Lower Unit Stiffness

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gogittum

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Aug 27, 2020
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Location
Nature Coast of Florida
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 Suzuki 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.
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it is possible that the vanes on the new impeller are all bent the wrong way. This would result from turning the driveshaft the wrong direction during installation. There's more resistance to rotation when this occurs. Don't know any way to check except by disassembly.
Good luck
 

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