HyFive578

iTrader: (3)

I commented in another thread, but rather than completely hijack that one, I'll try to answer you here. The 525 is a solid 502 engine with a generally very reliable core. There are some weaknesses.

1) Valve springs: The combination of low installed height and low seat pressure are believed to cause instability in the valve train leading to a) spring failure, b) rocker failure, c) possible reversion. Look for unusual rocker wear: Remove your valve covers and look closely at the trunnion of the rocker and look for any wear (loss of the yellow anodized coating) around the poly lock. Any evidence of that indicates that the valve is moving around and is putting sideways load on the rocker... next possible thing to happen is the retainer clip breaks and needle bearings get spit out everywhere...

2) Rocker arms: Some very reputable engine guys believe the Crane rocker arms used have a limited life span.. around 200 hours. This could very well be related to #1..

3) Headers: This is not a fault with the engine. There are countless occurrences of header failures on the 525/600/700 series motors due to past issues in the manufacturing process of the headers for these engines. Pressure testing them often mitigates some of this risk as does flushing them religiously after every use whether in salt water or not and also draining them after they cool down.

4) Reversion: The 525 has an aggressive cam and is on the verge of reverting at idle. Pair this situation with an exhaust configuration like Silent Choice that puts the water into the exhaust stream near the collector and you get reversion.

I've owned five 525EFI engines. Any of the problems I've had have all been exhaust related and not the core of the engine. Even with the issues I've had, I love them. Last summer, I put over 100 hours on my boat and every time I turned the key, they fired right up. They are easy to get parts for and straight forward to fix when needed but they need care. Be good to them and they will be good to you.

thirdchildhood

iTrader: (6)

Yes, they exist. The top end service is checking leak-down and if OK then replacing valve springs, retainers and keepers and inspecting other parts. My mechanic put a flexible video scope in each cyld and all looked fine. Springs and retainers at 350 hours is hardly a tight maintenance schedule. Mine is a 2007 vintage engine that has some factory upgrades.

airjunky

iTrader: (2)

Hyfive summed that up nicely ,and the new stainless (semi stainless ?) Roller rockers seem to hold well on the BBC
I have nothing against the ls motors but a supercharged intercooled catalyst small block dollar for dollar
Holds plenty of potential for nasty expensive suprises too .if you happen to have one of those and you don't have a sea strainer better get one before your next outing

Patience...myass

Keep them maintained, do the top ends at 300 hrs, check the headers and you won't have a problem. I have 350 hrs on mine and they have been perfect.

imartin

Thx all, especially hifive578 for the detailed summary. Patience , u have 350 hrs on urs, what yr model and did u do top end at 300 hrs? If so, how did urs look and what did u do?

Patience...myass

I have an 03 353 Fastech. I am having the top ends done now by Eddie Young and it was time. The fire rings in the head gaskets were shot and the springs only had 105 psi seat pressure. We decided to go ahead and change the rocker arms too while it was apart.

On Time

525s here with 330 trouble free original hours. No repairs of any kind just routine maintenance. Along with winterizing had compression and leakdown done and perfect results fully in spec.

On Time

I always drain my headers and remove every blue plug I can reach each winter since 2006. Who did your header work?

Unlimited jd

iTrader: (5)

If you do the top ends RIGHT at 200-250 hours you can make it to 600 hours before needing to go back through them, and at that point the rings will most likely be pretty loose and bearings worn a bit. Just my opinion based on the valvetrain parts I've seen and used.
By doing them right I mean new valves that aren't stock gm crap, a real valve spring at a proper height and installed seat pressure, new rocker arms, new lifters and good pushrods.

imartin

ah, great to hear! presume you would rate your rpm ranges as normal, not lots of hours above 4500 or 5000? As for the header work, Shogren in Chicago (now Pier 57) did it per the Merc recall for the original owner. I am the 2nd owner. Beautiful work. I will drain all blue plugs. Thx!