I have a 1999 33 ZX and need to replace the hatch actuator and the old one has no part number on it but i think it's made by U Flex. Anyone ever had to replace one.

you sure its not a lenco ?

Do you know the Length, open and closed ? Also the stroke? Check this page - http://www.diamondperformanceparts.com/home.php?cat=301

Pretty sure it's not a Lenco, doesn't look anything like them or any on the Diamond parts website. It is only about 3-4 inchs diameter found in between both motors. The good thing is I can open the hatch manually with another person and it doesn't have any release pin to it seems it was made like that in case it went bad.

Could also be an ACCULIFT - my 2000 22zx had an Acculift which is known to break the splastic gear inside. There may be a name cast into the motor housing. Acculift was doing rebuilds some time ago....when mine took a dump I replaced a LENCO - never had an issue since. If you are not going to install a pull pin setup...use a cigarette lighter and backfeed the system to gain power or install a set of jumper contacts to give the boat power enough to open. The alternative can be very messy and cost way more than you think if the hatch gets locked down with a dead battery.

Found out the actuator is made by Ultra Flex and talked to customer service out of Florida and they did supply donzi with these actuator for a few years, I gave what info I had with measurements and what was on the actuator and they did give me a part number that they said should work. Till about 3 years ago they would rebuild them for you but now you have to find a supplier that carries the actuator. I am trying to track the part down since you don't need the pull pin setup. These actuators are not cheap, but what is on a boat?

Look up 24 inch stroke linear actuator on amazon, theres two brands there with different load and speed ratings, the stronger the slower due to ratio