it's straight. I tighten it by hand. took it off to check and it was flushed! Took pictures with the cracked rod to show what i did. Didn't think about taking photos when i was working on it earlier.

Maybe it is an illusion but the bearing surface on that rod looks suspect to me.

Good idea there.......If its done right you wont need alignment tool, I have built hundreds without it...

racerone said:

Maybe it is an illusion but the bearing surface on that rod looks suspect to me.

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It's just dirty. that's the bad rod, so there's some debris on it. It's smooth as a baby's butt if i wiped it down.

Yes that rod is toast. Just be thankful you found it before A closing up the crankcase and B running it! You absolutely dodged a much bigger bullet by noticing it before fully assembling and running the engine. I would definitely follow what others have already mentioned, torque in increments, do not torque one side down all the way with the other "Free." I usually do 3 increments to bring the bolts up to spec. I've never seen a rod break in that location and while only tightening the rod cap screws.

Also, this is the type of work where it pays to have a high quality torque wrench and you absolutely get what you pay for! Harbor Freight or your local hardware store specials are great if you need to "Customize" tools to fit some whacky space but for stuff such as this where precision matters, spend the money up front, it'll be worth it in the long run. Coming from someone who learned the hard way when I started to build outboards at age 13!

Good luck with it and hopefully you'll be making wake soon!