Extra large adjustable wrench?

[dutchgray]

I would watch out for large wrenches or slogging wrenches on the second hand markets and buy then as you find them, there can't be a great rush as you are clearly managing to get the job done mangling them off with a pipe wrench currently. Hang the big wrenches on the wall somewhere until you need them.

 

[seber]

I wonder if a Kant twist clamp would work.

 

[rlitman]

Don't most boats that size carry their own propeller wrenches? I agree that using a pipe wrench on the nut will make future proper wrench use difficult.

As pointed out above, pipe wrenches need their teeth dig in in to grip. Making them smooth is not the answer (or you'll round the nut over worse). There are hex style pipe wrenches that grab on three sides, but nothing as big as you want.

I'd start with a bench vise, slice the sides of the jaws off and attach that to a "handle" to make an oversized adjustable wrench.

 

[Maui]

A Cole vise would work. A handle of whatever length you like can be inserted into the end of the vise so you can use it as a gigantic pipe wrench. See attached photo. I have one. They are excellent vises.

 

[2oolhound]

The trouble with a pipe wrench is it is designed for pipe so it only has to reach the center of the pipe (so 3" out for a 6" pipe) to be at the widest spot. A hex nut goes quite a ways past center so pipe type wrench jaws won't reach all the way across the flats like a proper wrench will.

It sounds like you have the budget for something decent. I like post #26 and the others for making a proper wrench to fit. I've taken a nut and cut pieces of steel the length of each flat, held them in place around the nut with magnets then welded them to make a socket but you could also make a wrench that way too.

 

[Kscardsfan]

Have you looked at used large wrenches you can find slugging wrenches often enought pennies on dollar

Industrial surplus is an amazing thing. People will damn near give away that giant stuff since the market for it is so narrow.

 

[Al Borland]

Monkey Wrench.

 

[claymont]

I would guess they would typically have a set of slugging wrenches, or something similar. The problem is a set up to 6.5" is probably more like 10 grand. The pipe wrench has been getting us by, but we are starting to do some bigger boats (just did the one with the 6.5" nut) and I don't like how it tears up the nut. The machinist in me cringes. The nuts generally aren't torqued on super tight, they have a large cotter pin to prevent the nut falling off.

This wrench will do what you want without damaging the nut. I used these wrenches for years. If the area is angled, it might not work.
Memac Chain Strap Wrench

 

[KnurledNut]

 

[RTM]

That is a nice article, but doesn’t talk about that picture. Is that a Delrin wrench?