Irregular output from Tell-tale w/ new impeller

J

johnyi

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Joined
Apr 20, 2002
Messages
22
Just changed the impeller on a 88 Yamaha 150. Now the telltale output fluctuates from one second to the next. It never did this before. Is pulsation normal after installing a new impeller?<br /> :confused:
 
B

Backlash

Chief Petty Officer
Joined
May 16, 2001
Messages
586
Re: Irregular output from Tell-tale w/ new impeller

Hey Johnyi,<br />No, pulsation isn't normal. You should have a steady stream out of that Yamaha. If you're not having any overheating problems, I'd say there's a little something clogging the telltale passage. Try blowing compressed air back through the hole as you're running the motor (in the water or with muffs on of course). Very often, this will clear up the situation nicely.<br />Backlash
 
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johnyi

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Apr 20, 2002
Messages
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Re: Irregular output from Tell-tale w/ new impeller

Thanks Backlash,<br />I checked the hose and there's no obstruction. I also ran the motor in a barrel and found the pulsation would stop when the water level reached the anticavitation plate. Three or four inches below it would start again. I didn't tighten the plastic pump housing bolts too much as I heeded the Clymers manual warning about potential cracking. Could it be sucking a little air when it has the opportunity? I used a new gasket, o-rings, and perfect seal on everything. Should I launch or open it up again?
 
B

Backlash

Chief Petty Officer
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Messages
586
Re: Irregular output from Tell-tale w/ new impeller

Hey Johnyi,<br />Sorry for the delay...been busy away from the computer. It sounds like you did everything right when you replaced the impeller.<br />Were you running the motor on muffs when the pulsation you described in your first post occured? If no pulsation when the water is at the cavitation plate level, you're probably OK. I'd put it in the water and give it a test drive. :) <br />Backlash
 
J

johnyi

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Apr 20, 2002
Messages
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Re: Irregular output from Tell-tale w/ new impeller

I was running the motor on muffs when I first tested the new impeller. It never pulsated on them before the change. Is it possible that the new pump moves more water and is running away from the water supply when on muffs? Could the pump be sucking a little air until its totally submerged and, if so, does it matter? I also noticed that when the thermostats open the stream gets very weak for a second and then resumes. I'm leaning toward dropping the lower unit and retorqueing the waterpump housing bolts. Your thoughts are helpful and greatly appreciated.<br />Thanks again,<br />John
 
B

Backlash

Chief Petty Officer
Joined
May 16, 2001
Messages
586
Re: Irregular output from Tell-tale w/ new impeller

Hey Again Johnyi,<br />It's possible that you're sucking a little air. Did you use any sealer between the pump housing & base plate when you installed the new impeller? If not, a little OMC Type M (or equivlent)will eliminate any air leaks. The pump housing must be airtight to work properly. Let me know how you come out. :) <br />Backlash
 
J

johnyi

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Joined
Apr 20, 2002
Messages
22
Re: Irregular output from Tell-tale w/ new impeller

Thanks again Backlash,<br />Sorry I took so long to reply. I still don't have a final outcome. Will probably launch, as is, within the next couple of days. If she doesn't overheat, I'll rebuild it again next Spring (using a torque wrench). If she does, I'll have made a little extra work for myself. Hope the fish are biting! Thanks,<br />John
 
D

DJ

Guest
Re: Irregular output from Tell-tale w/ new impeller

JohnnyI,<br /><br />I think you answered your own question when you put the foot into a barrel. The new impeller was probably pulling more water than the muffs could supply. Especially if the muffs were the variety that only feeds one side.
 
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