Crank Question

[Sydmoe]

Hey there fellas!<br /><br />I rebuilt my 1988 OMC 350 last year and somehow the bolt that holds the dampener on the end of the crank got stipped. Probably from turning it over manually so many times during assembly. Anyways, Since the water is a little too hard right now here in Canada to go boating I pulled the motor to try to fix it properly. In my excitement to get it in the water last year I just used the stongest loctite I could find and got it as tight as possible befoer it started to slip. Needless to say I can't turn it over manually any more for fear of it just spinning and doing more damage to the thereads.<br /><br />Has anyone tried to Helacoil the dapmner bolt before and do you think this is an acceptable method of repair? Will I be able to torque the bolt with out fear of tearing out the helacoil?<br /><br />Thanks

 

[Buttanic]

Re: Crank Question

A helicoil would work fine. Unless the snout of the crank or the dampner bore is worn the press fit will hold it on. In the future do not use the bolt to turn the engine.

 

[KaGee]

Re: Crank Question

Originally posted by Buttanic:<br /> In the future do not use the bolt to turn the engine.

Absolutely! A strap wrench on the pulley or harmonic balancer works great without damage to either. <br /><br />Sears sells a real nice one for $20 including a strorage case.

 

[f_inscreenname]

Re: Crank Question

I don't know. I think if I had the motor out I would try to re-tap the threads and use a slightly larger bolt. You will only have one chance to fix it. After the motor is in, as you know, there is no access.

 

[Sydmoe]

Re: Crank Question

Originally posted by KaGee:<br />

Originally posted by Buttanic:<br /> In the future do not use the bolt to turn the engine.

Absolutely! A strap wrench on the pulley or harmonic balancer works great without damage to either. <br /><br />Sears sells a real nice one for $20 including a strorage case.

Sounds like a good idea when the engine is out of the boat. But once in the boat the bilage area is pretty cramped to get anything around the balancer and with the belts on you wouldn't have much luck using the strap on the pulley. Appreciate the suggestion though. <br /><br />I was thinking along the lines of f_inscreenname because I thought it would handle me torquing the bolt more than the helacoil. However, I have read about alot of people using Helacoil to fix stipped head bolts which also require a fair bit of torque. If they work well in that application than I would imagine they must be able to handle my problem as well.

 

[Bondo]

Re: Crank Question

A Heli-coil which is built out of SSteel, Will take Much More Torque than Any threads cut in Cast Iron(which is what Your crank is made of)...................<br /><br />Be Aware, The Crankshaft bolt is Fine Threads........<br />Fine threaded Heli-coils Are Available, but Much Harder to Find.........<br /><br />Going to a Larger Hole,+ Bolt is Not the best approach............

 

[KaGee]

Re: Crank Question

Originally posted by Sydmoe:<br /> Sounds like a good idea when the engine is out of the boat. But once in the boat the bilage area is pretty cramped to get anything around the balancer and with the belts on you wouldn't have much luck using the strap on the pulley. Appreciate the suggestion though. <br />

Well, yea, you have to remove the belts! Takes me all of 2 minutes to do both belts?? <br /><br />Lets see.. 2minutes of time vs. stripping main crank bolt threads or worse yet... snapping the bolt head off... hmmmm, which do I choose??<br /><br />Good luck.... was only trying to help.

 

[Sydmoe]

Re: Crank Question

Originally posted by KaGee:<br />

Originally posted by Sydmoe:<br /> Sounds like a good idea when the engine is out of the boat. But once in the boat the bilage area is pretty cramped to get anything around the balancer and with the belts on you wouldn't have much luck using the strap on the pulley. Appreciate the suggestion though. <br />

Well, yea, you have to remove the belts! Takes me all of 2 minutes to do both belts?? <br /><br />Lets see.. 2minutes of time vs. stripping main crank bolt threads or worse yet... snapping the bolt head off... hmmmm, which do I choose??<br /><br />Good luck.... was only trying to help.

Sorry KaGee, Didn't mean to sound like a **** to your suggetion. It is a good one I am sure I will use in the right circumstance.

 

[Peter J Fraser]

Re: Crank Question

Cummins Diesel and I think Caterpillar have (or had) a thread insert called 'KEENSERT' that was available in both NC and NF threads upto about 1,1/16". They used a std tap for the OD and the insert was locked by driving SS dowels down the side to prevent it turning back out.<br />Those inserts will hold upto 350 + ft lbs torque. <br />Might be worth looking into.<br />The biggest problem tho is getting it all square if you are re-drilling and tapping a new thread.<br /><br />Good luck.<br /><br />Peter

 

[Bondo]

Re: Crank Question

The biggest problem tho is getting it all square if you are re-drilling and tapping a new thread.

I have to Agree..............<br />Anything short of having a MachineShop do it,<br />It'll be tough to Keep It Square.......

 

[rayjay]

Re: Crank Question

ARP makes a stud kit to retain the damper. You probably have some good threads left in the crank, they are just deeper than the bolt will reach. Install the stud in the crank snout with some locktite. Put some tension { but not full torque } on the nut while the loctite sets up overnight.

 

[jimmythekid]

Re: Crank Question

it probably stripped from, somebody using the bolt to force the dampener on. Helicoil threads are MUCH stronger than what was there originally. I agreee with Buttanic on this one, IF the crank snout and balancer are good, once the balancer is on all the way, it will probably stay on, even with loose threads and loctite.