Can a new impeller be bad?

[hotrod53]

Working on a '77 Merc 500 4 cylinder Thunderbolt. I pulled my LU and replaced the impeller, it was 5 years old and it didn't pee on the test fire. I dropped the LU and the original was cracked on each leg but no broken arms.

After installing the new impeller, I still couldn't get flow. The pee hole was dry, I pulled the block plug between spark plug 2-3 and it was dry too. I pulled the LU again and everything looks right. Gaskets are in the right places, the impeller is set in the proper direction, and the key is between the shaft and the impeller.

When the last impeller was installed, this motor peed on the muffs. In later years, it only peed when in the river. I have not tried to see if it wil pee when in the river assuming it would owe on the muffs when new.

While I had the LU off, I connected a garden hose to the pickup tube and I got good water flow through the block, out the exhaust, and a strong pee stream.

Any suggestions? Can I have a bad impeller that is slipping on the key?

 

[Scott Danforth]

Check the grommet at the power head

Was your waterpump housing in good shape

 

[Sea Rider]

Could have had a mismatch connection between the upper grommet located on top of water pump housing and the vertical water tube that transports water to the powerhead when assembling lower leg back, that's if the impeller key was correctly installed.

Happy Boating

 

[hotrod53]

Can you improperly install the water pump key? Flat side towards the shaft, *** facing out, impeller down over it. This is the first impeller I've done myself and it seems as though either the key is in there and the impeller is on it, or the key isn't there. My assumption is that if the key wasn't in there properly, I wouldn't be able to twist the shaft to work the impeller up into the cup.

As far as the grommet, There's a black grommet in the housing that sits under the gasket and the copper tube pushes into the top of the housing, seems like a no brainer. I know that the lower tube and the upper tube were mated during reassembly.

Again, this is my first one I've done myself, I'm open to any and all suggestions and I appreciate the help.As a precaution, I ordered another impeller and a new key. I'm expecting it early next week. Maybe my 42 year old key isn't what it used to be??

 

[hotrod53]

Scott, The pump housing looked great. The stainless plate is new and I replaced the cup the last time,the gaskets are new as part of the kit. As far as checking the grommet at the power head, not sure about that. I have a copper line coming down and a short one going up. This was a short shaft motor with an extender on it is probably why I have a short little 4" tube at the pump that mates to the main one coming down the housing. I do now for 100% that the two were mated during reassembly.

 

[hotrod53]

One thing that I haven't done, was remove the fiber pump body (15) and replace the gasket and o ring underneath. I seem to recall the guy who replaced the impeller last time said it never gets changed. I have the O ring and gasket (14&13) as part of the kit. What I don't know is can I wiggle it out and will I disturb the oil seal and bearing?

 

[hotrod53]

Bump. I got my new impeller and key yesterday. I can wiggle the water pump base, so I think I can get it out. It worries me that some people had to break theirs to get it out.

 

[hotrod53]

Is this an issue? On the lid of the water pump there is a plastic gasket or o ring. Up inside that tube is where the copper tube connects and it appears to have a rubber bellows like insert. When looking at this picture, should the plastic ring that is sticking out be connected to that rubber insert for the water tube? It doesn't always stick out, I pulled it out, but it appears to be connected to that rubber bellows in one small spot and not the rest. If it's supposed to be connected and is now not, will that cause any issue? I'm thinking it's no big deal, but I'm drawing straws why I'm not pumping water.

 

[BillP]

i've had exactly one bad impeller and the rubber spun on the hub after installation. It didn't pump. This was a 140 V4 omc. You may be experiencing that but i've never heard of mercs doing it. The two mercs I've owned had feeble impellers (compared to OMC and had no margin for wear or leaks at connections either. I would double check the impeller direction.

 

[hotrod53]

Very late update..... I went with a new impeller and a new key, its peeing like me after a 6 pack...lol. I think the problem was what I used to lube the impeller. I was taught to use dishwashing liquid in the cup on first fire up, the rest of the world seems to use grease. I used some blue BelRay motorcycle grease and it primed right up! No more dishwashing liquid for me.