Just How Important is a Torque Wrench Anyway?

[jtexas]

Not owning a torque wrench, I figure those torque values are mostly significant for cylinder heads and crankcases, etc.

A thread on lower units over in the johnnyrude forum has got me wondering. Seems the torque values for attaching the lower unit are all under 40.

Care to speculate on the effect of over-torque? I doubt I undertorqued 'em (but I wouldn't really know).

How paranoid should I be about this?
Next removal should I replace the bolts?
Should I buy a torque wrench and make another pass?

thanks!

 

[swist]

Re: Just How Important is a Torque Wrench Anyway?

Even in less critical areas than the powerhead, the biggest reason for using a torque wrench isn't necessaily to apply a specific number of ft-lbs, but it's to make sure that all the bolts holding an assembly together have the *same* torque. This keeps the load from winding up mostly all on one fastener (for example). And when gaskets are involved it makes sure the gasket is at a uniform thickness around its entire perimeter. A gasket can easily open up if a fastener at the opposite end is overtightened.

 

[JB]

Re: Just How Important is a Torque Wrench Anyway?

A torque wrench is like a feeler guage.

If you can eyeball .020" within +/- .002" you don't need a feeler guage. If not, your magneto is likely to not work well.

If you can torque several fasteners to the same torque so that they will hold and have about the same force applied to them. . . .and that force is appropriate for the diameter, thread count and material of the fasteners. . . well, you don't need a torque wrench. If not you will eventually warp or break something expensive.

 

[Texasmark]

Re: Just How Important is a Torque Wrench Anyway?

When I was young and stupid (now old and stupid d ) I didn't realize how well a fastner would hold with a minimum of torque. I was always breaking bolts off just because I was so stupid. I didn't know about tension from the part, stretching the bolt, or adding a lock washer.

Main advantage I see with a torque wrench is two fold.

1. Understand the range where you are supposed to be tightening.

2. Get all fastners at the same pressure. (You don't need a torque wrench to solve this part; a little concentration will do it.....eyeball if you will).

Mark

 

[rickdb1boat]

Re: Just How Important is a Torque Wrench Anyway?

I don't think I've ever torqued the lower unit bolts. Guess I should, but no problems so far. Now if it was head bolts or the like......

 

[kenmyfam]

Re: Just How Important is a Torque Wrench Anyway?

If it gives a torque setting then there is a reason for it. Not only with outboards but in everday life in a mechanical world. I am a mechanical engineer and will never sign anything off without verifying that all torque settings if specified are correct and the bolt heads marked for position and wired if necessary. There are several reasons for this that I will not go in to but bottom line is as stated above. Use them if specified and sequence tighten if specified as well.

 

[Paul Moir]

Re: Just How Important is a Torque Wrench Anyway?

Reason #1 that TexasMark gave is a good one. You really have to experience how little force 70 inch/lbs is for a 1/4" bolt. And I tend to torque more bolts than most just because it's often just as easy to use the torque wrench as the ratchet. If you look in the front of an OMC service manual, you'll see a list of "Standard torques" for all fasteners depending on their size, along with the special-purpose and more critical bolts.

That said though, there appears to be an awful lot of leeway on your typical lower unit bolt. And many will not even accommodate a torque wrench without an arm extension and the associated math. I may have once torqued one on.

But for other things a torque wrench is handy or essential, and for general outboard service you need two. My inch/lb reading wrench (-240 inch/lbs) gets used 10 times more than my ft/lb reading wrench, which is only used for flywheel nuts and occasionally for connecting rod bolts. Do not attempt to use a ft/lb reading wrench at the low extreme of it's range - accuracy errors of 100% are not uncommon down there.

 

[briannh1234]

Re: Just How Important is a Torque Wrench Anyway?

Another reason to use a torqe wrench is so that you won't over-torque (and potentially snap) something.

- Brian

 

[steelespike]

Re: Just How Important is a Torque Wrench Anyway?

