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Thread: Mercury 70

  1. #31
    John (Taylor) Gabrowski
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    Default 3 Holer 2 Carb Merc or Mariner have the same repute as the Firenza was to cars! Junk

    I went through screwing with half a dozen of those 3 cylinder 2 carb blocks and 4 of them did that to the top cylinder destroying the piston and the head every time no matter how much extra cooling we fed in at different points or took out of others spots knowing it had that problem. The last two complete blocks (no carbs or ignitions) and all their spare long block parts (no carbs or ignitions either, they are worth something) from the other 4 went into metal recycling (my neighbors took them in and bought beer with the proceeds) this last spring as even the dealers didn't want them back even though they were overhauled and fresh!

    To begin with when I asked my marine dealer friends for these engines to test for FE, they thought I was nutz immediately. They told me I was wasting my time from square one. They gave me complete powerheads for free, take all I wanted!! They told me if a person wanted to loose customers you sold them a Merc or Mariner 65 3 Holer 2 Carb and they the customer would be back for warantee until it ran out which made them madder still and then you lost them as a customer permanently. They were that bad a motor! A very ill concieved deflector using dated technology well past its design use.

    One dealer had a complete Merc 3 holer with a for free sign laying by his inlet road for 3 years and no one took it! Finally a grader wrecked it when it tried to make it part of a snow bank clearing the road in winter!

    Enough said.

  2. #32
    Sam Cullis Mark75H's Avatar
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    Darn, I was asleep when I did that math, wasn't I?

    OK, the leaf blower can blow into the 49 ci motor, but it is still just going to blow out the exhaust ports. You will get may be a 5 hp power increase due to improved scavenging. About enough to justify carrying the leaf blower in the boat, but probably not enough to justify the 10 or 15 hp more gas that you will be using in the outboard alone.
    Since 1925, about 150 different racing outboards have been made.


  3. #33
    Sam Cullis Mark75H's Avatar
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    Quote Originally Posted by John Taylor View Post
    A very ill concieved deflector using dated technology well past its design use.
    Bad execution for sure, but the technology was not dated at that time. The 70 hp triple used Merc's "Direct Charge" deflector technology which was state of the art in its day.
    Since 1925, about 150 different racing outboards have been made.


  4. #34
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    it's guna dry out the bowl and Nose over

  5. #35
    Sam Cullis Mark75H's Avatar
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    It won't dry the bowl ... the fuel pressure is a function of crankcase pressure on motors with crankcase actuated fuel pumps. I thought the OMC's still used them.
    Since 1925, about 150 different racing outboards have been made.


  6. #36
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    Stinger 75 uses a vac pump, sst60,CC, electric pump, when the air speed gets to a certain point in the venturi the specific gravity goes out the window,

  7. #37
    Sam Cullis Mark75H's Avatar
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    I didn't know anyone was talking about SST60's

    Specific gravity doesn't enter into it.

    There are a lot of motors that have successfully used "blow thru" carb supercharging. Studebaker and Ford used it as far back as the 1950's. Lots of turbo applications used it in the 1970's
    Since 1925, about 150 different racing outboards have been made.


  8. #38
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    Studebaker 2 stroke no. step up the fuel volume. we could do a Demo with your Moda

  9. #39
    YARD BIRD
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    Default "Blow Through .......it blows".

    That method works, but it does NOTHING for fuel EFFICIENCY . The carb or injector feeding INTO the intake of the Supercharger can actually increase fuel efficiency , as well as make a big boost in power . I always liked the idea of a centrifugal supercharger or turbocharger which had an aircraft carburetor (adjustable fuel mixture ) mounted to the intake side of the charger, naturally having a pyrometer in the the exhaust to read the exhaust gas temp. And before someone complains that it's too complicated, NOTHING worthwhile is easy !

  10. #40
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    a power valve that closed the top of the exhaust window just before the intake windows closed on the up stroke, then you would have somethin.

    otherwise it's NOS, no pressure change inside to blow the charge out the exhaust.

    only with injection that this is true
    Specific gravity doesn't enter into it.

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