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Thread: Intro and a couple of Melroe M500 questions

  1. #1
    Probationary Member
    Join Date
    Jul 2014
    Weare NH

    Intro and a couple of Melroe M500 questions

    I've had my 65 Melroe for 3 or so years. Long story short the 23 hp Kohler is tired and impossible to find even head gaskets for. I made the last set from sheet copper. I found a nice 20 hp Onan which I just finished installing. I was able to use the OEM sheave drive but I won't be able to use the Cessna pump, It might be shot anyhow. The only specs my manual has on the pump state that it must produce 1600 psi. I'm wondering if I can use one from Northern tool that delivers 1600-3000 psi at 3 gpm. I've also found some Cessna style pumps with a keyed shaft.( I'll be mounting the pump just aft of the motor and driving it with a pulley). I have no idea what GPM rating I need. Also I have 2 manuals, one specifies ATF in the hydraulic system while the other states hydraulic oil. I've been using Tractor supply hydraulic oil and have had very jerky hydraulics. I'm wondering if using ATF would help that problem. BTW I've bled the system as best I can. Thanks for any advice.

  2. #2
    Senior Member
    Join Date
    Jan 2009
    Coos Bay, OR, USA
    Bobcat says 9 gallons per minute. Figure out how fast you'll be turning it wide open, 9gpm X 231 cubic inches is 2,079, divide 2,079 by the rpm to get the cubic inch displacement of the pump you need. 9gpm at 1,600 psi will pull about 8-1/2 horespower at full throttle.

  3. #3
    Senior Member CRAFT's Avatar
    Join Date
    Jan 2010
    100 M H,BC,Canada
    Welcome to the Forum Mike ..

    Just a small Heads up ! . If you thought getting Parts for the Kohler were hard to come by (you never mentioned the Model) . You better HOPE that the trouble you went thru with the Onan to fit in place, that it was a REALLY Good one (you didn't mention the model of that one either . LOL) .. Onan's Parts are Extinct ! .. the Company has not produced engines for a few Years now .. any parts that are around won't be for much longer . Cummins bought out Onan and shut down the engine operations, With the larger Garden Tractors that JD made back in the '80s and '90s they were all powered with Onans (mostly 18 & 20 hp) .. Those engines now are all clocking in around 1000-1400 hrs and are ALL blowing up .. so the GT guys are gobbling up any/all existing parts Just ask Me ! . I just re-powered my JD GT with a 23hp Kohler V-Twin because of this issue of Obsolete Onan engines, at least Kohler is a current USA company the Engine I used was a donor engine out of my 'ol Bandsaw mill (I re-powered with a 60hp VW Diesel), with over 5400hrs on the clock of the Mill ... (my Onan P218 had ~1250hrs, blew a rod, very common)

    Good-Luck ! . and enjoy HEF !

  4. #4
    Junior Member
    Join Date
    Oct 2013
    Massachusetts (not my fault.)
    I was a couple of hundred bucks into the Onan CCK 25hp (in my M444) when I finally made the smart decision to do away with it and go with the repower (after learning a $350 Zenith carb "might" fit my machine.) Anyway, I went with the Briggs Vanguard 18HP, and let me say, its nice turning the key and having her do what she's told on a daily basis.

    If your Onan has electronic ignition and runs tippity tops, go ahead and use it. But understand when that engine needs work, you're in for an uphill battle. I wish I went Briggs immediately. I'da saved myself a couple hundred bucks, several hours, foul language and burn marks on my arms.

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