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99 8hp not pumping water

tschanne

New member
I picked up a 99 8hp 2stroke recently and got it running and starting fine but I'm having a problem with water not pumping. After replacing the t-stat and a new pump kit it started pumping right away and that lasted for a couple of minutes before it went down to dribble then stopped and was just pumping hot air/steam out the telltail hole. I thought it may be a blockage from calcium deposits so I tore everything apart and made sure all passages were clear and water could flow through.

Just for kicks I took the lower unit with a cordless on the shaft and submerged that in a tub of water and when I spin the shaft no water is pumped out the top of the impeller housing. Took that apart again and all the new parts are intact and in good shape. The impeller is located on the woodruff key as it should and spins with the shaft properly. Also the passage for the water to go up from the pick ups on the lower unit to the pump are clear and clean.

I'm stumped:confused: and can't figure this sucker out.

Please help!!
 
Nothing? I was hoping someone would lend a hand that may have experienced the same problem.

I called a couple of shops and they basically won't help a DIY'er, they'd rather do the work and get the billing.
 
When testing, are you spinning the pump the right way? Is it possible that when testing with it apart, you opened up a port, or valve that left the pump airbound? Is it the right impeller, it should fit pretty snug in the housing at rest.
 
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Thanks for the reply,

There's only five components to the pump on that lower unit, the impeller, impeller housing, housing insert,stainless plate and gasket are all brand new. As I mentioned in my original post, it was pumping on my first try and then stopped after a couple of minutes.

What has me stumped is when I just test just the lower unit alone in a tub with a drill on the drive shaft, it doesn't shoot water out the top of the housing.

Should it pump water when the lower unit is separated from the upper?
 
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Quick question, have you tried taking the thermostat out and seeing if it works then? also when you replaced the impeller did you make sure all the broken pieces (if any) were accounted for? I know I had to use needlenose pliers and a piece of wire to get all the broken pieces from the tube. Some engines have a screen where the water pick up is..you can remove it to ensure the passage to the impeller is clear. Good luck!
 
Quick question, have you tried taking the thermostat out and seeing if it works then? also when you replaced the impeller did you make sure all the broken pieces (if any) were accounted for? I know I had to use needlenose pliers and a piece of wire to get all the broken pieces from the tube. Some engines have a screen where the water pick up is..you can remove it to ensure the passage to the impeller is clear. Good luck!


I did try running it with out the t-stat and had the same results- no water pumping and when I took the head cover off to replace the stat the water passages were dry (and hot!)

My problem must be the pump but with the new kit installed and the fact that it did pump for a few minutes, I'm at a loss. I guess the last resort is to buy another impeller/pump kit and try that. I keep thinking it must be something obvious and simple that I'm over looking but after taking it apart and reassembling it a half a dozen times it's really not that complicated.
 
I wouldn't buy another pump kit just yet so long as you are sure it was the right size. When you installed it are you CERTAIN the veins on the impeller were ALL twisted in the right direction? These impellers fit TIGHT and when inserting them you need to twist them in the right direction when setting them in that housing. Put them in the wrong way or have a few veins on the impeller that didn't twist the right way and they won't pump. The thermostat up top only opens and closes with temperature but it needs water pressure and hot water around it for it to open. It will only be surrounded with water provided by the pump if it is working and pushing water up to everything. The tell tail pee hole will spit water regardless of the thermostat being open or closed... it starts spitting as soon as the engine is fired and the water pump builds pressure that pushes water up to the block. Make sure your fins on the impeller are bent the right direction. If you got 4 of 6 in the right direction and the last 2 are wrong.. no pressure. I also know that when an impeller goes the fragments of rubber can work their way up into the engine and block vital water pasages but that doesn't seem to be your problem as you can't get flow from the lower unit being turned by a drill driver. Your problem seems to be in the lower unit. Take it apart and check for scraps from the old unit that could be hiding down here and MAKE SURE all veins on the impeller are properly seated.
 
I wouldn't buy another pump kit just yet so long as you are sure it was the right size. When you installed it are you CERTAIN the veins on the impeller were ALL twisted in the right direction? These impellers fit TIGHT and when inserting them you need to twist them in the right direction when setting them in that housing. Put them in the wrong way or have a few veins on the impeller that didn't twist the right way and they won't pump. The thermostat up top only opens and closes with temperature but it needs water pressure and hot water around it for it to open. It will only be surrounded with water provided by the pump if it is working and pushing water up to everything. The tell tail pee hole will spit water regardless of the thermostat being open or closed... it starts spitting as soon as the engine is fired and the water pump builds pressure that pushes water up to the block. Make sure your fins on the impeller are bent the right direction. If you got 4 of 6 in the right direction and the last 2 are wrong.. no pressure. I also know that when an impeller goes the fragments of rubber can work their way up into the engine and block vital water pasages but that doesn't seem to be your problem as you can't get flow from the lower unit being turned by a drill driver. Your problem seems to be in the lower unit. Take it apart and check for scraps from the old unit that could be hiding down here and MAKE SURE all veins on the impeller are properly seated.

When I reassemble the pump I make sure to turn the shaft clockwise as I'm setting the housing down onto the impeller to ensure all the veins are pointing in the same correct direction. Also when the impeller and bottom plate and gasket are off I can see clear through the water passage to the pick up holes so I know that's clear as well.

Just for S & G's last night I adapted a section of garden hose to the water tube on the upper unit and water flowed well out the tell tail pee hole so that eliminated the upper unit as part of the problem.

When I'm testing the lower unit with the cordless, I'm spinning the shaft clockwise and have the lower unit submerged in water so that it's just covering the cavitation plate and the pick ups are completely under water. Is for some reason that not far enough?
 
How much water was in your test bucket / tank ?-----Was the water 6" above the pump ?


The water was just over the cavitation plate/fin above the water inlet. That would make it actually below the level of the pump. Does the water have to be above the level of the pump in order to work?

Does this theory sound correct?

When I tried it after the rebuild the first time it did pump for a couple of minutes but I may have lost enough water out of the trash can from the pisser and splashing etc that the water level then went below the pump and that's why it stopped pumping up and coming out of the tell tail piss hole.

I'll put the lower unit back on tonight and try it again with the water level well above the pump.

We're making progress guys, thanks for the tips and help. I appreciate it:)
 
Sink the lower unit as deep as it normally would be in the water on the boat and try it. These pumps are not self priming... they have to be under water to pump or need earmuffs hooked up to a garden hose that forces water under pressure through the inlets and up to the pump. The cavitation place should be fully submerged at rest for the pump to work.
 
Success!!

I reattached the lower unit and this time submerged it in the test tub well above the level of the pump and Viola! , it pumped beautifully and works like a charm. I was hoping that my issue was something simple and obvious.

Thanks so much to all for your help, i
 
You're welcome and our Silver Level contributor RACERONE deserves the credit as he suggested the same thing I did later on. We are all happy that you are on your way and the problem is fixed. Do send RACERONE a thanks. He called it before I did. Then, go have some fun!
 
Dead on!!

The water level wasn't high enough to allow the pump to prime. I increased the level and all is well.

Good call and thanks for your help!

thank god I came across this forum I was having same problem but this was the answer for me also. amazing what 2 more inches of water can do.
 
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