OK - I'm stumped - Honda 20 water pump

MistermtdMistermtd Steinhatchee Posts: 76 Greenhorn
I have a new-ish honda 20 with < 10 hours. It ate a water pump impeller at about 5 hours when I bumped into an oyster bar on a dead slow idle. I figured it must have sucked up just enough debris to destroy the impeller but its a pretty fine screen so I was never really sure about that. No biggie - I called the man and had him install a new one. It tested fine on the hose and I thought my problem was solved.

The motor ate its second impeller at 10 hours which I found pretty suspicious. It worked fine the last time I had used it and I had put it on the hose to make sure it would start when I went out the next day.

So, I ordered a whole new kit and did a little research on how to change it. I dropped the foot, took off the old pump, and found what I expected, a second shredded impeller. I removed the intake screen from the lower part of the foot, cleaned out all the bits of rubber, cleaned the pump intake, blew air back thru the pee hole and installed a new gasket, plate, impeller, pump body and o-ring.

I reconnected it to the hose, making sure I had a good seal and restarted it. The pump worked fine for about 30 seconds and then I noticed a significant decrease in output from the pee hole. I immediately shut it down, disassembled the whole thing and inspected it (it was fine), blew the pee hole clear again (no visible debris came out) and reassembled. It continued to operate at a very low flow.

I shut it down and put the foot in a trash can filled with water and tried it a third time. Still very little flow, even at higher rpms. It did NOT over heat though and I would have expected it to do so given the time/rpms I ran it at.

So - to summarize, I've cleared the intake & body of all visible debris. I've cleaned the surface of the pump intake body, installed a new gasket, plate, impeller, key-way, pump body, and o-ring. I've checked the pee hole for obstructions and don't observe any. I've submerged the foot in water well above the pump itself and I still don't get good flow.

What am I missing here???

thanks

Replies

  • surfmansurfman WC FLPosts: 5,080 Admiral
    Is the impeller twisted the right way? When installing the impeller you need to twist it to get it to go into the housing, if you twist it the wrong way it could affect the flow. I have never seen an impeller shred, that's a new one on me.
    Tight Lines, Steve
    My posts are my opinion only.
  • MistermtdMistermtd Steinhatchee Posts: 76 Greenhorn
    Yes - I biased it to drag rather than push the arms which seemed the right thing to do. Its a little odd to figure out since it faces up when you put it in the pump housing and down when you install it. I've been thinking about the hose that connects the outflow of the pump to the engine water jacket. If that had a significant leak it would explain a new water pump not delivering much water.

    When I first installed the pump it worked fine and then tapered off significantly. I installed it with a good coat of marine grease which might have sealed a bad fit for a few moments. That would explain what I saw - good flow for a short moment. I'm going to check it out when I get back to it this weekend.
  • Alex from GAAlex from GA Posts: 1,261 Officer
    Put the impeller on the shaft and turn the flywheel, clockwise, while pushing the impeller down to get the blades the right way. You probably did it that way.
  • flashback62flashback62 Posts: 40 Greenhorn
    You may want to check your thermostat,may be plugged with impeller parts,had a similar problem with 40 hp yami
  • CL604CL604 Posts: 69 Deckhand
    In addition to checking thermostat for debris, many manufactures have water pressure
    relief valves usually located on the side of the engine.If you have one ,its easy to clean
  • MistermtdMistermtd Steinhatchee Posts: 76 Greenhorn
    Ok those are good ideas. I will check them out and report back.

    Thx
  • jawzjawz Posts: 137 Officer
    surfman wrote: »
    Is the impeller twisted the right way? When installing the impeller you need to twist it to get it to go into the housing, if you twist it the wrong way it could affect the flow. I have never seen an impeller shred, that's a new one on me.


    that will never happen...impeller blades will flip to correct themselves....

    that's an old wive's tale....
  • surfmansurfman WC FLPosts: 5,080 Admiral
    You may be right, I never tried putting them in the wrong way to test it but, in the instructions it says to do it that way.
    Tight Lines, Steve
    My posts are my opinion only.
  • jawzjawz Posts: 137 Officer
    surfman wrote: »
    You may be right, I never tried putting them in the wrong way to test it but, in the instructions it says to do it that way.

    you haven't replaced many outboard water pumps have you ?? "wrong way" ??? could you explain that to me ??

    impellers for outboard water pumps are,for the most part - cut,read that as cut to fit the key way in one direction only - there's a up side and down side rotation of blades has absolutely nothing to do with it.the impeller will only go down in place one way...
  • surfmansurfman WC FLPosts: 5,080 Admiral
    I have replaced a few, if you say so...
    Tight Lines, Steve
    My posts are my opinion only.
  • surfmansurfman WC FLPosts: 5,080 Admiral
    Is this a good installation?

    waterpump_zps00e8f406.jpg

    It may still pump just fine though, not sure since again, I have never tried to do this on my motors.
    Tight Lines, Steve
    My posts are my opinion only.
  • Alex from GAAlex from GA Posts: 1,261 Officer
    If the flywheel turns clockwise the pump installation is wrong.
  • Alex from GAAlex from GA Posts: 1,261 Officer
    After looking at it again, I'm wrong.
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