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Thread: Merc best 2,5's

  1. #1
    ToffenG
    Hi!
    After this season I will convert from a single Promax 300 SVS to a twin Merc 2.5's. It proved to be too heavy to hang two PM 300 SVS on my ol' Phantom. The boat builder advised strongly two 2.5's due to the balance of the setup.
    A guy in UK runs a similar boat with twin Merc 2.5 SS (280 HP and 15 inch mids) engines, and top speed is in the upper 90-ties.
    I do not know so much about the Merc 2.5 other than one is 260 HP and one 280 HP. I am looking for the best version into longvity, and the possibility to tweak to 300 HP.
    If I am correct the brucato PCU can not be used on latest version of Merc 2.5 (280 HP). Is is easy to change the electronics into 260 version, allowing the use of the PCU? Can SVS Intake be used on the new version 2.5?
    Or should I go for a Merc 2.5 (260 HP), add a SVS Intake and a PCU? I presume I need a new alternator then?
    Down to basic. Which is the best engine? Max rpms should be 7500.
    Cheeeers and thanks,
    Toffen G

  2. #2
    STV_Keith
    Well, there is more info about this kind of stuff over at http://www.screamandfly.com , but the general concensus is:
    The 260's run hard, and can be modified to 300+hp. SVS is available, as is the Brucato PCU for tuning. Standard 16amp charging system.
    The 280's run harder, but have the 40 amp charging system with the big external alternator, and have a rev limiter built in at 7850 I believe.
    The 300 Drag's make 300+hp stock, but won't live as long. They will turn up to 10,000rpm and above though, in stock form.

  3. #3
    Tom Brown
    I haven't changed the fuel curve on a 2.5 but am about to. From what I read, it isn't something that is 'easy' to do, although the Brucato PCU looks to be the easiest.
    Also, I think the benefits of moving away from the stock computer go up as you modify the engine. My engine has been heavily cut so I'm hoping to make it run better with Wayne Taylor's MAD EFI system.

  4. #4
    randy77zt
    i think the last 260's were made in 97 or 98.all 280's after that.the 280's have a charging system.the offshore race version has a higher rev limit in the ecm.2 stock 280's with good props and set up should work fine.if you can find a pair of motors that counter rotate.check the mercury website for specs.

  5. #5
    W. Tripp
    New 260's are no longer available complete from Mercury, but rotators and Drop-ons are.
    The 280 is a great engine with the standard 7700 rpm rev limit, the Offshore Race limit 8250 rpm or with the limiter removed for up to 8700+ rpm. And the charging system is a great addition. If you want more rpm than this, only then would I recommend going to 260/Drag electronics. The 280 comes with more compression than the 260 ever did. The SVS will not work with the standard 280 since it doesn't have provisions for a throttle position sensor. If you convert to 260 electronics, the SVS will work well, as will the Brucato PCU.
    If you are interested in buying complete new engines - act fast. The 280 will be going out of production this summer.
    I hope this helps,

  6. #6
    STV_Keith
    Wayne, what else did they do in the 280's to allow those to run more compression without the detonation problems compared to a 260?

  7. #7
    W. Tripp
    The 280 is basically the Drag engine block with 260 sleeves. The port timing is mid range for the 260 and not as high as some of the later 260's. The block has the same improved exhaust chest as the Drag engine but without all of the hand blending and matching. The heads use an o-ring in place of a composite gasket, just like the 2001 and later Drag engines. The ECU map also runs a bit richer at part throttle. The 280 Race Offshore has a better map for performance use as it is a bit leaner in the low to mid range. Rapair uses this map when they pull the limiter.
    I have seen good running lake used 280's with over 160 psi from the factory that have run several seasons on pump gas without any detonation. It is my belief that the improved exhaust chest and o-ringed heads allow the 280 combustion chamber to run quite a bit cooler than the 260's and get away with more compression.
    Despite claims to the contrary, a 260 cannot be ported to Drag specs due to the exhaust chest changes - the 260 is NOT the same block, and is missing some of the material needed.
    I hope this helps.

  8. #8
    HavasuDreamin'
    Originally posted by W. Tripp
    If you are interested in buying complete new engines - act fast. The 280 will be going out of production this summer.
    Say it aint so.

  9. #9
    W. Tripp
    The S3000 is gone, the 280 will be gone in just a few months, and the Drag is scheduled for termination next summer.
    A 245 hp direct injected 2.5L will be the new "High Performance" engine with a proposed 7700 prm limit. Think of a 200SX with more rpm.
    The EPA has told the manufacturers that any engine that shifts out of forward gear is NOT a race engine - the days of Mercury 2-stroke performance are numbered.

  10. #10
    HavasuDreamin'
    Well if this isn't the most depressing thread I have read in a long time. I read about Merc's new 4-stroke in the most recent issue of the magazine. I have to say that I am impressed, but at 667 lbs., the transom life of a 19' tunnel has to be next to nil. Also, they mention low end hole shot and mid range a lot which we all know means no 7,500 rpm passes.
    On the bright side, there were so many 2.5L motors made from 1992 - 2004 that Merc will have to carry parts and drop ons for a while I would guess. It shouldn't be hard to put one together even after new production has stopped.
    HD

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