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Lower Unit Stiffness

gogittumgogittum Nature CoastPosts: 3,645 Captain
Still grabbing at straws, trying to figure why I'm not getting the rpm's I want.  From other reading I've done and from prop recommendations online, seems to me that the 10 x 14 should be a good fit on my boat/motor, but I'm only getting 4600 rpm out of the 10 x 14.

Also, (don't be too quick to jump on me here) a fully charged 10 amp battery has a hard time starting the motor and cranking speed is low.  My reasoning is that a 10 amp started my 60 hp, 650cc Suzuki V-Strom motorcycle just fine and spun it fast for 2 years that I owned it.....just sold it a year ago.  Seems like same battery should spin a 25 hp, 538cc motor as well.  I carried the jump starter with me the last 2 trips - and needed it on the river on Wednesday.

(the starter button requires a Lou Ferrigno thumb to get action, but that's a whole 'nuther problem)

I've put new impellers in water pumps of the 15 hp Force and the 15 hp Johnson and noticed that I could turn the lower unit input shafts by hand without much problem.  The seals hafta keep water out, so I expect some resistance, but what I got seemed reasonable.

On this 25 hp Suzuki, I noticed that the input shaft is "very" stiff and could only turn it with a heavy glove on and really putting the strain on it.  On the other end, turning the prop with lower unit on the bench did turn it over but needed a lot of force.

Has anyone ever heard of this problem ??  The seller assured me that he'd put a new impeller in there so I didn't check it when I was working on the gear shift - I went in from the prop/gear case end.  Maybe he put something in upside down or something ??

Seems to me that thing is soaking up a lot of horsepower just turning the driveshaft.

Replies

  • chaser48chaser48 San Mateo Fla.Posts: 345 Deckhand
    Battery is a little lite imho,I have a midsize battery on my 25hp yami on the lower unit being stiff I would think as much as you have run it if any problems there would have shown up by now
  • CapnSkipCapnSkip East Central FloridaPosts: 58 Deckhand
    edited October 2021 #3
    Maybe a shim was installed incorrectly when you repaired the hard reverse issue?
  • gogittumgogittum Nature CoastPosts: 3,645 Captain
    CapnSkip said:
    Maybe a shim was installed incorrectly when you repaired the hard reverse issue?
    Watched closely for that and took the computer out there with the exploded view of the gearcase on the screen.  I double checked every piece to make sure of sequence and location as I went.  It's actually a fairly simple setup.....not many pieces.

    It was hard to turn before, and gears turn and shift perfectly now.  Don't think it's down there.
  • gogittumgogittum Nature CoastPosts: 3,645 Captain
    This afternoon, I pulled the lower unit - again - and put it on the bench. Shaft was very difficult to turn. Hah....figure this....I pulled the 4 nuts & washers holding the impeller housing and felt "something" when I popped it off. With the housing off, the shaft turned quite easily - about like others I've worked on and about what I'd expect with the seals on the lower shaft.

    Put the housing back in place - loosely - and still easy to turn. No stacked washers, no missing gasket....nothing I could see that would or could cause binding. Now I'm thoroughly and completely baffled. I threw up my hands and walked away.....tomorrow with a clear head is another day.

    I did notice that 1/4" was missing off the ends of 3 of the 6 vanes of the impeller and they're gone, which means they're up inside the motor somewhere. Tomorrow, I'll pull the thermostat to check function and corrosion and look for those pieces. Also the pee tube if I can access it.

    Suggestions would be welcome.

    New lube went in when I re-assembled it the other day, after I'd also put all new seals throughout. It had shown water intrusion on the previous run. I'll check the new lube tomorrow.

    I also hit the start button after I pulled the lower unit off and it spun fast and started instantly. Hmmm....?? Why can't any of this be simple and straightforward ?? The sticking gear shift problem nearly drove me bughouse before I finally solved it.....simple in retrospect.

    That start button....Arnold Schwarzenegger could prob'ly do well with it, but for a normal human it's a thumb buster. I'd "love" to find one that I can push without dislocating my thumb.
  • CapnSkipCapnSkip East Central FloridaPosts: 58 Deckhand
    Is the cup that the impeller sits in installed correctly into the plastic housing? I'm thinking along the lines that maybe it was installed with the alignment tabs, if it has them, not aligned with the holes that they fit in in the plastic housing thereby keeping it from sitting flush with the housing.

  • gogittumgogittum Nature CoastPosts: 3,645 Captain
    CapnSkip said:
    Is the cup that the impeller sits in installed correctly into the plastic housing? I'm thinking along the lines that maybe it was installed with the alignment tabs, if it has them, not aligned with the holes that they fit in in the plastic housing thereby keeping it from sitting flush with the housing.

    Housing and gasket looked good before I took it off.  As I moved it, it felt like something "let go" but I looked all over the components and could see nothing out of place or that didn't belong there.  Now it seems to turn fine, but haven't bolted it down tight, either.....so far.
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