40hp evinrude cooling problem

Discussion in 'Bubba's Outboards' started by beagle777, Oct 26, 2009.

  1. beagle777

    beagle777 New Member

    Messages:
    60
    State:
    Il
    I have a 88 40hp evinrude 2 cylinder that the waterpump was getting bad so I put a new impeller in it and it was pumping water very good for a couple hours , then it stared to pump less then none. I did not let it run long enough to over heat but when I put my hand at the telltale hole I could feel exhaust pluses coming out. I'm thinking that it is the head gasket but the motor starts and runs fine, is there any place else that exhaust presser can get into the water jacket. Thanks for any thoughts, tips ,or hints.
     
  2. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    You might check the t-stat. There is one on that motor right? You know the old trick of putting it in a pot of water on the stove? You also might chect the alignment of the water tube and the o ring on top of it. I could be way off. But that is what I would check.
     

  3. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    Since you said it pumped water for a couple of hours I assumed you were running it out on the lake rather than in a test barrel. If it was in a barrel make sure the water level is over the cavitation plate. Those big motors can empty a barrel of water pretty quick. You may even had it hooked up to muffs. I dunno. I am just trying to figure out why it pumped for a while then stopped.
     
  4. tofish

    tofish New Member

    Messages:
    3,923
    State:
    arizona
    you might want to try replacing the whole pump assembly also instead of just impeller. just a thought.
    gary
     
  5. Branj796

    Branj796 Member

    Messages:
    911
    State:
    Illinois
    Well if I was you I would take it and have it looked at by someone who knows what they are doing. The worst thing you can do to a motor is overheat it. It is probably something simple but unless you work on them you will not know what to look for. SOmeone who does work on them will get you straightened out. I wouldn't take any chances. I know from experience.
     
  6. catwhisper

    catwhisper New Member

    Messages:
    456
    State:
    georgia
    get the motor hot and check the compression see if your losing compression when its hot.
     
  7. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    I would say pull the lower and see if the key gave way. If it hasn't check the pick up tube run water up through the pick up tube and see if it comes out.
    Was you feeling this at the exhaust port relief holes or has a pee hole been installed on this engine.
    Last pull the plugs if you have a gasket leaking then the plug will pretty and clean.
     
  8. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    Outboards are similar in some ways to an automotive engine. The cylinder walls need a coating of oil. Most outboards get its oil from the fuel mixture. The cooling system in an enclosed system, and whereas the motor may get warm due to poor compression, it should not get hot. If the motor is heating up, look for the fault to be in the cooling system, which includes the water pump, impeller, pickup tubes, and head passages. Since it overheats after it has ran for a while, you can discount things like a mud dauber blocking the pee hole. I would pull the lower unit again and go over it pretty thoroughly. I'll bet you'll find the impeller is bad (even though you just replaced it) the water pump has grooves worn into it, the woodruff key has sheared or is not in the gear shaft. But believe me, it is in the cooling system somewhere.
     
  9. 7mmmag1

    7mmmag1 New Member

    Messages:
    94
    State:
    Oklahoma
    Before you pull the unit back off I would try hooking up earmuffs to it with a short section of hose. Run the hose into a 5 gallon bucket of water, if it empties the bucket the impeller is fine
     
  10. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    That will not work because the pump is designed to pick up water after it is surmerged in water. It has to be feed into the pump. It can pass enough water through it with a set of muffs with the water on full force that it will give you the impression that the pump is working good.
     
  11. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri

    I was going to tell you to check the driveshaft key, like Bubbakat suggested. Also it is possible that if the old impeller was in was in bad shape a piece of it could become lodged in the water tube. I always worry about pieces breaking off and being lodged God knows where. A friend of mine said he pulled the lower unit, took out the t-stat and put a hose on the water tube to see if things were clear. Might be worth a try since you are probably going to have to pull that lower unit again. Keep us posted.
     
  12. beagle777

    beagle777 New Member

    Messages:
    60
    State:
    Il
    I took the lower unit off and checked and pin was still in, every thing looked good.
    But when I started to reassemble it I was turning impeller to line it up with pin and the rubber part slipped on the inner metal ring.
    Returned it to boat shop and they said it wasn't common but they had seen it before.
    I will get it back in the water this weekend to check it out .
    Thanks for all the help. I have changed the impeller on this motor at least every other year and never had any trouble so I was thinking the worst.
    Hope you never get a bad impeller like I did, but watch that pee stream. If I had been running down the river when it came loose I could have cooked my motor as it was I was putting around in some backwater. Lucky this time.
     
  13. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    Thanks for the update I have heard of that happening on some aftermarket impellers. Good catch.
     
  14. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Thanks for the report back to let us know. Aren't you glad it was an easy fix.
    You buy quantity now days not quality so your percentage of defects are gonna climb.
     
  15. beagle777

    beagle777 New Member

    Messages:
    60
    State:
    Il
    I put the lower unit back on Friday and it was pumping water while the starter was cranking after about three seconds.Motor ran good all weekend.Thanks for all the help.
    I was baffled and was tiring to over complicate the problem. Hope it never happens to you but now you have heard of it and will have something to check a brand new OMC impeller spinning is a new one on me.
     
  16. Tim70

    Tim70 New Member

    Messages:
    48
    State:
    Maplewood, Missouri
    Wow, I am surprised that that happened on an OMC. I remember a few years back when that was happening with the Sierra impellers. There was a bad batch or something. Glad you got her pumping again.