Water won't pump on idle

[Slaya]

Just replaced the water pump on my 50hp outboard went to start it up and the water won't pump when its idling. I can see exhaust come out of spit hole on idle. But water does spew out when the throttle is up (half way or more), forward and reverse.

 

[Texasmark]

Obviously as the RPMs increase the volume and pressure of the pump increase. You didn't say if your Tell Tale squirted water at idle prior to your replacement. Knowing that would help. The engine should show a reasonably strong stream at idle...no dribble nor lack.....unless the TT is plumbed off the thermostat....if your engine had one. In that case, you would have to wait for the stat to cycle to get water.

Some engines are plumbed off the exhaust manifold water jacket....flat plate on the Port (left facing forward) side of the engine block. That provides water to the TT 30 seconds give or take from start up at idle.

You didn't mention the condition of your impeller. Was it intact, or did it have pieces missing....pieces that could clog water ways. Did you have seals in the kit that you didn't get in the right place when installing. Did you get the water tube from the pump to the bottom of the engine block installed properly. Were you operating in weed infested water whereby you could have ingested foreign objects in the water path from the pickup to the TT output?

 

[racerone]

Are you testing in a bucket , on a hose or in the lake ?-----Year and serial # is ??

 

[Slaya]

Serial #2739070, I have tested in a bucket as well as muffs, it's a 50hp 500 thunderbolt motor. I had replaced the impeller as well as gaskets. Because the old impeller had been torn to bits, prior to the old impeller shredding it had squirted out fine when idling. I have ran the motor for around 5 minutes tops at idle and still nothing. The new impeller is still fully intact, when the motor is off of I spin the prop I can hear the impeller push the air like it should. I'm thinking it may be clogged somehow and if you guys agree, how would I unclog it? I've tried squirting water up the copper line and down the squirt hole.

 

[Linkedit]

I’m quite new to boats so take this with that in mind....

I had no water coming or do my ‘70 650 but it felt quite cold, I blew compressed air up the tell tale and I could hear something unplug. Tried again and water came out.

 

[flyingscott]

Did you line everything up when you replaced the waterpump? Is the drive pin in the impeller? Maybe double check your work there.

 

[Slaya]

I have checked it multiple times and had 2 other people take a look who are more experienced with outboards, everything looks right. Pin in place, and all lined up, I've also blown compressor air through the tell tale and it sounds like it comming out the lower unit right below the engine and not by the impeller but I'm not quite sure if that's normal or not. Just today we took off the lower unit and sprayed water through the tell tale. The majority of the water came out of the shaft and not through the copper line that connects to the water pump.

 

[Texasmark]

If the engine is out of the water and has drained, injecting air into the cooling passages will exit the midsection and the prop. My bet is you have a piece of that old impeller stuck in the wrong place. Might keep your air testing going and maybe in time it will dislodge. Might pull the hose and hose barb off where the TT hose connects to the engine block and run the engine on muffs with full hydrant water pressure. In the interim, just keep your hand on the engine block and feel the water that does come out of the TT.

I don't know if that engine has a thermostat or not. Old original 4 cylinder Mercs didn't have one. If you do have one opening temp could be 100 to 143F. Not hot enough to scald you and 143 would be like the hot tap in your house for an idea how hot is 143...USA domestic hot water with the thermostat in the Normal position. In short if you can keep your hand in the tell tale or on the engine block, you aren't overheating....just have a malfunctioning monitor.

 

[Slaya]

Thank you guys for your help, I will continue running air and water through it hopefully it will dislodge.

 

[flyingscott]

Where did uou get the impeller from? Is it a cheap chinese one? The air coming out from under the block is normal. Most of the water pumped through the block freefalls down through the leg. This allows it to cool the exhaust so it doesnt burn up the pump and seals.

 

[The Force power]

Something you could try......

With the LU removed attach an old garden-hose to the copper pick up tube & the other end hooked to the tap.
Turn on tap,you don't need to run the engine(it will loud as hell if you do lol) see if water makes it to the head / water coming out of the Tell-tail

AND/OR

Take stiff thin steel wire/rod bent the end into a small angle or hook shove it up the copper-tube as you rotate the rod and sweep the tube

good luck