1989 26’ Predator

Discussion in 'General Conversation' started by Jonnydime, Sep 7, 2021.

  1. Jonnydime

    Jonnydime Active Member

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    What is the max safe rpm while running off a garden hose (60psi 3/4" hose off of the main supply line)? Just trying to verify if the tach will go above 4k without putting the boat in the water.
     
  2. KC_Jones

    KC_Jones Member

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    Idle is roughly the safest RPM off a hose. Any more than that and the raw water pump is flowing more than any garden hose can supply. WOT testing should be done on the water and under load. Hitting a wall at 4k is entirely possible, it's what boats can do when set up properly.
     
  3. Jonnydime

    Jonnydime Active Member

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    Looks like I’m going to the lake this weekend.
     
  4. Mistress

    Mistress Well-Known Member Staff Member Supporting Captain

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    FWIW, 60 psi is a good way to break a strainer. Best to keep the seacock open when on the hose or use a bucket to draw from.

    And the seawater pump at rpm will draw more than what your hose can output.

    I know there's some calculators out there that disagree, but I haven't seen the garden hose yet that will fill a 32 gallon trash can in 1 minute.
     
    Last edited: Sep 11, 2021
  5. Ship

    Ship Well-Known Member Supporting Captain

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    The 383 might be rated for anywhere between 4800 and 5000 rpms at wot. A Dyno test may have been done if a pro rebuild or if a factory 383 the max rpm would have been part of the paperwork. Before wot testing verify the tach readings. With the right prop on the boat, it should reach the speced rpm. That is the best set up for the engine. You can fiddle with the prop and hull conditions but at a price.
     
  6. Jonnydime

    Jonnydime Active Member

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    I verified that the tach is accurate with my hand held. So when the previous owner bought this boat it had a Holley efi setup on the 383 and he had issues while trolling and replaced it with a 600cfm Edelbrock carb. I think I’m out of fuel on the top end. Before anyone ask it is definitely a 383 as it’s externally balanced.
     
    Last edited: Sep 11, 2021
  7. Mistress

    Mistress Well-Known Member Staff Member Supporting Captain

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    600 cfm should be plenty.

    What's your advance curve look like?
     
  8. Jonnydime

    Jonnydime Active Member

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    It came with one of these so I don’t really know I’ll have to get a timing light on to check total advance. It runs good it just runs out of steam around 4000 to 4200rpm.
    https://performancedistributors.com/product/chevrolet-marine-dui/
     
  9. Mistress

    Mistress Well-Known Member Staff Member Supporting Captain

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    I'm wondering if there's a mismatch from what a TBI engine DUI expects vs. a carb'd engine.
     
  10. Jonnydime

    Jonnydime Active Member

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    The previous owner put the dui distributor in when he converted to the carb. It had an early Holley mpi system is what he said. 600 cfm just seems small for large displacement small block but then again I’m used to big block Ford stuff.
     

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