Does the engine still run at all?   

From your description, the damper plate gave up. It's the connection between the engine and the trans and is mounted on the engine flywheel.

Here's a link to a recent thread complete with part numbers and pictures.

The ALTDA-106A plate is pre trimmed, the ALTDA-106 needs to get trimmed to fit.

You can find the plate at ebasicpower.com for around 90 bucks for the pretrimmed version and around 20 less for the non trimmed version. Sometimes the pre trimmed  isn't available lately. You can find them elsewhere too

For your Ford flywheel it needs trimming as shown in the thread and only 3 of the original 6 mounting bolts are used.

It's been used by lots of people around here on CCF.

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=49835&KW=&title=drive-damper-diameter" rel="nofollow -

http://www.correctcraftfan.com/forum/forum_posts.asp?TID=49835&KW=&title=drive-damper-diameter" rel="nofollow - link to thread

Here's a link to the 106 at ebasicpower, the 106A is sold out according to their website

http://bpi.ebasicpower.com/shop/marine-transmissions-and-parts-borg-warner-velvet-drive-zf-hurth-paragon/borg-warner-velvet-drive-parts/drive-damper-flex-plate-for-velvet-drive-26-spline-1004-650-006-as4-k2c" rel="nofollow - link

You'll notice that it says it fits GM engines, after the trim it fits your Ford too 

 Chances are your damper plate looks like mine from Many MANY Moons ago

https://www.correctcraftfan.com/forum/forum_posts.asp?TID=30982&KW=damper+plate&PID=402127&title=damper-plate-failure#402127" rel="nofollow - Damper Plate Failure - CorrectCraftFan.com Forums

KENO wrote: Here's a set of instructions for ya  Remove the motor box and the rear floor piece Disconnect the battery Remove the starter Remove the wires from the Neutral Safety Switch Disconnect the shift and throttle cables Unbolt the coupling and slide the shaft back as far as it will go Unhook the water hoses from the transmission cooler, leave the oil lines hooked up and unbolt the cooler bracket from the bellhousing. The cooler will stay with the transmission. Loosen the pinch bolts on the front motor mounts so the engine can pivot on the mounts. Make sure the bolt is loose and not still tight when the nut is backed off. Leave the rear mounts hooked to the transmission and remove the mounting fasteners from the stringer/cradle. It's a little heavier this way but it's easier to wrestle the transmission around with the mounts on it. Unhook the exhaust hoses wherever it's the easiest for you..Depending on the hoses it might be easier for you to remove them as the engine is being raised Raise the rear of the engine with a bottle jack under an exhaust manifold or use a hoist or whatever other lifting means you have till the engine is about level and block it so it can't fall and ruin your day. Unbolt the transmission from the bellhousing. You probably have 2 bolts and 4 studs holding it on. Slide it backwards till it;s off the studs and set it on a piece of plywood where the rear floor panel was. To me it's easier this way than taking the bellhousing off at the same time Now unbolt and remove the bellhousing, don't forget the little bolts holding the splash shield in place. Unbolt the old damper Bolt the new one on Some people will tell you to tighten the bolts now, some will work thru the starter hole with a crow's foot, u joints etc to tighten them after the transmission is installed and some drill a hole in the bellhousing to tighten the bolts after the transmission is installed. It's your call here on what you want to do. Grease up the female splines Bolt the bellhousing and splash shield back on. Some people bolt the bellhousing to the transmission and install the whole thing at once but it's a whole lot easier to wrestle the 100 or so pounds into place when you can slide the transmission on the 4 studs to get the shaft into the splines. Slide the transmission into place (sounds so easy but you may have to rotate the shaft some to get the splines lined up along with a little lifting. That's why sliding it on the 4 studs is easier. And if you don't have studs, then do what Duane mentioned in the previous post. From here you're just reassembling in reverse order and if you have corrugated exhaust hoses it's easiest to hook them up again as the engine is being lowered. And..........don't forget to check the alignment or somebody named Pete will be all over you  I figure somebody will come along and tell you how they did this or that different but this works pretty smoothly with the least amount of wrestling involved..

reed462 wrote: Damper plate was fixed at the marina on my lake. We put a ALTDA-106 that needed trimming. Mechanic was confident he could fix it and so far so good, no problems until the water pickup belt today.

Not the worst ever but it's pretty bad