I am a new 525efi owner and have read many threads about the 525 needing top end rebuilds post 250hrs. This thread is to see if there are equal or more stories of 525efi ownership with hundreds of trouble free hours (with regular maintenance of course). To qualify, I am very easy on mine. 90% of all my hours under 3500 rpm. Thx.

Exhaust and water reversion seems to be worst than valve spring problems...

310 hrs no mechanical issues, couple of sensors went bad, headers pressure check good, top end service last year at 280 hrs. Replaced original mechanical fuel pumps as maintenance last year, 1 new pump lasted 1/2hr, not an engine problem. My ownership experience has been rewarding, some will have near the same feedback and others will get out the laundry list.

The headers have the "sweeping headers" recall warr work done. That hose removal and plug that needed to be done. I still wonder if I should unscrew that plug and drain the header for lay up periods....

Full service done, inc mechanical fuel pump, all the other stuff. My first summer is ahead of me as I picked her up late this season....

Times have changed and the 525 is for lack of a better term, an old motor these days. THere are a few companies getting over 525 out of small block LS motors, with greater durability, multi year warranty and at a fraction of the price.

I understand what your saying but out of all the Poker runs (5) we did last year and a few fun runs I saw 1, and only 1, boat with Ilmor 570s. That 353 Fastech factory boat was bought by someone out your way So Mi., nice boat, near same top speed as my 353 with 525s. 525s will be out there for awhile considering their long production run and shear quantity. Certainly not dinosaurs or an old motor, very relevant in fact because of today's market and so few "new" go fasts being built with the small block LS.

Keep up on maintenance such as top ends every 300hrs and pressure check headers every season and most I've read are loving them.

Theres very few new go fast boat being built period. The ones that are being built are getting big power. There are tons of the ls's out there in wakeboard boats etc. Indmar not only has the ls in 500+ hp, they are also doing the new ford SB, over 500 hp, with multiyear warranty. Ilmor indmar, mast. seven, marine power, pcm, gm powertrain.. pretty much everyone BUT merc is offering them.

True, merc solld a ton of 525's with headers spec'd to kill the motor as soon as the warranty expired even,,,,,,, It was a great motor......

Thought OP was asking about 525s that are in his performance boat and feedback from owners on their experience?

I'd be more worried about the junk that lives directly behind them