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  1. #1
    Piston? WHAT Piston?!? JGringo's Avatar
    Join Date
    May 2007
    Brookfield, WI/ Des Moine, Iowa/ Houghton, MI

    Anyone got an MRD Injection for a 780 engine?

    I know this doesn't belong here, but this site is really confusing now,

    I was wondering if anyone had an MRD F.I. system they might want to sell for a 780.

    If you know anyone, please let me know.

  2. #2
    john zigler's Avatar
    Join Date
    Aug 2006
    jeff, i have access to a brand new MRD for a fuji.

    give me a call at the shop, and i can get you a price.

  3. #3
    Connecticut CrazyA's Avatar
    Join Date
    Nov 2005
    How mrd fuel injection works in watercraft
    mechanical fuel injection is simple and easily adjusted once you
    understand how it operates, there are three main components:

    #1 crank driven fuel pump

    #2 metering valve (barrel valve)

    #3 throttle body
    when the engine is running fuel is delivered to the metering valve by the fuel pump, which is turning the same rpm as the crank therefore if rpm is low fuel pressure is low. If rpm is high fuel pressure is high.because fuel pressure rises and falls with engine rpm and the metering valve increases and decreases fuel pressure to the to the nozzles according to butterfly position in throttle body. This provides a smooth and precise fuel curve which means instant throttle pull through the entire rpm range nozzles must be correct size for system to operate and respond to adjustment. Nozzle size is determined by total cc of engine level of modification, size of throttle body 46mm or 50mm. Each injection system leaves mrd with correct nozzle size for use on full modified engines t-valve : This is an overall adjustment, it's range is closed to 3 turns open. Closed is rich, open is lean (opposite of carb t-valve.)most engines will tune by adjusting this one adjustment. Some require other fine tuning.caution : Never disconnect arm from brass metering valve barrel valve)it is precisely set adjustments are made by loosening jam nuts and rotating center hex piece, extending eyes of link richens, shortening distance between eyes lens throttle leans. Maximum adjustment controls mixture in free rev, conditions experienced in choppy water, when boat comes out of water with throttle wide open, two things happen!

    #1. Load comes off engine
    #2.fuel pump is driven faster pumping more fuel than is needed. To cure this we use a pop off valve to maintain proper fuel pressure for full load conditions (flat water) and relieve excess pressure not needed. Range is 14 psi to 16 psi. Never use any other filter other than the screen supplied in the kit from mrd.

    #1. Engine runs clean with t-valve closed therefore nozzles are too small
    #2. T-valve has to be open more than 3 turns for engine to run clean therefore nozzles are too big.
    #3 engine runs rich only in choppy water therefore pop off is too high.
    #4. Engine leans out or power fades on long runs on flat water means that pop off is too low or t-valve open too far.
    #5. Engine has good top end pull but loads up on bottom-adjust heim link to shorter length. #6. Adjust injector based on engine performance not plug color.

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