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How Long Is Too Long At WOT?

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  • #31
    Originally posted by 82rude View Post
    Mercury marine went approx. 50,000 miles all out on lake x in the late 50,s?Even filled up on the run!75 HP 2 STROKE https://vimeo.com/5370345
    Those were 2 strokes. and those engines needed lots of pampering, and some outright cheating to make it looked like they made the 50,000. Oh 50,000 miles was run, but the original powerheads that started the run, weren't the ones crossing the finish line. Complete sets of pistons, crankshafts, even complete powerheads were changed on the sly.

    the book Iron Fist has a chapter devoted to Operation Atlas, and tells of the shenanigans that happened

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    • #32
      OK, then drive it like you rent it.
      Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

      1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

      Past Boats
      1970 Wooster Hellion - Merc 9.8
      2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
      1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

      What’s behind you doesn’t matter.Enzo Ferrari

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      • #33
        Originally posted by TyeeMan View Post
        oiling in most outdrives is the limiting factor, as they were designed for the 5000 RPM limit of most motors

        That is a very interesting comment that I never would have given a thought to. So if you want to turn an outdrive faster how does one do that? Oil pump, pressure lubrication?
        Add a drive shower first, just for cooling. But you really need a Merc Racing drive of some ilk for sustained 5000+ rpm.
        2002 Bryant 188 4.3MPI

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        • #34
          Sign up today
          Originally posted by REDRIG View Post
          Crap , I thought you were supposed to run at WOT as often as possible.

          I have ran mine for probably an hour straight in the low 4s .

          I boat at a huge lake (Powell) and when we get glass I can make some good distance in one run . Of course keeping an eye on temp and listening for any changes. Looks like I will have to change that strategy and do some putting along the way.
          I guess I should preface this to say, the OP wasn't talking about racing engines or drives.......


          There's probably a couple of things to keep in mind when running any stock I/O at WOT

          At Lake Powell for example, you're at approx 4000ft MSL AND if it's 100ºF your density altitude is about 7000ft. (and it's frequently hotter)

          You lose approx 3.5% power per 1000ft of density altitude, so your 175hp 302 is only really (if in perfect trim, RPM, tune etc) capable of producing somewhere around 130hp.

          Even if you "prop" for maximum recommended RPM, (and you're not turbo or super-charged) you're not even capable of producing 100% sea level HP

          So, running it at "WOT" all day is no problem. If you haven't jetted the carb for the higher altitude, it'll run a little rich and burn a little more fuel and might even foul the plugs, but it won't hurt to do it ALL DAY LONG.

          Aircraft engines (like marine engines:high cu-in, low compression, slow turning) do this all the time......... once you get to around 4000 MSL or so (and you have an adjustable pitch propeller) the throttle is likely already at WOT and will stay there until TOD (top of descent) (hours)

          Most marine engines are not configured to produce the kind of maximum power (their automotive counterparts are capable of) The engines *could* do it if allowed to turn faster and Most SBC's and SBF's can produce a LOT more power but are compression & RPM limited (for "regular" I/O operation like indicated above) So the engines by design are already "de-tuned" (due to low compression, cam design and max RPM etc)

          Running them at WOT isn't going to "hurt" them. You'll still use more fuel than you will at "cruising" RPM and speeds, and you'll wear out the engine a little quicker than if you never ran it at WOT but I don't think anyone will get there.

          This is sort of like the oil argument. You're not going to damage most marine engines from running at WOT (or using the "wrong" oil) before they fail for some other far more common reason like freeze damage, submersion, exhaust reversion, or neglect.


          Cheers,


          Rick



          Last edited by HT32BSX115; January 11th, 2019, 12:54 PM.
          1987 FourWinns 211 Liberator, Originally an OMC 460 King Cobra.
          Re-powered in 2006 with a 1997 Mercruiser 7.4L Bravo III

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