Mercury 7.5 not peeing

C

Cgarski1

Cadet
Joined
May 4, 2025
Messages
6
Hello all, I have a 1973 mercury 7.5 hp that is not peeing water. I replaced the impeller, tested it with my drill to make sure it was pumping good. It was. Still no water just a dribble with alot of steam. So I replaced the water jacket gasket. Still dribbling water and steam. I see alot of people saying to back flush the system with air and water, how do I go about doing that? Or does anyone have ther suggestions to try? Also serial number is 3492203 if someone asks
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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How deep is it in the bucket? Water needs to be 8" above the lower unit
 
R

racerone

Supreme Mariner
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Dec 28, 2013
Messages
38,579
Plastic washer at the top of the water tube could be blocking the flow.
 
R

racerone

Supreme Mariner
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Dec 28, 2013
Messages
38,579
Simple job of removing the powerhead.----Remove horseshoe cowling , 4 screws.-----Remove 6 nuts ( 7/16" wrench) and a few hoses.----Powerhead lifts off.----Will need the gasket and improved cup washer.
 
K

keithb7

Seaman
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Dec 16, 2024
Messages
70
When you replaced the water pump and reattached the lower leg, are 100% sure you aligned the shorter white plastic tube up over the copper tube that runs up inside the leg? Can be easy to overlook. Ya gotta guide it up over the copper tube inside.

Also consider that there are special rubber seals to seal up the connections at the short copper pipe, the pick-up tube down above the prop. If you have no idea how old they are, great time to replace them with the lower leg off.
 
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keithb7

Seaman
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Dec 16, 2024
Messages
70
The white plastic alignment tube mentioned above is circled here in green. 2 special joint water seals are circled in blue.

The water pissing out of these seals won’t help you much. Gotta contain the water within the lines to maintain pressure up to the top where the engine is. The waterpump sucking in water with leaks, then pushing up hill with plenty of leaks is bad.

IMG_2337.jpeg
 
C

Cgarski1

Cadet
Joined
May 4, 2025
Messages
6
keithb7 said:
When you replaced the water pump and reattached the lower leg, are 100% sure you aligned the shorter white plastic tube up over the copper tube that runs up inside the leg? Can be easy to overlook. Ya gotta guide it up over the copper tube inside.

Also consider that there are special rubber seals to seal up the connections at the short copper pipe, the pick-up tube down above the prop. If you have no idea how old they are, great time to replace them with the lower leg off.
Click to expand...
Yes I made sure the copper tune was in whe plastic one, I'll replace those o-rings once I figure out how to lol
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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you basically need the water half way up the transom clamps. as in the outboard sitting in a garbage can.
 
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