The 575's in question are 2002's with 170ish very hard hours on them. What does it cost to refreshen them and what all is involved? How many hours can you usually get on 575's before they need to be rebuilt?

I'm interested to see what's posted here. The 575 (I've got one too) is a very mild setup all things considered. What do you consider hard- WFO 90% of the 170 hrs?

I spend an est 85% at cruise, 5% max wfo and 10% idle. Are the motors showing that they are tired thru oil consumption or low compression? Is there a known amount of cycles the valve springs can take before they are considered fatigued and vulnerable. What else would be the driver- it's not like we are racing and after that last 1-2% in a pleasure boat.

It seems a lot of marine BB (BB for big block OR bulletin board) people are on the "freshen them in "x" hrs train, some may say 100, 200 or 500. If you think they need to be freshened often, can you qualify your answer (With something more than "cause that's how I make a living") Sorry in advance for the sarcasm.

The 575's in questions are in a 2002 Top Gun that was raced - the engines have spent 50% of their 170 hours at WOT.

Wow! That is some hard usage. That certainly makes me feel more confident about longevity on my 575 as yours are still going at 170hrs.

The boat and engines aren't mine yet - it's a boat that I am considering buying and I am trying to figure in the cost of rebuilding the engines.

A merc scan tool will verify how many hrs at what rpm range- should you want to check. Good luck.

I wouldn't worry about the bottem end unless compression or oil consumption are an issue. I would rebuild the top end though. Valves,springs,lifters,rockers if they're roller (I'm not sure of that motor, but I think they are).

We just finished freshening up three 575s for a friends Fountain I upgraded the cams and picked up the torque about 65ftlbs and 35 hp throughout the rpm range the engines were completely done with all new internals ,valvetrain and hydraulic roller. we also had the blowers gone through reworked the carbs stripped the paint to the bare metal and applied a custom paint to match the colors of the boat. If youd like ill give you more details as to all the parts and work performed just give me a call at 1-305-884-5368 Laz Mesa I can also give you the customers name and number for reference.

I would figure about 1500 to 1700 bucks. A friend of mine is doing his. Full valve job, block decked, new valve springs, heads shaved, 2 new pistons, barings gaskets etc.

I think your friend will be doing it again soon.