350 crusaders possibly clutch plates welded together

i have a 81 silverton 31 c just got it this yr , drove it over from a local marina to mine was great . First time we went out for a short spin, hit a big wake from a bigger boat , rocked it good . port motor woulnt start found out it was a rotor on distrib. cap . easty fix . coming in to my slip was a bitch with only starboard motor , and it was stuck in forward . every time i went to put it in reverse it stalled . cables seem fine had a few guys look at the possibilites. they think clutck plates welded together . how easy is that to do

You likely have Velvet Drive transmissions coupled to Walter V drives. You should start by checking the level of transmission fluid (Dexron) in the transmission as it is hydraulically controlled. If they aren't shifting it's usually low fluid level. Also check level of lube oil in the V drive if so equipped as long as you're in there.
Velvet drives are quite common and parts are readily available. Worst case scenario is you have to pull the transmission out and rebuild it. Can be done by relatively competent home mechanic. A overhaul kit is about $200-ish for the parts.
link to service manual here:
https://www.marinepart***press.com/BW_Schematics/BW71C_72C Direct Drive_Reduc_Ratio.pdf

If the fwd clutch plates are warped (more likely than welded) the shaft will usually rotate in fwd when the gear is in neutral...if that's the case, not only should the clutch parts get replaced but the whole gear should be checked for wear/damage. It may be faster to just get a rebuilt unit this time of year.

is the lube oil different from trans oil i checked the tranny level in the starboard motor was good , and is it in a different location

If you have V drives, I seem to recall they get 90 gear oil.

the velvet drives take dexron III ATF...and the v-drives, depends upon the brand you have...Walters can use SAE 30 motor oil or APG80 gear oil...Crusader V-drives take 80w-90 gear oil...

It would help all of us help you if you identified what is actually in your drive train...