1984 mercury outboard 7.5hp not pumping water

foothill gary

Recruit
Joined
Jul 7, 2009
Messages
2
why am i not seeing water come through the pee hole. yea i did change the impeller and tested it with a drill on the drive shaft. pumping then.. also ran a water hose into the copper line in shaft ---water came out of little pee hole--both directions---. NO CLOGS ANYWHERE THAT I CAN SEE. What"s up????? just spitting hot gas and smoke. NO the impeller is not ruined yet I checked it 4 times. AND--- for sure--" installed it right"-- into the copper tubing going up the shaft. thanx-----GARY........
 

albertaborn

Cadet
Joined
Jun 29, 2009
Messages
26
Re: 1984 mercury outboard 7.5hp not pumping water

i have the same problem i have done all the same things and its driving me insane.ive even went to the point of putting it all together w/o pull start and putting a drill on the flywheel w/o spark plug and it doesnt work but take the power head off and drill on the drive shaft and it works.i got a new impeler too.i can squeeze water up the tube with the head on and it works.its like putting the head on fxxx it up.its also like exhaust maybe gets into the system.ive put new gaskets with a skiff of gasket maker and nothing. im out of ideas and ready to buy everything for the cooling system
 

7920hpMercury

Petty Officer 2nd Class
Joined
Mar 13, 2009
Messages
111
Re: 1984 mercury outboard 7.5hp not pumping water

Here is a thought for you to try assuming water pump is pumping & water passages are clean. The intake on these motors is through a little screen on the underside of the anticavitation plate right above the prop. If your idle relief holes which are right below the lower cowling in the rear are plugged up with oil/exhaust goop, then when you are idling, all of the exhaust goes through the prop hub and bubbles up into the water intake. This is particularly noticeable when you crank it in a barrel. If you take it out and run it in forward in a lake, then the exhaust is blown back and the water picks up and flows fine. If this is the case, then you need to pull the powerhead and clean out the idle relief holes. Or you might can get the holes cleaned by using some solvent and rodding it out and not have to pull the powerhead. Good luck and hope this might help.
 

albertaborn

Cadet
Joined
Jun 29, 2009
Messages
26
Re: 1984 mercury outboard 7.5hp not pumping water

i thought the exhaust reliefs where under the powerhead.for example if i have the lower half off and squeeze water up the copper tube i can see water come out these reliefs. at first this seemed strange as i thought all the water should exit oly by the pee hole.im sure the reliefs are clean as ive had the power head off 20 times.every thing seems fine when i pump water up the tube or when pump up with a drill with the head off,just when its all back together it dont work.it seems like im getting exhaust out he pee hole but im not sure
 

foothill gary

Recruit
Joined
Jul 7, 2009
Messages
2
Re: 1984 mercury outboard 7.5hp not pumping water

cleaning out the releif holes with solvent and wire worked for water flow a little bit . Have to rev engine to get real water flow to happen. Still not coming out on ldle. Pulling power head???? Do I have to take the powerhead apart? Yes the relief hole was very clog up--- by the way.. Thanx.
 

Spoonman

Recruit
Joined
Jul 8, 2011
Messages
1
Re: 1984 mercury outboard 7.5hp not pumping water

I had the same problem. Couldn't figure it out. Took the water pump apart 3 times and lower unit about 7 times off. Tried compressed air at the pick up tube and at the pee hole at it seemed fine. Had it fixed and it ended up being zebra mussels in the power head clogging the cooling passages.
 

quicktach

Petty Officer 1st Class
Joined
Aug 24, 2012
Messages
394
Re: 1984 mercury outboard 7.5hp not pumping water

Thermostat working ?
 

owens1974

Recruit
Joined
Jul 17, 2014
Messages
2
it is the copper water tube problem. you thought it is in place but actually it is not, there must be one open has been left open, that was why you only saw smoke but not water coming out. Plug the tube tightly to the powerhead first, and use the clip to support the tube in the right position before you insert the LU into the case, turn the propeller and the shift lever to make sure the crankshaft and the gearshaft synchronized with the holes first, so you can only feel the friction coming from the water tube when you insert the LU into the case, or, you can use an examination mirror (or better a X-ray, CT scan, if you can:) to make sure the copper tube is ready to be plugged into the water pump.
Remember, once you eliminate the other possibilities, like failure of water pump impeller or the whole water pump, cooling passages clogging..the only reason for the problem of seeing smoke but not water coming out of pee hole is the problem of the installation of the water tube..
 

owens1974

Recruit
Joined
Jul 17, 2014
Messages
2
it is the copper water tube problem. you thought it is in place but actually it is not, there must be one end has been left open, that was why you only saw smoke but not water coming out. Plug the tube tightly to the powerhead first, and use the clip to support the tube in the right position before you insert the LU into the case, turn the propeller and the shift lever to make sure the crankshaft and the gearshaft synchronized with the holes first, so you can only feel the friction coming from the water tube when you insert the LU into the case, or, you can use an examination mirror (or better a X-ray, CT scan, if you can:) ) to make sure the copper tube is ready to be plugged into the water pump.
Remember, once you eliminate the other possibilities, like failure of water pump impeller or the whole water pump, cooling passage clogging.etc, the most possible reason for the problem of seeing smoke but not water coming out of pee hole is the problem of the installation of the water tube, do not waste time on removing powerhead. Good luck!
 
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