How do you know when you need a new impeller?

Discussion in 'Outboard Maintenance' started by bamboobill, May 18, 2011.

  1. bamboobill

    bamboobill I Love!

    So I was having trouble getting my Nissan to run.  I had it on the muff and was cranking it and checking stuff, but I kept getting called away by the wife and kids.  When I'd leave the boat I'd shut off the water.  You can see this coming, can't ya?  I returned to the boat at one point and proceeded to crank the motor 3 or 4 times WITH THE WATER OFF before I realized it (idiot).  I'm talking long 6 second spells of leaning on the starter. 

    The motor is now running great after draining the tank and adding fresh gas and a better stabilizer (old, bad gas - Sta-Bil marine didn't cut it).  But now I'm paranoid about the impeller.  It pees good with a little RPM on it and strong opened up, but seems a little weaker than I remember at idle but that may just be my imagination.  Also, at idle I see what sorta looks like micro bubbles in the stream for a split second every now and then.  The stream is steady - I'm just seeing these flashes of more opaque water.  I don't recall seeing that before but can't say I really looked that closely either.

    So am I okay for now or do I need to consider replacing the impeller?
  2. Brett

    Brett > PRO STAFF <

    Install a water pressure gauge.
    Inexpensive way to keep an eye on through block water flow.
    If you're really worried about it, how long has it been since you changed the impeller?

  3. bamboobill

    bamboobill I Love!

    It's a 2010 with 20 hours on it, so it's still the factory impeller.
  4. Brett

    Brett > PRO STAFF <

    My guess is you're still good. I'd still install a water pressure gauge.
    It's a better device for monitoring the cooling system than the temperature gauge.

    previous discussions of the water pressure gauge...,or.r_gc.r_pw.&fp=c4b94ef403c105f7
  5. Swamp

    Swamp I Love!

    6 sec intervals at starter motor RPMs shouldn't do much, especially with a "still new" impeller. However there is something to be said about cracking the lower unit off on a regular (every year or two) to keep it from seizing. Been there done that. :-[ I agree with the water pressure gauge comments.

    Personally I would not worry about it especially since there was still likely to be some moisture in it. But if it's going to bug you get a new impeller.

  6. mark_gardner

    mark_gardner I Love!

    i have run my motor easily that long without water and have way more hours than you and the impeller pee's like a race horse :D ;D i wouldnt be so concerned about it peeing the way you said it does on the muffs, they sometimes are hard to seal and suck air causing what you describe as micro bubbles, take it down to the lake and fully submerge the lowerunit and see what happens, the pressure gauge certainly is a good idea :cool:
  7. makin moves

    makin moves Well-Known Member

    If it helps my tohatsu out of the box never really pee'd hard at idle. As soon as you give a little gas different story. I asked the tohatsu mechanic about it because every motor I have had in the past would always push more water than this motor his reply was it was the norm for that motor.
  8. Gramps

    Gramps Living &amp; Dying in 3/4 Time

    What MM said. The TLDI motors are a high volume low pressure setup. Basically if you throw a gauge on a brand new impeller at WOT it will only read about 7-8lbs which is about half the pressure of most other motors in the same class.

    Ask Mel about getting a factory gauge, they have the correct calibration but geez-o-mitey they're expensive.
  9. noeettica

    noeettica Well-Known Member

    Just Install a New Impeller ..Peace of mind ;)
  10. Brett

    Brett > PRO STAFF <

    Sounds like another Jeff Foxworthy routine...

    If your outboard starts to whistle like a tea might need a new impeller.

    If you can froth your latte with the steam from your whizzer might need a new impeller.

    If you can poach a shrimp by holding it under your whizzer might need a new impeller.

    If you can soften an old gulp watermelon shad by dangling it in the spray from the whizzer might need a new impeller.

    If you can remove gum from the bottom of your shoe by holding it under the whizzer might need a new impeller.

    If you can brew expresso with the output of the whizzer might need a new impeller.

    If bits of neoprene are floating up along with your exhaust might need a new impeller.

    If your whizzer pressure is better with the flush muffs might need a new impeller.

    If you accidently let your fishing line intersect the spray, and it might need a new impeller.

    If you can whiz further than the outboard whizzer tube, without first downing a six might need a new impeller.

    If the engine cowling starts to char, like the crate in Raiders of the Lost might need a new impeller.
  11. topnative2

    topnative2 Well-Known Member

    prostate trouble uasually............shoot wrong site ;D
  12. Swamp

    Swamp I Love!

    So do you crank the motor to one side and tilt it up all the way when checking? Don't forget to warm up your hands and wear a rubber glove, that gear case oil stinks for a week! :eek:

    I'll stop now. ;)

  13. topnative2

    topnative2 Well-Known Member

    the words of experience........... ;D saves us novices'again :p
  14. Frank_Sebastian

    Frank_Sebastian Well-Known Member

    The flushing attachment and house water pressure make it hard to tell anything about the impeller. Check it while it is in the river and warmed up so the Tstat is open.

    Your impeller was not likely damaged by any 6 second run and especially if it was already wet.

    Best regards,
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