Ok -2006 35ZR w/525's worth? vs a 2007 35ZR with pair of 496's lets say same condition with same hours what would you say the difference would be on these two boats ? Thanks

25~30K Plus any difference in drives also

closed cooling ?

Not sure on price but night and day difference in the fun department.

496's boat does 82 mph 525's >94 mph

I was just in this decision making process and one thing I found was that pretty much all 525 boats on the market were ready for the top end regularly scheduled maintenance. Not a bad thing but it seemed like few on the market reflected the money you're about to have to spend.

Loving my 496 boat! I'm sure the 525s would be really wild but I'm pretty happy with the 496s.

That seems like a lot for a 10 year old boat, I would think 15k - 18k would be more realistic.
It is all about how bad the buyer wants said boat.

I'd say it depends. Probably 10-25k depending on what exactly has been to the 525EFI boat.

525EFI's with 350hrs and never been opened are going need prob 10-12k+ worth of maintenance soon.
496's with 350 hrs will need nothing for a long time.

I think the biggest thing is when considering a boat with these engines is to get a computer print out of the run history. This in my opinion is one of the best things anyone can do. A boat that has a run history of being at 3,500 rpms most of its life verses 5,000 rpms or the rev limiter is going to need less work, if any, earlier on than the other.

The 525 EFI is a great motor, but besides the normal maintenance schedule on them, there are also known CMI header problems on a lot of these boats. I would thoroughly check out the CMI headers for any issues on any 525 boat that you are considering. Many 525 owners have had expensive CMI header repairs/replacement (myself included). The CMI headers are the weakest link on the 525 boats IMO. Only you can decide if the extra performance/speed is worth the extra expense and maintenance that you will have to endure...