No water through exhaust on 5.7 mercruiser

[rmonheim]

It's not a flat tappet luckily, so I don't have to break in the cam or anything. The coupler is fine, I had it off when I swapped motors and it looked good. If I put it in gear while running, the prop spins as it should. I'm wondering if I just need to run it a little longer and rev it up a little more to get the pump to start sucking. Maybe I'll put the known working old impeller back in just to see what happens.

 

[Bt Doctur]

The impeller does not suck water, it moves water

 

[Rick Stephens]

Even more about how the impeller doesn't suck, it is vented to outside the housing so when submerged the air vents out allowing water in for priming. An impeller cannot pull water up at all, not even an inch. Hence dunking a sterndrive in a water bucket tends to just burn up impellers.

Also, revving the motor does not help. Water supply and the open vent and water should be pushed.

 

[Scott Danforth]

are you trying to pull from a bucket? if so.....stop

the only way to try to pull water from a bucket is to have the bucket big enough to put the whole boat in it and to get the water lever over the outdrive, or at least 4-5" above the pump (center of the driveshaft)

if you are not using a muffs and trying to suck from a bucket......... that is your problem.

 

[rmonheim]

...I am using muffs as specified in the original post. I'm not expecting the impeller to suck up water from a bucket

 

[harringtondav]

Am I just dumb and installed the impeller backwards?....

A mistake isn't 'dumb', unless you repeat it. Also a new impeller doesn't have a correct direction. Either side works installed up. But you must rotate the shaft CW while forcing the water pump housing over the impeller to set the blades in the correct sweep. If you forced the housing over a fixed impeller the blades could have gone every which way. Looks like they may have.

 

[achris]

Did you drop it into gear during any of the tests? If the prop goes round, the driveshaft is turning, and so the impeller is turning. If the prop didn't turn when in gear, you have a drive or coupler problem.

 

[rmonheim]

Reassembled everything with great care after testing the cooling system with the hose. First start up on the muffs and it still didnt seem to pull much water. Went and dunked it in the lake and the manifold/riser/elbow stayed cool to the touch running for about a minute at various engine speeds.

I'm going to consider it problem solved for now. I'm assuming its an issue with my muff/water hose set up. I guess I will pick up a better set of muffs to try, but for now will just run it in the water. Thanks for the help everyone.

 

[Lou C]

I have had trouble with the dual inlet Tempo style muffs sold widely. The rubber is too stiff for it to get a good seal. Get the Merc/Quicksilver ones with the metal rod and clamp. The round muffs are made of more flexible rubber that fit the lower unit better.