Last time I spoke to him he has paid them just never put the tag on the boat, could I go the abandon route since its been at my In-laws house for about 5 years?

Well if I could avoid having to buy a boat Vs. titling it ... I'd like to go that route. I have a buddy in AZ that might be able to steer me in the right direction ... but wanted to see if anyone else has come across this issue.

If your POSITIVE that it has --OR-- actually on the title, as in your
(Moms name here) -->OR<-- (dad's name here)
you can get an affidavit of release of interest, and your mom can sign that in front of a Notary of Republic, or at the DMV and have it put in your name, as that designates that your mom --OR- your dad can sign off on the title without the others knowledge.
If it has any one of these 3 designations:...
> -AND-,   
> Right of Survivorship, 
> or it is not specified as OR between their names

then they will "legally" both have to sign off on it.

I have the PTI Rey for the trailer and both my parents are on it and it states "OR" on it. The last time I send the Rey for the boat it still had both parents on it and had it as "OR" also. Trailer is Rey here in CA which I can have switch to my name now but don't want to do the leg work on that until I'm sure I can get the title. Mother has no problem doing it just need to request it, just not sure what form I need from AZ to do it by mail or maybe I should try to call and see if they can help me that way?   

I've been through it, it sucks, and it causes more turmoil than needs to be. Like you I don't talk to my dad, and he was just being that way with something he didn't even want just for spite !?!?