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Thread: Impeller project

  1. #1
    Water Romper
    I am thinking of replacing/servicing my impeller on my 150 Black Max.
    I was told an experienced mechanic can knock this out in a couple hoursÂ…
    Am I getting in over my head? I have the Mercury manuals and have done work on automotive engines however I know outboards are a beast of their ownÂ…
    Any advice would be welcomed!

  2. #2
    Tom Brown
    Am I getting in over my head? I have the Mercury manuals and have done work on automotive engines however I know outboards are a beast of their ownÂ…
    BlackMax impellers are easy, IMO.
    I don't know about an experienced mechanic taking a couple of hours. I can do it in 30~45 minutes.
    The important thing to remember is never twist the shaft the opposite way of the engine because you'll fold the impeller blades backward. Apparently this can be a problem although I've never had cause to test turn it the other way to see what damage would happen to the rubber.
    It sounds like a job you will have little trouble with. The difficult part is getting the damn gear case back on the mid section. It can be a real pain. I've spent 30 minutes trying to get one on. Put the boat in neutral and don't move the stick or twist the shift shaft when the gear case is off and you'll be fine. The shift linkage connects first, then the drive shaft. If the drive shaft baulks, you may have to get someone to twist the flywheel a few degrees to get the splines to line up while you push the LU into place.
    Once you've done it once, it will be no big deal.
    Oh yeah... don't forget the front stud is a little bigger than the rest and will take a different nut. Keep the little tabbed washer and nut from the front stud seperate. The rear bolt is under the turn fin so you have to remove the turn fin (or cover plate if you've deleted the turn fin) to get at it.
    One last thing... it has been recommended to me to always replace the entire housing with a housing kit. The kit comes with impeller, housing, gaskets, etc. I've replaced just the impeller before and it was fine but it's only about 10 bucks more for the whole kit.
    - Tom

  3. #3
    Tunnel Vision
    It's a very simple task, and in my opinion the first time you do it, maybe a couple of hours but the next time, 1 hour tops.
    I change my impellers every season because of the suspended sand we have here in our rivers, it's cheap insurance!
    Tip:
    (1) Put your drive in gear before you pull the lower unit, so you will have a easy time meshing the lower unit shaft to the crank by rotating the prop.
    (2)Raise your trim up high to provide clearance to remove the lower unit.
    (3)R&R your water pump, grease the new impeller & housing and re-install all new parts and gaskets.
    (4) DO NOT over tighten the impeller housing screws! :frown:
    (5) Carefully guide the water tube when re-installing your drive, I also like to grease the tube end that goes towards the power head.
    (6) Besure to mesh the gear selector (towards front) shaft whene re-installing and DO NOT force anything, if you feel you have to use the lower unit bolts to "pull" it back together, then you do not have the water tube or drive shaft or gear selector shaft lined up. :cry:
    My $0.02
    TV

  4. #4
    Tunnel Vision
    If your going to spend the time to do it, why just the impeller! You have the damn thing apart anyway and the kit is complete!
    Besure to replace the o-rings on the lower pump housing, they come with the kit and it's cheap insurance! :lightsabe
    TV

  5. #5
    Water Romper
    Hey guys,
    Thanks for the advice. I will print all the advice and jump in.
    The motor started running warm over memorial (psychotic) weekend at LaughlinÂ…probably sucked up something disgusting in my water pick upÂ…
    Just an FYI....no 100K Cat here, just a little 18 foot Carrera bought and paid for.
    With a mortgage and ex-wife, I am lucky to have this.
    Thanks again for all the help.

  6. #6
    Tom Brown
    I'm sure you'll be fine, WR.
    You should consider picking up a water pressure gauge. They aren't expensive and it will tell you exactly what's going on with your cooling system. You should have 15+ PSI at 5500 RPM.
    By the way, no shots on your boat here. I run a 1977 Glastron and feel lucky to have it. It's all about getting out on the water and having fun.
    - Tom

  7. #7
    Tunnel Vision
    If it floats it's cooooool!
    good luck!
    TV

  8. #8
    Water Romper
    I'm lookin at "TunnelVisions" twin screw" DCB....maybe after I win the lottery I will get one.
    I've been boating for over 30 years and still love it...

  9. #9
    Forkin' Crazy
    I'll add a couple of things...
    Twist the driveshaft while pushing the impeller housing gently down the shaft over the impeller. This will help fold the impeller's blades and make installation a snap.
    I don't use a prop to turn it to get the driveshaft to mesh, but a remote starter switch w/ NO prop on the gear case. To me, it is easier to handle that awkward gear case w/o a sharp propeller on it.

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