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Thread: 2004 Yamaha 90 2 Stroke?

  1. #21
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    I ordered the H2O pump and T-stat. I never did change the T-stat, thinking that may be the culprit but I’m changing them all and going get the jackets cleaned too.
    Yeah, but do you consider a dog to be a filthy animal? I wouldn't go so far as to call a dog filthy but they're definitely dirty. But, a dog's got personality. Personality goes a long way.


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  2. #22
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    Mar 2016
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    Horry, SC
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    My 2003 90 Yamaha did the same thing. Mine was the impeller, took maybe 30 minutes to change.

  3. #23
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    Mar 2002
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    The rubber impellers sit in an eccentric housing so half of the blades get a bend set in them if they sit a while. If you don't lolligag at the landing at idle and go ahead and put the throttle in the corner, the water intake ports will usually force enough water in the keep the engine cool while the impeller blades limber up. Keep your eye on the pressure gauge and/or pisser for a while but it will usually heal itself, until the next time you let it sit for a while.

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  4. #24
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    Feb 2004
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    Quote Originally Posted by Saltydog235 View Post
    Yeah, I've replaced it before. Would the impeller dry rot without being used? Seems like it is in a sealed area and that wouldn't be likely but I'm no outboard mechanic.
    I have seen stranger things...
    Honey...I'll do it after the season is over.


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  5. #25
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    Dec 2010
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    pull thermostats out and look at them, easy enough
    put them in a pot of boiling water and see if they open up and
    then take a pair of tongs and remove from boiling water and you should
    see them close as they cool off

    Its most likely not your poppit valve if it does it at idle and not higher rpms.
    When you run at idle, you are running on the thermostats, when you throttle up and run at high speed, the poppit takes over.
    The poppet opens up with the higher water pressure (its just a plunger on a spring) brought on by higher rpms and dumps the excess water that the water passages
    can't handle. Poppit valve symptom is usually only over heating at higher rpms and not over heating at idle

  6. #26
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    Sep 2019
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    Florida/SC
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    If you don’t want to pay for a new impeller it is simple to drop the 3 bolts on each side and do a visual inspection. That being said lack of use is the death of boat parts. My rule of thumb is impeller every year for my flats boat and every 2 for offshore depending on use. I still drop low units yearly though to avoid seizing. Oil changes every 100 which you don’t have to worry about.
    Another tip if you do pull sand or a little debris is I have use my kids water ballon filler and attached on exit hose to “reverse flush”. More often than not it dislodges the material so when I put back on muffs it flushes.

  7. #27
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    To clean the innards, I bought a Harbor Freight pond pump and used Tygon tubing to run a 50/50 solution of vinegar through it for 6 or so hours. The pump fed from a bucket the collected the flush frontage motor. It was amazing how much sediment the bucket had when it was done.
    Honey...I'll do it after the season is over.


    Originally Posted by cudexter
    I would argue that JP has the highest "quality" to "trash talk" post ratio on this site.

    Quote:
    Originally Posted by Air Raid
    ... Wait till 3 years from now! ...



  8. #28
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    Nov 2002
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    FloVegas SC
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    Those 3 cylinder 90's are easy for many reasons but one is getting to the water jacket. What everyone has said is mostly accurate and helpful and all of them require low $ and low skills to perform. My $.02 is that you have some sand in your passageway. I have never heard of the sump pump flush like JP detailed. It sounds effective. Taking that cover off of the water jacket on the side is easy and outside of the new impeller and t stat, is not a bad idea. Those passageways are smaller than you think. Also, most guys on the coast replace the pee hole with a much larger diameter hose so sediment does not clog it up. OR just pm me and I will take it off your hands, all of the 3 cylinder Yamahas are gold. MG
    Dum Spiro Spero

  9. #29
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    Nov 2005
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    Fort Kickass
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    Quote Originally Posted by Maggie Glover View Post
    Those passageways are smaller than you think. Also, most guys on the coast replace the pee hole with a much larger diameter hose so sediment does not clog it up.
    Be advised...

    I did this. Bored out the little outlet that would allow more water to flow, too.

    The logic is there, but those things operate on water pressure and if you do this, you will over heat the top cylinder and burn it up. Ask me how I know...Took two burnt cylinders over the span of two years and a trip to a good mechanic to tell me this.
    Last edited by BigBrother; 06-30-2021 at 07:54 AM.
    "Rivers and the inhabitants of the watery elements are for wise men to contemplate and for fools to pass by without consideration" -Izaak Walton

  10. #30
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    Mar 2002
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    Good to know BB.

    I removed the outlet and just ran the line thru the lower cowling. I’ve been running it like that for several years but might rethink that now.


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  11. #31
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    Nov 2008
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    Scumter
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    The pee hole is indeed just a visual indicator. Trying to make more water flow thru it is an exercise in futility. The bulk of the water is really circulating thru the head then coming out of multiple holes in the lower unit. Just leave it be.

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