Tell tale volume

[Augie51]

I replaced water pump impeller on an older Merc 140. Fired it up and got a mediocre stream. Seems it should be squirting out pretty good. I checked for plugs w/ wire and back-blew from the exit hole w/ air. Any suggestions? Does it require a break in period? Maybe it's OK?? Thanks

 

[Texasmark]

Re: Tell tale volume

No break in period. It's good to go right out of the box so to speak. Apparently it is less than what you had before or you wouldn't be questioning it. Possibly you dislodged some crud in the process of the repair or you may not have gotten your water outlet tube plugged into the bottom of the power head adequately and it's leaking and reducing the volume to the block.

On those older engines there is nothing to hold the soft copper tube in place so you need to start with it straight and ensure that you have seals at both ends.

The bright side is that you just had it apart and even though it is a pain to go back in, how to do it is fresh in your mind and all your fittings are fresh fit meaning they will separate easily.

While you have it apart, I'd put the water tube in the block and hook the water hose up to the end of it and check your tell tale then.

Did you install your water pump parts correctly?

My 2c,
Mark

 

[Moody Blue]

Re: Tell tale volume

Is the motor running on muffs? If so, don't expect much of a telltale stream.

Big difference when you run it IN the water.

 

[Augie51]

Re: Tell tale volume

I ran the motor in a tank and it seemed to produce a little more volume. It still spurts a bit. I blew back thru the 'tale hole and heard air rushing in the driveshaft housing. It seems that the air should be going back in to the water pump so one wouldn't hear it very well. Could this be an indication that the water tube is not properly lined up and set on the top of the water pump, explaining the rushing air and the inconsistent flow? Think maybe I need to drop the lower unit and check that out. Thanks much

 

[Texasmark]

Re: Tell tale volume

I ran the motor in a tank and it seemed to produce a little more volume. It still spurts a bit. I blew back thru the 'tale hole and heard air rushing in the driveshaft housing. It seems that the air should be going back in to the water pump so one wouldn't hear it very well. Could this be an indication that the water tube is not properly lined up and set on the top of the water pump, explaining the rushing air and the inconsistent flow? Think maybe I need to drop the lower unit and check that out. Thanks much

That is what I was eluding to. On older engines you have to stab the copper pipe whereas on later engines Merc finally figured out that if they would support the lower end of it thus holding it in position it would be much better for all of us....so they did.

I used to start with the tube bent out straight to get the max length then bring the LU up into position. It is easier to stab it in the block first from a visibility standpoint, but the mechanics of the process seem to favor having it mounted in the WP and blindly stabbed in the block opening.

However, the block water discharge is down through the mid section and with no thermostat and with exhaust mainfold dumping there also you could have the pipe correctly connected and still hear what you heard. Oh, water pressure from the pump is on the order of 3-10 psig. Your hose is up around 70. Big difference in troubleshooting.

Mark