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Results 1 to 8 of 8
  1. #1

    Default Constant Alarm on 2004 Mercury 150 hp Saltwater series - help

    I have a 2004 150 saltwater series mercury outboard. I am having a problem which seems to be common by reading a LOT of posts. I have a bay boat that I take off shore a lot. If conditions are rough, I take it easy going out. If I try to keep my speed at around 20 mph, I have a constant alarm that goes off. Water pumps appears to be working as motor pees just fine. If I shut the motor down and wait for about a minute and a half, alarm is gone when I start it back up. Alarm comes back on within a quarter of a mile. The alarm doesn not sound when I idle or run wide open. Any thoughts?

  2. #2
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,197

    Default Re: Constant Alarm on 2004 Mercury 150 Saltwater series - help

    You will need to check the temperature of the cylinder heads when this alarm goes off. If you can lay your hands on them for say 5-10 seconds with out it being uncomfortably hot then the engine is not over heating. The temp sensor may be defective. The best way to check it is to get an infrared temp gun and read the actual temp of the cylinder heads. They should be around 120-130 degrees F.

    If the temp is higher it's time to check the water pump, (physically check the water pump), the t-stats and the bypass valve.

  3. #3

    Default Re: Constant Alarm on 2004 Mercury 150 Saltwater series - help

    Thank you. It may be time to replace the water pump anyway. I just couldn't understand why the alarm for only the situation I described. Thanks again.

  4. #4
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,197

    Default Re: Constant Alarm on 2004 Mercury 150 Saltwater series - help

    The hub in the center of the pump impeller could be slipping or the pump can cavitate and cause an over heat at higher RPM's. After market pumps are not the same quality as Mercury pumps. The slipping impeller hub is a common problem with cheaper aftermarket parts.

  5. #5

    Default Re: Constant Alarm on 2004 Mercury 150 Saltwater series - help

    One more question. I've seen the water pump changed online however, there weren't any instructions about the wiring harness. What steps are there for disconnecting and reconnecting?

  6. #6
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,197

    Default Re: Constant Alarm on 2004 Mercury 150 hp Saltwater series - help

    Why would you need to disconnect the wiring harness to do a water pump?

  7. #7

    Default Re: Constant Alarm on 2004 Mercury 150 hp Saltwater series - help

    I wouldn't. I just saw something on a video and didn't know what I was talking about. I actually removed the lower unit last night and changed the water pump. After tightening the housing down, I'm wondering how freely the spindle should turn. For instance, should you be able to turn it with your fingers or should you have to use your hand to turn it when trying to line up the teeth to seat it? I just want to be sure that I didn't tighten the housing down too tight. I'm also having trouble getting the lower unit back in. I'm wondering if the tube that runs parralell with the spindle is not sliding into place. Any advice on these two questions? By the way, I really do appreciate your help and suggestions. This is the first time I've attempted any type of maintainance on my motor so please forgive my lack of knowledge.

  8. #8
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    3,197

    Default Re: Constant Alarm on 2004 Mercury 150 hp Saltwater series - help

    You should have to use your hand to turn the drive shaft. You will need to turn the flywheel on top of the engine while trying to install the lower unit. Once that is lined up concentrate on the shift rod.

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