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Info on Merc's 525SC

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Old 09-23-2002, 01:42 PM
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I just put a 525SC in my boat w/a super chiller. I love it so far!! Awsome motor....And the whine those baby blowers make is KILLER!! Even with the super chiller I didn't need to cut the engine hatch. Motor starts no prob. idles no prob. not really any surge, I put GIL dry exhaust on it and it is loud as hell!!!....great motor! I did have it completely gone through prior to putting it in though.

Tank
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Old 09-23-2002, 02:40 PM
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Tank,

What did you have in there previously? And how much taller is the 525SC?

Where did you find the used motor? Where should I start looking for one?

Sorry for all the questions but I'm very interested in upgrading this winter.

Oh ya, what were your performance gains?

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Old 09-23-2002, 03:18 PM
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Since you guys are on the subject of 525sc's I have a few questions.
A friend of mine is looking at a couple of disassembled 525's , he is looking to make a little more power than the stock 525's and i made a few suggestions, what do you guys think ?

Upgrade the rods and rod bolts, maybe Eagle or Manely
Upgrade the heads, Brodix with mild porting
JE pistons, Do the Merc 454's have metric rings like the 502's ? that's my reason for changing
A custom ground cam to take advantage of the supercharger
add an intercooler.
Do you think these upgrades would be worth it ? He would like to make a honest 550hp
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Old 09-23-2002, 04:45 PM
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Quote:
Originally posted by DallasHeat
Tank,

What did you have in there previously? And how much taller is the 525SC?

Where did you find the used motor? Where should I start looking for one?

Sorry for all the questions but I'm very interested in upgrading this winter.

Oh ya, what were your performance gains?

DallasHeat
Dallas Heat,

I had a stock 454L motor (not the mag). My boat was over propped with that motor so I could get like 62-63 out of it on a good day. Now that was on Speedo, not gps so prob. realistically 58-59.

The 525 itself is the exact same highth as the 454 block. The little baby weind (sp?) blower isn't really that much higher (see the pic from griffs boat) and the super chiller is what? 4-5 inches maybe. My Baja has alot of freeboard so it was not a big deal. Fits right under there.

The motor came out of my friends 38 Scarab. He threw a rod through the side of the other motor (thanks to a leaking stelling header) and parted out what he could from it. Then put Teague 800's in and after letting the good motor sit for just under 2 years he gave me the motor (it pays to have good friends! ) The only prob. was water had sat in two of the cylinders while the motor sat. So I had it completely stripped down new EVERYTHING and bored out the block, milled the heads, new pistons, rings, water pump, alternator, etc, etc, etc. The mechanic said it should be making right under 650 HP. with an estimated speed of somewhere in the range of 80-85.

I've had it out and run it pretty hard but it is over propped right now with a 28" 4 blade. So I want to get a 26" 4 blade and see what happens. I'm only getting 5K out of the 28 and I need about 5500. My speedo is not working right so I don't really know the max speed but I can feel it is dam fast!!! I'm going to get the gps out there soon and see what kind of numbers I get out of it.

I couldn't tell you where you could find a used 525SC. Look on the board here in the motor section and also in the back of Power boat mag. Thats where I'd start.

Tank
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Old 09-23-2002, 04:51 PM
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Tank,

Great friend Thanks for all the good info.

I'm a lookin


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Old 09-23-2002, 05:09 PM
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Good luck bro...If I see one Ill let you know.

Tank
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Old 09-23-2002, 05:14 PM
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26Scarab, I don't think he would have to do that much to the engine to get an honest 550hp. Just add an intercooler and turn the boost up a # and it would be there.
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Old 09-23-2002, 05:35 PM
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blowers go out at 150 hours?!?..black thunder boat

I thought 525sc are strong as normally aspirated mercuries;
isnt it too early 150 hrs?
as I understand this engine is in
''always-take-care-of-me '' class

so why dont you buy a more hp generating engine with almost the same price?

just an idea...
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Old 09-23-2002, 05:38 PM
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Griff,
I know my friend won't have a problem with the intercooler but I know for a fact he doesn't want to increase the boost.
He is really concerned about reliablity issues, that is why he isn't building a bigger CI blower motor because then it would have more torque and will hurt drives.
My opinion would be to build some blown 540's and call it a day... he's got two engines , he can always get home !!
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Old 09-23-2002, 05:51 PM
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I was only saying to increase the boost from the stock 5# to 6#. I don't think this would create any problems. The only problem with spinning the 177 blower faster is that the heat created can overcome the gains from the boost. Thus the intercooler to keep the air charge temp down.

Adding just an intercooler without increasing boost will probably still get him to the 550hp. I'd check with Whipple and see what they say about HP gains with their intercooler. It is trick, but about twice the $$$$$ of a superchiller. Also, it only adds 1" to the overall height.
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