Yamaha 90 2 Stroke Water Pressure

Discussion in 'Outboard Maintenance' started by rkmurphy, Aug 11, 2012.

  1. rkmurphy

    rkmurphy Well-Known Member

    Hey all. I have a 2001 Yami 90 2 stroke that has been an absolute beast. Love this motor!

    I had my water pump done professionally a couple years back and, recently, the water pressure started to dwindle eventually making its way to sub 10 psi. So, I went ahead and bought a rebuild kit and just did it myself (that dad gom impeller key is impossible to get out, btw! :mad: ). I also tested the thermostat in some boiling water and it opened up just fine. Replaced the gasket and popped it back in.

    Anyhow, I took the boat out last weekend and the water pressure still is around 10 psi. The overhead alarm isn't going off or anything, but I've had higher pressure before. Any thoughts?
  2. Brett

    Brett > PRO STAFF <

    Hey RK, been awhile. Sounds like you just replaced the soft components
    not the housing or base plate. Might be a small loss of pressure there
    due to loose fit. Also could be corrosion buildup, or debris in the passage ways
    through the block leading to the tee that feeds the gauge. Or, maybe
    a poppet valve that has stuck or worn so that less pressure is needed
    before the poppet activates.

  3. rkmurphy

    rkmurphy Well-Known Member

    The only hard component that was replace was the metal insert within the casing. I cleaned up all of the gasket mating surfaces and the base plate really well...so I don't think that's it. Where would this tee be that you speak of? That might be my next place to check. Also, where would I find the poppet valve? I could check that, too.

    Good to hear from you again, Brett. It sure has been a while. I'm relapsing my fishing addiction...hopefully this time I never recover!
  4. Brett

    Brett > PRO STAFF <

    Yamaha doesn't call it a poppet valve,
    their nomenclature makes it a pressure control valve, part # 40


    The associated grommets that go with it wear out too.
  5. DuckNut

    DuckNut Brandon, FL

    Is the stream weak or just the gauge?

    Welcome back Murphy.
  6. rkmurphy

    rkmurphy Well-Known Member

    Hey there! The stream seems a little weaker than it should be. I mean...it still pees...but after I took it to Alafia Marine when I had it done professionally, it was like Mr. Ed.

    Brett, I did look at that diagram after I read your initial response...love that site! Good prices on parts, too. Is there anything specific I should be looking for with that valve or the spring? I noticed it when I checked the thermostat and it wasn't stuck or anything. I cleaned out the hole and all of the areas with a dremel and very light wire brush.

    Thanks for helping me with this guys...hopefully it's just something stupid that I can easily take care of without spending a bunch of money!
  7. DuckNut

    DuckNut Brandon, FL

    Had a similar issue years ago. At the top of the intake tube there is a rubber grommet where it attaches to the head. Corrosion gets benind this and grows until it squeezes it closed.

    This was found by tearing the motor apart and then cleaning. I now fill a bucket with water and put the lower unit in it and mix in some CLR and run it for a while. Then I do it again with salt away and has been trouble free for 10 years.

    I looked n the pictures that Brett linked but can't seem to find the intake tube.
  8. rkmurphy

    rkmurphy Well-Known Member

    I love the CLR idea. Brilliant! I'll have to try that. Maybe even today! About what ratio to water did you mix the CLR in? Will this affect my seals or gaskets? And is the Salt Away completely necessary? If so, where can I find it?

    I'm looking for a way to avoid tearing the motor apart...been there done that with my old Merc.
  9. twitch

    twitch Well-Known Member

    Where is the water pressure gauge getting its feed from?

    Is it T 'eed into the the pisser tube or is it fed through the water jacket?
  10. Brett

    Brett > PRO STAFF <

    DN, the intake tube is part of one of the lower unit parts lists
    along with the water pump and gearbox diagrams.

    RK, anytime a spring or neoprene seal is involved, time and salt/corrosion deposits
    cause the springs to weaken and seals to split or distort allowing pressure leaks.
  11. DuckNut

    DuckNut Brandon, FL

    I just bought one of the roughly 10-12 gallon buckets from Lowes - the ones a keg fits in - put the lower unit in fill it up and dump the jug of CLR in.

    Hook a hose up to the pee tube and put it back in the bucket. Keep in mind the water will get hot when it is idling. Don't let it get too hot.

    I use one jug of CLR then again with same amount of Salt Away. I can not say if the Salt Away does anything more than doing it again with clean water to ensure it is rinsed.

    After this episode cost me several hundred I have been doing it at least twice a year depending how much it is in salt water and 10 years later all gaskets and seal still working. Just make sure you do it once with clean water to make sure it is rinsed.
  12. rkmurphy

    rkmurphy Well-Known Member

    Okay so here's what I did...

    My Yami has one of those silent flushing attachments that lets you flush it without the motor running. So, I poured some CLR in the faucet end of the hose, turned it on for a few seconds, and let it sit for a few minutes. Then I put some dish soap in the faucet end of the hose and followed the same procedure. I did this twice then did the silent flush with straight fresh water for about 20 minutes, then backflushed through the pee tube. I'll let you know if this has any effect tomorrow. If it doesn't do much, I'll give your method a shot.

