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75 Merc is killing me

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pissant

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"Hi I need some help here. I h

"Hi I need some help here. I have a 82 7.5 that has a water pump issue. I replaced the complete pump assembly including the impeller. I blew out the intake tube to make sure there were no obstructions. I re-assembled and no tell tale water. I tore it back down and made sure the key for the impeller was in place. It was, so I blew the intake tube again. Re-assembled and still no tell tale. This model has no thermostat and as far as I know, the intake tube should be seating since it is going in the guide tube during assembly. I hooked my air drill up to the drive shaft and spun it to check that the pump was functioning, but at 750rpm the pump didn't really spray an impressive stream of water, but it was pumping.
Before I re-assemble again, could I have a bad seal at the powerhead? When I blow air up the intake tube and seal off the tell tale line I can hear air escaping from somewhere...

Any help is surely appreciated!"
 
The air you can here escaping

The air you can here escaping is proberbly the air traveling out the exhaust ??
there will be someone far more knoledgeable than me along soon to stear you right. good luck.
 
Take a piece of weed wacker li

Take a piece of weed wacker line and run it up the tell tale tube. Sometimes mud daubers get in there and do there thing and clog them up.
 
"Alright, so here is where I&#

"Alright, so here is where I'm at. I pulled the power head and I found the plastic washer with the recess to be in good shape. The gasket between the power head and leg was also in good shape. The intake tube seal seemed to be in decent shape, but the fit wasn't as tight as I would like to see. I did notice that of the six mounting bolts on the power head, two seemed to be somewhat loose. I also found one little remnant of impeller in the intake area of the power head near the intake port. I also decided to pull the exhaust plate and baffle for a closer inspection. With air nozzle, I traced the power head cooling circuits and found no fault. As indicated from an ealier post, water will pass through the exhaust port. I only see this being for an additional measure to create vacuum to assist the pressure type vane pump that this outboard uses. So there is a possibility that the small piece of impeller did block the power head's intake port. I will now need to replace the gasket, seal and recessed washer. Maybe somebody can answer a question for me since I haven't been able to find the spec. How much water pressure will the water pump produce at idle and WOT? Also, I recieved an email from someone who answered "Everyone knows that...." I may not work on outboards daily, but I am a Technician / Engineer by trade in the automotive industry and although I could, I think I speak for everyone when I say arrogance does nothing to help anybody and only makes you look an A&&. For those that are offering their advice, a much thanks is in order! I hope I can offer my help to you one day!"
 
"Remnant piece of impeller can

"Remnant piece of impeller can block the system big time ,did the impeller you took out have bit missing ?.I dont k now water psi for your motor but turning the throttle should be like turning a tap on the more you twist the more psi you get.There should be a constant stream at idle ,it sound like you have done a good job ,however there could be some broken impeller bits causing you this grief ."
 
"I've ordered my parts so

"I've ordered my parts so in the mean while I've enjoyed a few beverages while doing some further checks. I noticed that the intake tube does not fully pass through the pump seal. The ID of the seal is too small to allow it. This means that a bend in the intake tube could mean an improper seating thus causing a loss of pressure. Since at idle (500-750)Rpm the pressure is 5-8psi there could be a loss significant enough to not supply water to the power head as well. Since the power head is off at the moment, I will re-mount the lower unit soon to check my theory. Yes, the pressure will rise at a linear rate with respect to the Rpm. However, the spec did not show what the PSI would be at WOT."
 
"Success! My Merc is now pumpi

"Success! My Merc is now pumping water and to say the least, I am a happy camper. The end result was that by cleaning out the remnant piece of the old impeller was probably the cure. The seating of the intake tube in the new pump seal was potentially an issue as well. I would recommend applying a small amount of grease to the outside of the intake tube to ensure that the tube seats in the water pump seal correctly. Having the power head off also allowed me to do some cleanup and the ability to replace the upper intake tube seal as well. While I was at it, I also lubed the throttle control cables.

On a final note thanks to those that offered their advice on my problem as well.

You will probably hear more from me when I start out on my next project which is my CC 230 Scorpion. This will be my 4th boat restoration project, but probably the most testing of my resourcefulness."
 
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