As teenagers we used to mess alot with used B&S motors on go carts.We used the finger method for tightening.1 finger,2 finger,3 finger and so on in sequence and pattern.Of course we also reused most of the gaskets and mixed parts from all the motors and our bst used oil.So we were cutting lots of corners,we had to chip in to buy a gallon of gas at about 29 cents a gallon.
We even took virticle crank motors and mounted them horizontal .Of course those old motors are a lot more forgiving than an outboard.

 

[dingbat]

Re: Just How Important is a Torque Wrench Anyway?

If they specify a torque tolerance I use a wrench. Otherwise I go by feel

 

[gss036]

Re: Just How Important is a Torque Wrench Anyway?

When I was a young aircraft mechanic in the service I spent a lot of time drilling and easy-outing small bolts that my shop supervisor would break off, especially aluminum. Sure made me a beliver in a torque wrench. I have onwed one for the past 40+ years. Then again they are worthless if you "do not" use them ;-}.

 

[Dunaruna]

Re: Just How Important is a Torque Wrench Anyway?

[colour=blue]Over torquing is an interesting term because it implies over tightening. The fact is, in some cases, over torquing can actually UNDER tighten.

 

[ob]

Re: Just How Important is a Torque Wrench Anyway?

Most if not all torque wrenches have an extended handle for leverage within the torque range.Probably one of the most misused tools in the trade.If you don't operate the torque wrench with a smoothe "click "anticipating motion,but rather jerk the wrench till it clicks at its torque setting ,fasteners can be easily and unevenly be over torqued.I see guys at the local tire stores doing it all the time.

 

[bigtwin]

Re: Just How Important is a Torque Wrench Anyway?

As tourque is applied to a bolt the bolt will actually "streach". Too little "streach" the bolt can work loose, too much "streach" and the bolt could snap. There is a sweet spot where the bolt is streached just enough to cause an interferance fit without weakening the bolt or worrying about it loosening. Use a tourque wrench! I owen 3 of them. I payed over $200 apiece (Snap-On isn't cheap but I use them all the time) I am shure that a $50 Craftsman wrench will serve just fine.

 

[Plainsman]

Re: Just How Important is a Torque Wrench Anyway?

For outboard work, what is the max tourqe needed?

 

[Paul Moir]

Re: Just How Important is a Torque Wrench Anyway?

Max torque is usually the flywheel nut, whatever that is. Ranges from about 20ft/lbs to 200 depending on the outboard. Since that's way above most other fasteners, you end up with two torque wrenches. If you shop carefully, you can get the ranges to overlap by just the right amount.

I have a 0-250inch/lb and a 0-150 ft/lb. The 0-150 ft/lb is untrustworthy below about 20 ft/lbs, so that's where I use the inch/lb wrench.

I don't care where you bought your wrenches or how much you paid, if you're not calibrating them or at least checking them then you're kidding yourself. My inch/lb wrench was $100 and my ft/lb one is something like $40. Both were way off brand new. Since I don't use mine professionally, I just calibrate them myself.

It's also important to exercise your wrench if it hasn't been used in a long while. The first click or two will often be "tigher" than torque.

 

[Plainsman]

Re: Just How Important is a Torque Wrench Anyway?

Can you explain calibrating a tourqe wrench?
I was looking at getting one that goes to 60 ft/lbs at NAPA that just has a chart and needle on it.

 

[Paul Moir]

Re: Just How Important is a Torque Wrench Anyway?

I'm not sure how those beam type are calibrated, but usually they don't need to be. They're simple and usually very accurate, just a bit of a pain to use sometimes (like when you can't see the chart). What I wrote above mostly applies to "clickers."

What are you torquing? What's the spec?

 

[Plainsman]

Re: Just How Important is a Torque Wrench Anyway?

I am going to replace the water jacket cover gasket. 150 in /lbs

 

[Paul Moir]

Re: Just How Important is a Torque Wrench Anyway?

Should be just perfect for that. Just make sure you can read 12.5 ft/lbs on the scale with a reasonable amount of precision. +-1 ft/lb should be fine.