7.5 Merc not peeing

[Throbbin Rods]

I have a 7.5 HP Mercury, the word Lightning is embossed on the side iof the bnlock and there is a sticker above that that says Comet. Serial Number is 6178247. I put a new impeller in it (the old one shredded) and used compressed air to blow out all the passages then replaced the impeller and the key. Put it all together and it won't pee out the telltale, it occasionally spits but it is very sporadic. I took it apart two more times looking for an error. The water tube is properly installed. I chucked the main shaft in my cordless drill and submerged the lower unit, and under power it was pumping water up out of the output hole. I put my thumb over it and there was decent pressure behind it. I am kind of at the end of my knowledge. Any ideas? Does this motor have a thermostat? Also, can anyone tell me what year this motor is?<br />thanks very much

 

[Nandy]

Re: 7.5 Merc not peeing

I have a different motor that does not have a thermostat. When I was trying to isolate my problem to a plug water system or the impeller I used the garden hose and attach it using another plasitc hose to the copper pipe. Turned the water on and never got water out of the water ports. When I open my motor the water some grooves where the water use to run were pluged.<br />I hope that you got the idea as it is a little complicated for me to describe. Let me know if you want me to be more detailed.

 

[Throbbin Rods]

Re: 7.5 Merc not peeing

Nandy<br />I didn't think asbout using the water hose to try to push water out the pee hole - I will try that tomorrow if it doesn't rain<br />thanks

 

[Backlash]

Re: 7.5 Merc not peeing

You've got a 1982 model. Is the engine overheating? If not, it's most likely a blocked passage. With the engine running in water, blow compressed air back through the "pee hole" and see if it clears the blockage.<br />Backlash

 

[Throbbin Rods]

Re: 7.5 Merc not peeing

Backlash<br />I already tried that - it goes through the motor and makes buibbles in the water - I am almost thinking about replacing the impeller housing and see if that helps - there was a lot of debris from the old impeller in there and I am sure I got it all out but... Maybe I will try shooting weater upo the tube under pressure and see if it comes out.<br />thanks for the info<br />Throbbin Rods

 

[emckelvy]

Re: 7.5 Merc not peeing

You may have chunks or silt buildup in the water jacket; if you don't get a real strong flow of water out the peehole and also down the center leg of the motor when you hook up a hose to the water tube, you'll want to pull the cylinder block water jacket cover (the one at the back of the block with the spark plug holes in it).<br /><br />I've seen silt buildup so bad inside, around the cylinder liners, that water couldn't circulate out of the block. This'll impede the peehole flow and cause sporadic stoppages.<br /><br />Scrape all the deposits off, blow out with air, then flush with water.<br /><br />Failing all that, your upper water tube grommet may be squeezed shut, blocking flow of water. You'd need to pull the powerhead to replace that grommet.<br /><br />HTH and Good Luck...........ed

 

[Throbbin Rods]

Re: 7.5 Merc not peeing

Thanks Ed<br /><br />I'll try that tomorrow - right after I put the big boat in the weater for her annual shake down cruise.<br />rgds<br />bill