1987 Donzi Z29 Red
 

I am looking at purchasing one. What is the best way to improve the engines. It currently runs in the 60's (mph) but I would like to get better performance out of her. What do reupholstering jobs run as well as well as rearranging the seating area? Thank you for your time.

Cockpit interior 2-5k depending on what you do and what needs done. Engines depends on what you have, the number of hours, what you wnat and how deep your pockets are. You could easily spend 5k or more per engine for a 5-10mph gain.

A friend of mine had one new back in the mid-eighties and took me for one of the best boat rides I've ever had. The boat was a 65mph or so boat if I remember but he had it trimmed up and leaping over some pretty big rollers coming out of Boston Harbor. Remember looking back and seeing the wake stop then start again then stop etc as we left the water. I know it doesn't answer your questions but great boat.
Matt

Have a good survey done. Those vintage boats were known for rotten stringers and transoms. Also, they were not designed to go much faster than mid to hi 60's.

X2

That boat works well with the seating that is in it... changing it will be costly and it won't work as well as it was designed because the cabin door is angled.

If you add a bunch more power you can see more speed but I would suggest doing that. They are depreciated to heck and adding 10-20k in engine work won't net you a dime on the back end. you are better of spending the dough on a faster/newer/whatever boat up front.

http://detroit.craigslist.org/okl/boa/1596376182.html

Here is a freshwater 88 Bravo boat that looks to have Merc 400's in it.

5K more he could be in my 90 hustler with 502's that runs mid 80's custome paint. 99% fresh water
-Mike