Torque Wrench Size??

[Steve_C]

I am upgrading my toolkit for life aboard in the very near future and getting rid of most of my old tools. I have two VERY old torque wrenches from 40 years ago. I want to upgrade to a nice new one but there are so many choices out there. I am heavily leaning towards a 3/8 drive digital version, but even those come in a HUGE range of sizes.

What is the maximum torque that I need? I will be on a newer Lagoon 42 or 450S. I would prefer to not go too large to keep the size and weight down. I rarely use a torque wrench, but it is a must have in my opinion.

Thanks!

[billknny]

Originally Posted by Steve_C

I am upgrading my toolkit for life aboard in the very near future and getting rid of most of my old tools. I have two VERY old torque wrenches from 40 years ago. I want to upgrade to a nice new one but there are so many choices out there. I am heavily leaning towards a 3/8 drive digital version, but even those come in a HUGE range of sizes.

What is the maximum torque that I need? I will be on a newer Lagoon 42 or 450S. I would prefer to not go too large to keep the size and weight down. I rarely use a torque wrench, but it is a must have in my opinion.

Thanks!

Just running down a mental checklist of bolt sizes, I am guessing the biggest on your future boat will be the engine mounting bolts. Assuming those are 3/4" grade 5 bolts, that would be ~200 foot-lbs. 300 ft-lbs if Grade 8.

Crankshaft end nuts might be bigger, but hopefully you're not messing with them!

[tkeithlu]

Getting 200-300 foot pounds out of a torque wrench shorter than two feet (100-150 pounds on the handle) will be difficult, even if you stand on it. On the other hand, you'll be in a yard if you have to change your engine mounts, or adjustment thereof. For most work, a 3/8" torque wrench covers both the socket sizes and the torques you need. It need not be fancy; a click wrench is fine.

[Steve_C]

Originally Posted by billknny

Just running down a mental checklist of bolt sizes, I am guessing the biggest on your future boat will be the engine mounting bolts. Assuming those are 3/4" grade 5 bolts, that would be ~200 foot-lbs. 300 ft-lbs if Grade 8.

Crankshaft end nuts might be bigger, but hopefully you're not messing with them!

I am not too worried about anything that large, as I will not necessarily need to use a torque wrench to deal with it. I will have a really large 1/2 break-over bar to loosen and tighten things. I am more concerned about things that I can break by over-tightening. I have been working on engines my entire life and have a pretty good feel for most things, but there are some that really need consistent torquing in my opinion.

Thanks for the input!

[slug]

Originally Posted by Steve_C

I am upgrading my toolkit for life aboard in the very near future and getting rid of most of my old tools. I have two VERY old torque wrenches from 40 years ago. I want to upgrade to a nice new one but there are so many choices out there. I am heavily leaning towards a 3/8 drive digital version, but even those come in a HUGE range of sizes.

What is the maximum torque that I need? I will be on a newer Lagoon 42 or 450S. I would prefer to not go too large to keep the size and weight down. I rarely use a torque wrench, but it is a must have in my opinion.

Thanks!

day to day work is 6 to 12 mm

Not many large diameter fasteners on a small boat

My torque wrench is 1/4 inch

[a64pilot]

You really need three to cover all, but whatever you get stay away from the digital ones.
Remember every time you use it to set the torque back to zero or min range of the wrench.
Stay away from digital as it’s too many things to break and gives you nothing really. An old type deflecting beam is actually probably the best as they never go out of calibration and are pretty much indestructible, but do require a little finesse in their use.

[roverhi]

Engine head bolts and keel bolts are two things that come to mind that would require a torque wrench. Both would need at least a 1/2" drive wrench that goes to a 100# or more. Would stick with a simple moving beam/no ratchet wrench. My fancy dial in the torque and click ratchet wrench locked up when I didn't use it for a couple of years in the damp environment of Hawaii. Probably wouldn't have lasted months in the salty humid environment of a boat.

[tkeithlu]

Let's hear it for simplicity, following roverhi's lead. I used a deflecting beam wrench for twenty years, but moved to a click wrench for precision and to cover tasks inwhich I could not clearly see the face of the wrench.

If you've been torquing bolts for a long time, you're not likely to shear one just because you are not using a torque wrench. You have a feel for how tight a bolt or nut should be. That leaves situations where you have multiple fasteners that need to be the same torque for flatness's sake, and individual critical fasteners.

A 1/4" click seems a bit small to me on a boat; it's closer to what I would expect on my small Honda trail bike. The span of sockets only goes up to 1/2 inch. 1/2 inch goes down to 7/16"/11mm, just catching the 1/4x20 bolts (7/16"). 3/8 has the span of sockets without adaptation, and as Goldilocks said, is "just right."