Speedometer Problems...Mercury 90HP

Discussion in 'Boat Repair Help' started by wheat72, Jul 29, 2006.

  1. wheat72

    wheat72 New Member

    Messages:
    2
    State:
    WV
    I have a 1998 Mercury 90HP Outboard that the speedometer just quit working. My Service Manual does not offer any help in solving my problem. The hose that runs to the lower unit looks fine. Where should I troubleshoot to fix the speedometer?

    Thanks!
     
  2. trnsmsn

    trnsmsn New Member

    Messages:
    1,214
    State:
    Missouri Originally Now I
    Disconnect The Hose On Both Ends & Blow Some Compressed Air Thru It, The Water Supply Is Probably Not Reaching The Speedometer Head.

    Have A Great Day & Good Luck, Elliot
     

  3. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    They are bad about getting stopped up where they pick the water up at the lower unit. Just put a little air thru it from both ends. When you do this and hit the water again it will take it a few to pick the water back up again so give it time. A couple min should do it.
     
  4. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    Okay, I need an education. I thought you had the speedometer, line and pitot tube. The pressure of the water against the tube compressed the air in the line which was recorded on the speedometer. So, is it the compression of air or is it water which causes the meter to read?
     
  5. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    lawarence to tell you the truth I will have to research that one. Now you got me corn----fused:big_smile:


    Where is the aspern I have a head ache.:lol:
     
  6. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    It is compressed air by means of water pressure.

    Thos Mercs, like many newer engines have the pitot tube pick up built into the lower unit.

    Right in front and near the bottom of the lower unit, is a hole that gets plugged up. If you see a hose coupling between the lower unit and mid-section, seporate it there and blow compressed air in towards the lower unit.

    That should unclog it

    Do not blow air towards the speedometer.
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Bob I am glad you intervened here. I was about to have a nervous break down because Lawrence ask a question that I didn't have an answer to.:lol:
     
  8. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Any time Bubba. Got yer back.

    I get a feeling Lawrence was asking a question he already knew the answer too. That can be a bit unnerving.

    Next time he does that, just say," Hey, who gives a s--t". It'll do wonders for your nerves.:lol:
     
  9. duxsrus

    duxsrus New Member

    Messages:
    1,014
    State:
    SW Ohio
    Every Merc I've ever owned has had the pickup hole get stopped up several times. I keep the correct size drill bit in the boat with me so if I notice the gauge is not working, I just drill the hole out by spinning the bit with my fingers gently. It just takes a second to clean the hole out.
     
  10. wheat72

    wheat72 New Member

    Messages:
    2
    State:
    WV
    I Tried Compressed Air And No Luck. In The Lower Unit Where The Speedometer Pickup Is...could There Be Something In There That Might Be Causing Me Troubles? If So, How Big Of A Job Is It To Get Into The Lower Unit And Fix It?

    Thanks For All Of The Help!!!!
    Barry

    Ps: I Was In "real Shallow Water" Right Before It Quit Working.
     
  11. Bobpaul

    Bobpaul New Member

    Messages:
    3,039
    State:
    Supply NC
    Have you tried the tiny drill bit in the hole first then compressed air?

    dropping the lower unit is no big task, just remove all the bolts and you might have one under the trim tab and it'll come down. drive shaft and shift shaft are spline fittings, Just be sure they mesh well during replacement.

    You might want smoeone else with you to disconnect the plastic speedometer tube when you lower the lower unit.