bob_t

I do not remember what the Merc blowoff valve was set for, but it was somewhere around 35 psi. I'm sure someone else will know the exact number.

breakitout

Bob T thanks for the write-up.. exactly what I was looking for Anyone who has anything to add feel free.
Does the 575 need 93+ or 91+ octane? Premium is scarce at marinas up here so will have to avoid that motor probably.

I like the idea of the 525 I heard that you can send your headers back to CMI for re-working for a very reasonable cost... a good way to make that setup more reliable?

Irishtornado

Most of the parts for these engines are available through...

http://www.mercruiserparts.com/selec...asp?type_id=8H

endeavour32

iTrader: (4)

From what I understand you can send the headers back for repair for I believe $150 a side. BUT you still have the lower quality stainless.... If is was me, I would sell the Merc headers and replace with something better!

SDFever

I believe this is the first person that has posted the 525 header problem correctly.

At least as far as I can remember reading... He's right.

Steve Zuckerman

The stock motor has low boost (4PSI), low compression (7.5:1), and is tuned very rich. Shouldn't be any problem running 91. It also has a knock sensor that pulls timing if it detects knocking.
I'm running 8PSI with a 871, 8.75 compression, 93 octane, no issues (twice the boost, 1.25+ CR). I have run low on gas and mixed 93 with 89 dock gas. Not my preferred way to go, but it beats running out of gas, and getting towed in. I just stay out of boost range and run part throttle.
BTW, when it comes to selling or buying most performance boats, they usually carry better retail with blue motors. Insurance is easier too. They are listed in Kelly Blue book. Ilmor may be? Aftermarket, probably not.
Regards,
Steve

breakitout

hey Bob T another question for you... what type and weight of oil do you run in your 525? Anyone else who has suggestions please throw them out there. I take great care about what type and weight of oil to put in an engine.
I.e. should I run 20-50 synthetic (amsoil or mobil1) or is it better to run conventional oil and change it frequently?
Plan on doing changes at no more then 25 hour intervals.

thirdchildhood

iTrader: (6)

The 525 EFI is a great motor. The block is CNC machined, it has steel H-beam rods, forged pistons, aluminum heads, top quality valve train components, the hottest cam of any N/A Mercury Racing engine, Cometic head gaskets (later models) and on and on. Mine is an '07 vintage and still has the factory seal in place. No header problems here but I may have an "improved" version. It will burn the cheapest gas available without problem. It is an extremely popular motor and I recommend it. The oil issue is very complicated and everyone has their opinion on that so after reading a crap load of oil threads I decided to play it safe and use the 25w40 Quicksilver oil recommended by Mercury. I change it 3 times per season; About every 20 hours. I change it at the end of the season and run it on the hose so that it is stored with clean oil coating the parts. It needs a top end rebuild at about 200 hours partly because of the high valve lift and beating that the valve train takes. It also sounds very cool. Here's mine. BTW, it has full Zeiger steering now . http://www.youtube.com/watch?v=i7H6zNFH8f0

breakitout

with my SBC motors I do the oil changes like you have , just regular quiksilver 25-40 about 25 hour intervals. But w/ 525 I want to give it the best treatment possible. Also it will be used motor so is it advisable to switch to synthetic?

thirdchildhood

iTrader: (6)

Here is my take: For years full synthetic was a strict no no because it was too slippery and could cause the roller lifters to skid on the cam. Now that Bob Teague is sponsored by Amsoil it is magically OK to run full synthetic. I'm still not convinced. I'm sticking with 25w40 Quicksilver which is what the Mercury service manual for the 525 calls for. You will get a lot of different answers if you ask what oil to use. Hang on!