Here is my version of a hinge jig that can be used on doors and jambs or frames in any handing combination
On larger doors as the one behind this jig I use 4 hinges in layout but in your situation 3 should be more than adequate.
The layout I use is:7" to the top of the top hinge and 11" to the bottom of the bottom hinge. Yours can vary, and I suggest you use your existing spacings to set your jig up.
The easiest way I have found to construct the jig is as follows: Take the actual door height (80" in your case I would be fairly sure of) and deduct the difference between the bottom of the bottom hinge and the top of the top hinge. In my case it would be 4", so I would make the jig exactly 76" long. I start with a piece of stock about 4" wide and 80" long square it up on the jointer then thickness it to 3/4" or just under. I then rip off a piece about 1 1/4" wide mark the jig with an X to denote reference side and set the 1 1/4" piece aside for now( in the picture the ripped piece is the side on the left side of the jig)> then I crosscut the wider section to exactly the length it needs to be (76" for an 80" door)
Now locate the centers of the the top and bottom hinges (measure 7" + half the height of the hinge to locate the center. If you are using 3 1/2" hinges add 1 3/4" to 7" for 8 3/4"
once these points are located measure between the two marks and divide that measurement by 2 for the location of the middle hinge.
your layout should look like this:
To cut the pockets I use a separate single jig designed to fit the hinge + the thickness of a bushing I use: The bushing is 5/8" OD and 17/32"" ID bushing using a 1/2" diameter bit. This means the pocket must be 1/8" wider than the hinge (3 1/2"+1/8" =3 5/8") and 1 1/8" + 1/16" =1 3/16" deep as shown in the right hand cut drawing.
I make this single purpose jig for two reasons: 1: if I need to tweak the smaller template it is pretty easy to make it slightly bigger or by using bondo as a filler make the pocket smaller. It also allows me to use large radius corner hinges if that is what I have available to me. I try not to use those type hinges as the jig is harder to build but will if I must. Here is a single jig open on the front for easy access
It is constructed using with the large radius corners by drilling two properly sized holes in the corners first then the straight edges are trimmed tangent to the outside edge of the hole. The last cut I do with a straight edge attached to the back and a flush trim router bit. Once the hole is made mark a center line in the back . Now on a scrap set up your router and newly made jig and rout out a mortise pocket for the hinge. if it fits all is well and you can proceed with the larger jig. if not make the adjustments needed to make the hinge fit very well in the pocket. Too loose fix with bondo and recut the edge. too small trim a little off both ends and file the radius to match the fit.
On the larger jig extend the lines on one face so you can locate the jig. I use the open edge of the single jig to locate the start of the cut on the larger jig, flush with the edge you will glue the 1 1/4" piece back to.
Now tack your single jig in place centered on the line you drew with the center of the line on the jig. once again using a flush trim bit (I will take a jigsaw and remove most of the pocket waste) and then trim to the edges of the jig. Locate the jig for the next two pockets and trim those as well. It is very important to locate the centers very accurately using this style jig because the top and bottom are interchangeable depending on the door handing. If one pocket is off even 1/64" the hinge will not fit properly in both the jamb and the door in that pocket.
After all the trimming is done, I lay the ripped off piece back against the cut jig, mark out a relief pockets on the 1 1/4" piece and trim them out with a jigsaw. These particular cuts are not critical to the jig in use, they just give you a place to set a router bit down into to start the cut.
Now you can glue the 1 1/4" piece back on the jig, you do not have to have the elevation between the two perfect just close as you will go back to the planer and reduce the thickness to about 5/8" once the glue is cured.
the only thing left is to locate the jig on the door so it will register easily for depth of cut . I draw a short line at the locations of the hinge pockets (3/16" from the opposite side the hinge will be on and tack the jig down using 1 1/4" finish nails partly driven in. locate the jig from the top to the bottom, reach under the door and make pencil marks about 12" from the end of the jig flush with the door face and using a brad nail with the head cut off as a drill bit, make a hole on the outside of the line you drew on the the jig all the way through and perpendicular to the jig.
Now clip off the pointed ends of two more nails and drive them in the holes you made. That now locates the depth pf the hinge pocket.
IN use the jig is flushed to the top of the door and butted against the two location pins then using the 1 1/4" nails tack the jig to the door. Then set the depth of cut for the router, and cut each pocket fully. using the 1/2" router bit and the 5/8" diameter bushing. if you were accurate with all your layouts you are good to go.
for the jambs to gain the required "nickle clearance" at the top of the jamb I keep a 3/32" shim made of wood to lower the jig the required distance. then I just nail on the jig and cut the pockets the same way.
The real beauty of this jig is in it's versatility : It is short enough to be used in any opening for the door size it is created for; It will accurately locate the hinge pockets when the door is separate of the jamb and will cut the pockets for a left or right hand swing door by just using the opposite end of the jig as the top.
It also excels as in my picture when you need a layout that fits more hinges than just 3 I once built one that used 5 6x6" spring hinges on a 3" thick wine cellar door that would have confounded even me trying to figure out all the pocket locations in the existing frame that was not to be replaced. that was a single purpose jig built with slightly less effort but when the four of us hoisted that door to the hinge pockets the fit was perfect. and our back thanked us at the final setting as it was nearly a 300 # door