99 Mastercraft Sportstar

dillonC15dillonC15 Posts: 2
I have a 99 Mastercraft Sportstar that all of the sudden one of the wet exhaust hoses got to hot and melted through on the bottom side where it connects to the riser just past the riser. We originally thought the hose was bad and replaced the hose. We have also replaced the water pump. Why cannot figure out the problem. Any advice??


  • skihackerskihacker Posts: 507 Crazy Baller
    Sounds like poor water flow/volume, motor not overheating? There are 2 water pumps, intake and circulation, also very important no air leaks on the suction side of the intake pump.
  • Jody_SealJody_Seal Posts: 3,904 Mega Baller
    I see this a lot. 99 is nearly 25 years old. hard water scale, sand and rust clogs up the engine block as well as the exhaust manifolds and risers.
    thermostat housings as well as thermostat become clogged especially the bypass

    Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise.

  • paulpaul Posts: 63 Baller
    Agreed. Run some vinegar or dilute muriatic acid through the engine. I had ports in my 2002 that were completely blocked when I took off the heads.
  • dillonC15dillonC15 Posts: 2
    We have replaced both water pumps and thermostat was removed. The motor itself is not overheating. paul, what is the exact process of running the vinegar through the engine?
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