Bingo....

should have mentioned boat....new to me.... 270 hours on 525's if I buy it obvioulsy I should replace the headers.... and hope for 400 hours?? or do the top ends right away? I guess a leak down test would be in order?? Fak... I was assuming 500 hours before I had to touch them..:eekdrop:

One of my friends has almost 500 hrs and hasn't done nothing yet and they are still running strong

Mine have 460hrs on them. They still run very strong, compression test and leak down was great when I bought the boat last summer. They have year old Hardin marine headers on them. I'm going to do the top ends out of peace of mind but we put almost 20hrs on it after buying it at the end of July and they run great! The top gun gets 84-86mph WOT.

If they haven't been ran hard you should be good. Do a leakdown and compression test on the motors and have the headers pressure tested also before you buy. If you get boat I would replace headers or bare minimum have them pressure tested every year. My opinion they are the most reliable/best "blue" motor mercury has built.

+1... this is the best advice.. definitely compression and leakdown test, and pressure test the headers at least once a year and pull spark plugs periodically to check for evidence of water intrusion...

...completely agree.. putting the header issues aside, the 525 is a bulletproof motor..

At 250 hours or so, you need to replace valve springs and rocker arms only. You can do the top ends later or a complete rebuild.

I have 330 hrs on mine and no problems. I also have the original equip CMI headers with no issues. Victory Marine down here recommends at 350-400 hrs for top ends light to avg use or earlier for heavy use. Someone at Merc Racing when I called with this question said he had recently heard of a Formula cruiser with 800 hrs on 525's with nothing done still running strong.

X2!

Rebuilt both of mine at 400 hours after both sets of headers leaked into the cylinders. :mad: CMI Gen X headers now on as part of the rebuild.

At these rebuild prices it is hard to believe they are selling used 525's in the classifieds for 25K+ a pair........After you buy headers it really gets expensive.....Makes brand new bobtails look reasonable at 31K each! (Proboats.com)

I've had a bunch of 525's in the shop lately. None of them had more than 250 hours. One of them with 210 hours had 6 broken rocker arms. We were just going to replace the springs, retainers, locks and seals. However, there were needle bearing everywhere. We had to pull the engine, remove the intake and oil pan and find all of the needle bearings. Luckily,none made it to the pan. They did make it into the lifter valley. How none went past the cam I don't know. I couldn't believe it.

Another had 191 hours that broke a connecting rod and launched it out of the pan. We pulled the engine to find a 3" piece of rod in the bilge. Needless to say, it made a mess.

All of the others (5) required pulling the heads to change the head gaskets. They all had the composite gaskets and the gaskets were all going between every cylinder. The heads all had low spots between the combustion chambers that required surfacing the heads. None of them would have lasted much longer. All of these engines were pre 2005, so they didn't have Cometic head gaskets. Now, they were all in 2005 and 2006 boats, but the engines were pre 2005.

The ones that do have the Cometic head gaskets also required surfacing. The head gaskets made quite an indentation in the heads. The heads seem to be kind of soft.

The other thing is the springs. They are chicken chit. They only have about 120#'s on the seat. If you plan on running any rpm over stock, you better change the springs. We have been putting 10* retainers and locks in place of the stock 7*. With the stock 7* setup, the install height is extremely short (about 1.820). There really aren't any other springs out there that will go in place of the stock PAC springs, and they are just to light on the seat IMO. The 10* retainers and locks give an extra .100 of install height. That's open up the spring options tremendously. Then you can have a spring with a more realistic seat pressure.

Here are some pics of the carnage.
Eddie