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  1. #1

    Why no 2.5 liter 260/280/300XS?

    Sorry if this is a dumb question. . . but why doesn't Merc Racing build a 2.5 liter 260, 280, or 300XS? The 3.0 and 3.2 liter XS engines are powerful and efficient, but have rpm limitations and are about 100 lb heavier than the 2.5's. The 200XS saves fuel and is light, but doesn't have the power the 2.5 is proven to be capable of. It seems to me that a 280XS or the like would be the best of all worlds: light weight, fuel efficient, and powerful.

    Is it that the 260/280/300 don't have the lifespan that has become the expectation of today's users? Or perhaps the air compressor can't handle the rpm range that would be required?

    Mike

  2. #2
    Join Date
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    Probably a combo of many reasons. I have heard the 200xs 2.5L motors were 225+ hp. Pretty stout for a fuel miser. The compressors will not live long at 6500 or more r's. Fuel delivery is so lean and controlled, no way you can get away with the porting that makes the old motors so strong.

  3. #3
    Join Date
    Jul 2003
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    It isn't a problem of the compressors not handling the rpm, as the 200XS is spinning 8,000+ rpm very reliably on the SST200 tunnel boats. I don't know why the Gen 2 2.5 is only making 240hp at the crank when fitted with the Opti direct injection setup, but that is all we get from Mercury right now.

  4. #4
    Join Date
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    Sounds like a job for Dave Bush Racing!!!

  5. #5
    I know the compressors rob some power but I have to agree that mercury should be able to get 280hp out of a gen 2 2.5 if they got 280hp out of a 2.5 over 10 years ago. I really feel that a direct injected 2.5 making just at or just under 300 hp would sell. Mercury should also bump the 300xs up to 330hp I'll stop dreaming now

  6. #6
    Join Date
    Feb 2007
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    lily lake WI
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    1 word EPA

  7. #7
    Correct me if I'm wrong, but the block angle and displacement are the same. So, the port map of a 280 could be copied into a 200XS, though the fuel injection would have to be modified to match.

    After reading some spec's on the 200XS on Merc Racing's web site, they state the peak hp on the ROS version is at 6500-7000, whereas the SST is the same 200 hp but at 8000 rpm. There is some basic math involved here, but if the cylinder pressure is kept the same, but the rpm at peak moves up, then the hp goes up too. . IF the 200XS ROS really makes 225 hp AND the SST makes the same torque but 1500 rpm higher, then the SST version would make 275 hp. Lots of IF's, AND's, and BUT's there. . . but I can't imagine Merc making a race engine and not use the same porting they used on the 280 or similar. Then again, they clearly state the propshaft hp to be 200.

  8. #8
    Quote Originally Posted by Michael J Giesler View Post
    1 word EPA
    Mike! your grounded!
    2011-2013-2014
    Lake racer High points champ
    95 Allison xb2002comp 260 merc
    Lake boat
    2002 checkmate 21 pulsare 300xs
    12ft Lowe Jon 15 merc

  9. #9
    Quote Originally Posted by the Shocker View Post
    Mike! your grounded!
    Not sure about grounded, but definitely on the terrorist watch list now.

  10. #10
    Join Date
    Jul 2003
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    Discovery Bay, CA
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    Quote Originally Posted by engineermike View Post
    Correct me if I'm wrong, but the block angle and displacement are the same. So, the port map of a 280 could be copied into a 200XS, though the fuel injection would have to be modified to match.

    After reading some spec's on the 200XS on Merc Racing's web site, they state the peak hp on the ROS version is at 6500-7000, whereas the SST is the same 200 hp but at 8000 rpm. There is some basic math involved here, but if the cylinder pressure is kept the same, but the rpm at peak moves up, then the hp goes up too. . IF the 200XS ROS really makes 225 hp AND the SST makes the same torque but 1500 rpm higher, then the SST version would make 275 hp. Lots of IF's, AND's, and BUT's there. . . but I can't imagine Merc making a race engine and not use the same porting they used on the 280 or similar. Then again, they clearly state the propshaft hp to be 200.
    The only difference between the ROS and SST versions are the rev limiter settings in the computers. The ROS version is limited to 7,000 and the SST version is limited to 8,000. Chris Fairchild has had several of these motors on the dyno and they put out right around 240 at the crank. They aren't really gaining horsepower from 7,000 to 8,000 rpm as the torque curve is falling off past 7,000 - that's why they have the same horsepower rating.

  11. #11
    Join Date
    Feb 2007
    Location
    lily lake WI
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    2,087
    i think these motors are great i almost bought 1 last spring merc racing had a couple as drop on kits that Jimmy Helmsley help put together with Chris Fairchild for drag racers not one sold i kick my self in the butt for not getting 1 i wanted to race 1 in lake racer up here a blarneys but i i heard was your going to get crushed by everybody well you know what who cares it would have been fun trying somthing different and this is the future maybe merc will make a stroker 200xs with a little more power because let all face facts merc racing is only going to make 2.5 parts for a couple more years and guess what is everyone going to do

  12. #12
    Quote Originally Posted by Michael J Giesler View Post
    ...maybe merc will make a stroker 200xs with a little more power ...
    When they have proven port geometry that will make 280-300 hp on 2.5 liters, then there's no need to stroke it to get the extra power. If you're going to increase displacement, might as well build it out of the 3.0 that already exists.

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