425 hour 525's
 

I just bought a boat with 425 hours on 525s. Was told top ends where freshened at 225 hours. We did leak down test and is perfect and pressure tested headers are still tight. I figured I would do valve springs and lifters for sure this winter but what are your guys thoughts of bottom ends with 425 hours on them? Oil pressure is good and no use of oil. Also should I be worried about headers with them hours on? They are original and in staggered fresh water boat.

Leak down and oil psi good? 5k per engine bottom end. You have 2 choices. Spend 10k or don't. My vote is don't. Pull valve covers and intakes. Try to see if head gaskets are new or orig. 525's like to pop head gaskets. A full real valve job would be preferrable to replacing the springs. Might wanna just replace the heads with an upgrade since most shops charge 3 to 400 for cleaning up seats and guIdes. And with heads off you can get a pretty good idea of what the bottom ends look like.

I'm new here but not new to racing engines. On top of compression and leakdown tests, every time I buy a boat or vehicle with a used performance engine I change the oil and send samples to Apex Labs to establish a baseline and see if anything is really out of whack. If an engine is worn, you will see out-of-band readings in the oil. You can then run a few hours on new oil and sample again to compare/confirm, but at least you'll have another data point that you might be dealing with a rebuild or repair situation. I just bought a Formula 353 with 525SCs and sent the oil off for testing. The results were entirely consistent with the maintenance records and what the seller said about the engines; no abnormal readings or cause for concern. Prior to that I looked at an immaculate 32 Fever that I was absolutely in love with but the oil didn't look or feel as fresh as being 20 hours old as the seller had represented. He was gracious enough to let me drop/replace both filters and take oil samples. Both engines had a ton of bearing material in the samples and TBN values indicated the oil was well beyond spent. The seller blamed it on his service shop not doing the appropriate work and I had to pass on the boat.

Who is making aftermarket heads that work with header bolt pattern that 525's have?

I'm with d&k on the bearings. Lot depends on routine maintenance etc and how hard the boat was run. Over the many years of boating my time was pretty consistent btwn 400-500 tops. On the flip side I've run with guys who go well over 1,000 hours.

Nobody makes them you just redrill the header flange. Only a couple holes. You said staggered. Did they make a staggered fastech?

that 3/8's header flange is a PITA to drill through.........4 holes on each header

Drill the heads much easier. I did 4 heads in an hour last week.

Do a scan. When I scanned mine almost all the hours were at idle or very low speed.

I bought 42 Fountain executioner.

Thanks for all the info! I think I will pull them apart and have piece mind next season.

Have you scanned the ecu for run history? You might be supprised at how many of those 425 hrs were run at idle or below 3500 rpm. I too had the compression & leakdown test done before getting my 525's springs & lifters replaced @ 250 hrs and was happy at how healthy the engines were. If your 525s are maintained and not beaten on badly, I think they should go over 1000 hrs before needing a full rebuild. My old 454 mag efi was torn down just shy of 1000 hrs and the bottom end was rock solid. This forum is a great place to learn what's going on in the performance boating world, but I would suggest speaking with a Mercury Racing mechanic and getting his adivice on what to do with your 525s. Then go out and enjoy your boat worry free. Best of luck on what ever you decide.

I had a pair of 330's in an IMP with TRS's. the prev owner ran em hard, but took care of them. 1000 hrs. when I sold the boat, buyer had it at 72 mph. GPS. now, a 330 top end NEVER needs valve springs. but that is a different issue.