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  1. #1

    Default 1998 DF70 Running Hot


    I bought this project 1998 Suzuki-Evinrude 70 hp with boat 4 months ago with a non working fuel pump-Did fix that with complete system,but my motor has been running hot after i first used it with running fuel pump system,it spit out water out the tell tale for 1 minute then stopped . So i assumed it could be the impeller is shot or the thermostat . Dropped the lower end.impeller looked OK,still flexible,but replaced with a water pump kit,everything except the housing.
    Replaced the thermostat & gasket, put back together,still no tell tale water showing,blew out the line . Found a thread on line that said blockage from corrosion since the water threaded port on side to flush is seized,can't unscrew even with vise grips-Man did this guy abuse this motor or what.

    So i dropped the lower end again, removed the thermostat.
    I rigged a 600 gph bilge pump up with hose connected to the water tube inside the motor,bought 5 gallons of 12% vinegar shipping from New York,put the pump,hose & 12v wire to my battery and recirculated it thru the exhaust/tell tale for 5 days with vinegar and went thru 2 batteries.
    Flushed it out then ran Simple green then water put it all back together,Got the tell tale working with the pump,so i started it up using it manually,but engine still running too hot to touch after 3 seconds.

    So its not just the lower end,Its both,Buying one of those laser digital thermometers,like doctors test your forehead for Covid-19, off harbor freight for $27 tomorrow to see how hot the engine is running,the Thermostat is for 50C/122% F,Its better than it was,but still too hot to touch the head by the spark plugs.

    My other concern is why isn't there enough flow coming from the lower end to produce a tel tale stream after replacing the impeller?
    I bought Suzuki lube,followed procedures,rotated the shaft clockwise,Perhaps i need a new metal housing too? have to buy a whole kit to get one,$90 just for the housing, or is it corrosion in the pick up tube below the cavitation plate? tried to remove the screws with impact driver,nope.

    So will try to run the motor again to see how hot it gets with the laser thermometer, but i need to find out why the water isn't flowing up to the tell tale as well,Should i replace the metal housing,to see if its warped? any ideas on how to proceed with blockages?

  2. #2
    Join Date
    Sep 2010

    Default Re: 1998 DF70 Running Hot

    Testing on a hose with muffs ?----Or in a bucket with water at least 6" above the impeller ?

  3. #3

    Default Re: 1998 DF70 Running Hot

    Quote Originally Posted by racerone View Post
    Testing on a hose with muffs ?----Or in a bucket with water at least 6" above the impeller ?
    I tried it both waters with hose muffs-not great and water trough with 40 gallons of water,however lately i have been using the 600 gph bilge pump with lower end removed to the tube to keep the water flowing out the tell tale,just ordered a gallon of marine flush Descaler from amazon,another try in a bucket to flush, Considering to replace the entire waterpump housing as well,costs $100,it looks original ,1998 but in good shape,hard to know what is the reason why the water isn't flowing up

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