I spoke with an independent Merc mechanic today and he told me that with these engines' hours & usage, compression will be fine if its able to pull 5200 rpm (and reach top speed) during the sea trial. He also told me the CMI headers on the Fountain should be fine if it was fresh water only based on his experience.

He "could" be right, but I think that's bad advice. My boat had great compression and pulled 5300 on the sea trial but one engine still had two cylinders with leakdowns higher than the others. Is that a problem. no, but it is something to keep an eye on and I am more informed of what I have.

As for the headers, that's just dead wrong or his experience does not include a 525 header failure. if the boat is a 2005, the headers are 2004 vintage and were made before CMI improved the design for Merc. Saltwater is a contributor but the bigger factors in 525 header failures are heat cycles and vibration. Whether in salt or not, if those headers were EVER heated more than normal operation temps, (ie: sea pump failure, blockage, anything to interrupt water flow), they could be susceptible to cracking at the welds. There are lots of 525 headers that have never had a problem and there also many that have failed at or before the hours you've indicated here. And if they're leaking and you don't know it, you are looking at a stuck valve at best, at worst, a catastrophic failure of the engine. If you pressure test the headers and there are leaks, they usually can be easily welded and you can enjoy the season.

Its your money, but neither of these tests are more than a few hundred bucks and could save you many thousands of dollars and hours of misery.

The headers need to be checked. It's not really an option with 525's, it needs to be done annually. I've had 2 gen x headers leak, which is the newest header out. Oh yeah and my boat is non staggered and boat in fresh water.

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This is just one of the things that can happen when those headers leak... convinced yet??

The advice from OSO is all spot on and from experience. I purchased a 525 boat knowing all the pros and cons after doing extensive reading on OSO. Sent my headers with 280 hours to CMI for inspection and re-polishing, it was a couple hundred bucks. No issues, the previous owner never ran the boat hard so he did not do it. Figured he would be ok, he was lucky. Heat, vibration and age fatigue the metal, it's part of ownership. 250-300 Hrs do top end refresh (at that time I also did lifters, pushrods and full rocker inspection). Over do all the proper maintenance, change impellers with housings often, and inspect the engines religiously. Keeping the temps down is very important with these engines/headers.

It's easy to pressure test the headers at home for free.

http://i763.photobucket.com/albums/x...s241Medium.jpg

Couldn't agree more. 525's are great, reliable engines if you give them the care and attention they need, especially the cooling systems. Most of the regular maintenance is pretty easy. I change my oil and filters religiously every 25 hours and sea water pumps at least twice a season unless sand or other foreign objects get sucked up in there, in which case, I change immediately (which happened to me this past weekend actually).. Nothing is worse for those headers than overheating..

Like to see more on how to test at home?

Have to get a little creative. I plug off one end then rig up a fitting for a water hose on the other end. Turn on the hose and watch for leaks. City water will be more pressure than the header ever sees

even with low hours I would do the springs, when a engine sits for long period of time 1/3 of the springs are compressed and that kills them as quick as running time...on our engines back off valve adj if going to sit for a long time...