Water pump theory question

Home Forum Ask A Member Water pump theory question

Viewing 10 posts - 1 through 10 (of 26 total)

  • wetwillie


    Replies: 91
    Topics: 15
    #5030

    I hooked a garden hose up to my ’79 Evinrude 35, turned on the water and started the motor for the 1st time since I bought it. No water flowed out of the indicator tube after 30 seconds of running so I shut off the engine and figured the impeller was shot.
    I was surprised to find the impeller in such excellent condition. NO obvious wear or cracking on the vanes and very flexible. I figured there must be an obstruction so I blew air into every passageway. Not a single blockage.
    I put the impeller back in the housing and reinstalled the lower unit. My thinking being that surely it’ll work this time. It didn’t. Water flows out of the exhaust but nothing comes out of the indicator. When I pulled the indicator line off the motor, I felt hot air coming out of the fitting but not a drop of water. I shut the motor off and began to wonder what was going on.
    Out of curiosity, I squeezed water into the fitting that connects to the indicator outlet and water came out the exhaust, not the intake for the pump.
    Although I have every intention of replacing the impeller before starting the motor again, I would like to know why water will flow out the exhaust w/o a problem but not make it to the indicator outlet.
    Thanks,
    Wet Willie


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #42420

    Well, there is some bleed off the pressure side of the pump before the water gets up to the powerhead, probably a bleed hole in the water tube as well, which explains the water coming out of the exhaust. I know you say you felt hot air coming from the overboard indicator, but are you sure that passage is clear. It is very common for the elbow to get plugged, and for stuff to get jammed in the plastic outlet that snaps into the motor pan. Have you removed the outlet nipple? I would remove it and blow back through the hose with compressed air.
    The location of the cooling inlets is all the way near the leading edge of the gearcase, not the best design. It is very tough to get ear muffs to seal around them very effectively. You might want to put the boat in the water, or sink the engine deep into a test tank/barrel before going too far here. In other words, you may not really have a problem at all, hopefully anyway…


    wetwillie


    Replies: 91
    Topics: 15
    #42424

    Thanks Fleetwin. I believe the elbow is clear because I blew through it and also the hot air coming out. As for the possibility of there being a bleed hole in the water tube, there isn’t. I checked. That’s another reason I wondered just where is the water coming out the exhaust coming from.
    I agree with the water muffs not making a good seal. I noticed that and addressed that issue the 2nd time I ran it by duct taping the muffs tight to lower unit. 🙂
    I’ll be ordering a new impeller on Monday. My only delay is wanting to order one for a ’59 Super Seahorse that I’m taking delivery of on Monday. I figure I can save a little on postage if I order 2 at the same time.
    Finally, speaking of ordering parts (ie. water pumps and possible carb kits)…I’d appreciate all recommendations for the least expensive online source? 😉


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #42425

    So, you pulled the water tube out of the exhaust housing? Perhaps it is misaligned, kinked, not seating properly in the grommets. Does the engine show signs of overheating, burnt paint, melted harness? I’m assuming you just got this engine and have not run it much.
    Anything is possible, I suppose the inner exhaust tube could be cracked/corroded away where the inlet water passes through. You could test your theory by removing the gearcase, then rigging up some sort of hose/reducer to the inlet water tube. Now tilt the engine up and turn the water on gently, look up inside with a flashlight for big inlet leaks/problems.
    Sometimes the upper water tube grommets on this engine family gets crushed/deformed causing a water restriction, or perhaps a leak. Maybe you can see up inside with the tube out. Is this a salt water motor? This problem is not as common on fresh water engines. Sure hope I am wrong about this, don’t want you to have to pull the powerhead.


    wetwillie


    Replies: 91
    Topics: 15
    #42429

    I pulled the water tube out of the exhaust housing when I removed the lower unit. I’m confident that it the tube was correctly inserted into the grommet when I removed it based upon the end of the tube being shiny. There are no obvious signs of the motor having overheated.
    You are correct about my having recently purchased the motor. This was the 1st time I’ve started it.
    Tomorrow, if possible, I am going to attach the garden hose to the water tube (the lower unit is currently off while I wait for the pump I ordered this evening to arrive) and turn on the faucet. I will see if the water will make its way out the overboard indicator. I’ll know there’s no blockages if it does.
    I’ll report back after I’ve completed this test.
    I appreciate your input.


    frankr

    US Member - 1 Year (includes $3 online payment fee)
    Replies: 6715
    Topics: 51
    #42431

    Sure sounds like there is a problem in the area of the upper water tube grommet #115 allowing water to just spill out into the exhaust instead of going through the powerhead. But that’s just a fairly reasonable guess.

    free image host


    collectorinspector


    Replies: 145
    Topics: 21
    #42432

    Pull the thermostat out and run it.

    With it out what happens?

    I mean run it in a barrel with the thermostat removed.

    Nothing else……just in a barrel.

    The cooling is very basic for these by the way. There can not be very many problems that you can not sort.

    Interested though…….any pics would help aye!

    BnC


    billw

    US Member - 2 Years
    Replies: 2071
    Topics: 66
    #42433

    As Fleetwin said, the ’79 has the water pick up forward on the gear case. It is kind of hard to get ear muff flushers to seal tightly on them. I, too, would put forward the simple idea that maybe you just don’t have enough water flowing to the flusher from the garden hose. Sometimes I tie the muffs on so they won’t lift and move around on the gear case and open the garden hose supply quite wide.

    Outboard cooling systems are designed to drain out when you shut the motor off. It is sometimes possible to supply so little water that the power head drains as fast as it fills. The result is exhaust in the cooling system and sometimes, it will come out the tell tale hole.

    As for running this motor without the thermostat, it is under a whole water jacket cover and would be a pretty big operation to just take it out, for a test. Is there any way you can test the motor by backing it into an actual lake on a trailer, to eliminate the ear muff flusher as a problem?

    Long live American manufacturing!


    wetwillie


    Replies: 91
    Topics: 15
    #42442
    quote BillW:

    As for running this motor without the thermostat, it is under a whole water jacket cover and would be a pretty big operation to just take it out, for a test. Is there any way you can test the motor by backing it into an actual lake on a trailer, to eliminate the ear muff flusher as a problem?

    Thanks for answering the question that came to mind re: removing the thermostat. I felt I had the poor sealing of the water muffs solved when I duct taped them on. I don’t have access to a large barrel I can run it in but may be able to back in to a local lake. I’ll try that after I connect the garden hose to the water tube and see if water comes out the overboard indicator. However, wouldn’t a closed thermostat prevent that from happening?


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #42443

    There is a small bleed in the thermostat that allows some water to sneak by, even when closed. Keep in mind that the overboard indicator is before the thermostat in the cooling flow, so a completely salted up plugged/stuck closed thermostat would still show good flow from the overboard indicator even though the engine would surely overheat.

Viewing 10 posts - 1 through 10 (of 26 total)
  • You must be logged in to reply to this topic.