    As far as the pressure tube, it connects to the head. No tee joint or anything that I can see. Either way, the stream is what seems a bit weaker, not just the pressure read.

    Brett, the PCV seemed fine when I checked the thermostat. It's definitely not worn or weak.

    Gotta love this stuff!
  13. Snookdaddy

    Snookdaddy Well-Known Member

    I'm 100% sold on the "silent flush" method or any flush method that doesn't require the engine to be running.

    Here's my question: How does the thermostat fully open if you're running room temp water out of a hose into the outboard?

    It is my understanding that the cylinder head doesn't get much water until the the temperature rises enough to open the thermostat.. How will this system flush major salt deposits in the cooling passages surrounding the cylinders if the thermostat does not open?

    I'm not a marine mechanic, but I'd really like to know if the outboard gets completely flushed without the motor running.
  14. cutrunner

    cutrunner Cert. Yamaha technician

    Your answer,
    It doesent

    You are correct, for a complete flush it needs to run onthe hose to get to full operating temp to openthe thermostat.

    Rc: right before you replaced the waterpump was it pumping stonger than it is now, after you replaced it?

    Did you use a Yamaha impeller or aftermarket?

    We'll start there
  15. rkmurphy

    rkmurphy Well-Known Member

    #1 I ALWAYS run on the hose AND silent flush. If I only do one, I run on the hose to flush it.

    I took the boat out Monday morning and the stream looks solid coming out of the pee hole. Now I'm starting to think it might just be the gauge...

    I'm going to attempt the CLR in the bucket thing at some point over the next month or so and see what happens, too.

    Keep the suggestions coming guys. You are a huge help, as always! :)
  16. JimL

    JimL I Love microskiff.com!

    Mine had the exact same issue. Replaced the water pump, poppet, spring, thermo and the alarm still screamed at 4500 rpm and shut her down. CLR or whatever is a waste of time and money. You need to get a yamaha guy to clean the water jackets in the engine. CLR will never remove the deposits that have built up over the years. This is a very common problem with the 90hp Yami.. I spent $275 to have mine done and he replaced the thermo to boot.. Ran perfect at all rpm's after that.. Pay now, or pay again later..
  17. rkmurphy

    rkmurphy Well-Known Member

    I'll have to price that out. Water pressure seems fine especially at higher RPMs. And alarm doesn't come on. If it does, it's usually because a bunch of grass kicked up on my LU and blocked the intake. Either way, I'd rather make sure it's tip top shape. May be something to use some Christmas money on. Until then, it's running, running great (for now), and gets me to my favorite spots. Hopefully no issues for a while! I'll keep you all posted. Keep your thoughts and experiences coming! Thanks guys!
  18. rkmurphy

    rkmurphy Well-Known Member

    So I went and got a price only to be told by one place that they had done similar jobs before and the labor costs would probably not be worth it. Another place (my main source for trusted motor work) priced me at about $350-$400. He said he is willing to take care of it but suggested I try something else first. The name of the product is Hammerhead Marine Descaler by Bright Bay Products. It's a biodegradable product that is safe for aluminum and attacks calcium and rust in outboard and inboard motors. Apparently it was originally developed for AC systems. They sell commercial systems to outboard repair shops and there are a couple in my area who were asking $250 for the service.

    So, since I could get it manually cleaned out for $350 or so, I decided I would take matters into my own hands. I built my own little system with a submersible pump from harbor freight and the Descaler product is only $40. So for around $70 total, I figure I don't have a ton to lose. I'm waiting to receive the product in the mail and will keep you all posted with the progress. Hopefully this works and is a good option for some of you on this forum who may run into a similar problem or just want to prevent such a problem. I've seen a video of this stuff dissolving shells so I think it may at least help a bit. I've also heard some 3rd party testimonials that this stuff is legit and made a night and day difference.
  19. cutrunner

    cutrunner Cert. Yamaha technician

    If i may, i would like to kinda "slow your roll".
    I believe i may know what your problem is, hopefully.
    Every 90 2 stroke i have ever ran (thousands..) when hooked up to the silent flush, with the hose turned on(motor not running), peed, just as hard as when it was running.
    If i remember correctly you say you are getting good water pressure on the guage, and you arent throwing any alarm buzzers?

    Have you tried disconnecting the pee hose from the little plastic nipple in the pan and pulling the other end off as well that connects to the barb on the exhaust cover?

    You could very well just have a tiny shell or mud dobber halfway clogging up the hose or plastic pee hole nipple insert in the pan. It happens ALL the time.
    If you havent tried that yet, please do!
    Remember, if your motor truly isnt overheating and your buzzer is properly working, your not overheating. Its only a tell tale so dont let it snowball into something bigger.
    Let me know if that works for you
  20. rkmurphy

    rkmurphy Well-Known Member

    Haha yes sir this is the first thing I checked, honestly. I disconnected it and ran some 80lb test through it to clear anything out that may be in there. I wanted to get rid of the simple solutions before moving forward with anything. Thanks for looking out, though :)