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Thread: 496 w Merc SC blower Need help

  1. #1
    ghittner
    Building a 496 out of 454 block. Merlin heads, H beam rods, roller 612 lift cam 114 deg. Bought a blower supposedly off a 525 SC. Weiand, black case red Mercruiser SC insignia on side. I believe to be a 177, has single Dominator top. Is it gonna produce enough for this motor or do I need a 250 blower or........ :220v: ????? Help Please!

  2. #2
    C-2
    Bump
    Somebody, anybody, am also curious about this...

  3. #3
    paradigm shift
    Really depends on what kind of power you are looking to build. Need more info. I am no expert but I believe bigger is almost always better. Turn-em slower build less heat. Just my .02

  4. #4
    bigkatboat
    Get an 8-71 with 2X 850, and get 7/8lbs of boost. Intercool if you need more power.

  5. #5
    ghittner
    Ok, here's what I've found so far. A 250 or 256 depending on the manufacturer..... Is about the smallest I want to run to build any decent boost (over3-4 pds) on my 496. The 250/256 series require no modification to the stock pulley system and will run independently of the stock belts on my 1989 Mk4 series Merc system. This will fit under my stock hatch cover and is the most simple system to add. Its approx 2" shorter than 671 systems and 671's require using different belt/drive configurations. I'm hoping to get 5-8 Pds of boost and there are different pulley diameters to choose from to adjust the boost. I'll be going with the Weiand 256 system. Hope this helps.

  6. #6
    Havasu Hangin'
    My 250's can make 6-8lbs of boost on my 509's (intercooled).

  7. #7
    Huffer
    Running A 496 Also,had A 420 Mega Blower,sold It Last Year Put A 14-71 Little Field With Intercooler Boy World Of Difference!bigger The Better,less You Have Ti Turn Build Less Heat!

  8. #8
    ghittner
    Hey Havasu Hangin, Thanks for confirming my thoughts here. Are you happy with your 250's? How long have you been runnin' em? Any problems so far?What make are they? What size upper pulley do you have? Stock ones?

  9. #9
    Havasu Hangin'
    Hey Havasu Hangin, Thanks for confirming my thoughts here. Are you happy with your 250's? How long have you been runnin' em? Any problems so far?What make are they? What size upper pulley do you have? Stock ones?
    They are B&M and they were on the boat when I bought it a couple years ago. I had them rebuilt last year, and it turned out one of them was about to go south (gears were out of tolorance). I don't think they had ever been rebuilt before.
    They are very low maintenance, and belts are easy to change. I have two sets of pulleys, but I can't remember what size (they are with the boat in storage). I believe the stockers make 6lbs.
    The biggest difference that I notice between mine and bigger blowers is where the boost comes in. The bigger blowers make boost lower in the RPM range...but that's not really what I'm after (don't want to kill my drives with alot of low-end torque). On the big end...6lbs after the intercoolers is fine by me.

  10. #10
    Mr Twister
    I am no expert on blowers but I do own a Checkmate with a 525 SC. That blower IS a Weiand 177. Weiand recommended that blower for 454 and 502 applications, it is a small blower so you have to spin it faster to make reasonable boost levels. When originally installed on the Merc package it made 5.5 pounds of boost w/o an intercooler on a 454 (a 496 it will be less). It would be probably be a bad idea to up the boost without adding an intercooler as the engine requires 92 octane fuel minimum with conservative timing. My engine runs really well but I'm going to freshen the heads in the spring. Download the blower instruction manual from the weiand website for more details. BTW those engines were derived fron the HP420's of the era.

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