Motor problem

Discussion in 'Bubba's Outboards' started by jgdishon, Aug 28, 2006.

  1. jgdishon

    jgdishon New Member

    Messages:
    62
    State:
    Snowville,Virgi
    I have replaced the water pump and rebuilt the carbs on my 1984 50 hp Mercury. I am pumping water with force now while ideling, but when I get up to speed it starts blowing steam and the motor seems to start skipping. I leaned over the back of the boat and it looks like the prop is bearly under the water. I have tried all the manual trim levels but it doesnt seen to make a diffrence. Off hand I would think I need a longer shaft on my engine, but it is a good 10-12 inches below my boat now. The water holes are under water. Any Suggestions?
     
  2. trnsmsn

    trnsmsn New Member

    Messages:
    1,214
    State:
    Missouri Originally Now I
    Did You Replace The Thermostat ?
     

  3. jgdishon

    jgdishon New Member

    Messages:
    62
    State:
    Snowville,Virgi
    Local Marina says My motor doesnt have a thermostat. Buty I did think about that.
     
  4. scout

    scout Member

    Messages:
    766
    State:
    Louisiana
    Hey Jeff. How did your boat run before you did the work to it? Also did you make sure that the water pump impeller blade veins were curved the right way when you installed it. Even if the blades were installed backwards you will get some water circulation at idle but not at running speed. At running speed the blades are folded back by the pressure of the water allowing the water to by-pass the impeller blades. If the impeller was installed backwards it will not work at high speeds. Hope this helps.
     
  5. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill


    Randell even if you installed them backwards they will right themselves on the start up of the engine.
     
  6. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill

    Jeff I am going to study the circulation of that motor and I'll get back to you in a little while.
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Jeffery the more I think about this the more I am leaning towards a exhaust leak into the cooling system and causing the steam or exhaust smoke mixed with steam. Either way it will have the same effect. I am still stydyinng the flow of it now.
     
  8. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Did you put a bead of silicone across the back of water pump area of the exhaust housing?
     
  9. jgdishon

    jgdishon New Member

    Messages:
    62
    State:
    Snowville,Virgi
    No I did not put anything on it. It has one cap type gasket that slips up over the top part and another gasket that fits down into the lower unit. Both appeared ok. I am attaching a photo of my boat on the trailer. Is it a long shaft or a short shaft? When I look over the back of the boat at speed it appears the water inlet on the lower unit is bearly under the water and the engine skips like the prop might not be low enough. I removed the stingray fin and the boat seem to gain speed but still stoped pumping water. Again it pumps a steady stream with pressure up to about half throttle them it turns to steam and the motor does get hot.
     

    Attached Files:

  10. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Jeffery look at the anticavation plate. The plate that the fin was bolted to and see if it is even with the keel ( very bottom of the boat)

    Look at this picture and it will explain how to measure the lower unit to see if you have a short shaft or long shaft.

    http://img.photobucket.com/albums/v172/coofficer/shaft_length_small.gif


    The way you are describing the problem it seems like the boat is bow heavy and from what I can tell from the pictures it seems to appear that the motor is at the right heigth but you need to take a picture so I can see if the plate is even with the keel or no more then 2 inches above it.
     
  11. jgdishon

    jgdishon New Member

    Messages:
    62
    State:
    Snowville,Virgi
    After two months of pulling my hair out. It was just like Bubbakat and Bob paul said in the begining! There were two teeth stuck up in the engine housing from the oringional impeller that broke. I could not see the area were they were because the water jacket gasket hid it from me. At law RPM the water pressure fromthe pump was not high enough to hold the rubber teeth up against the hole that let the water into the water area around the cyl heads.
     

    Attached Files:

  12. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Alright, pictures too.

    I've had impellors with broken fins, but was always lucky enough to not have them be blocking any water passage.

    Bubba will be pleased you found them also.