7.5 Mercury New Water Pump won't Pump Water

[sfmiller]

Hopefully someone out there can help me with this problem. I just changed the impeller in my 1978 7.5 Mercury outboard. Now it still won't push water. The key is in place, the fins are facing the right direction, the tube is clear, etc. I have taken the lower unit off, checked it, and re-installed 3 times. I am testing it in an 8 gallon can of water. When I place a hose directly under the intake area it will push water through the line.

Does anyone have a thought of what I might be doing wrong?

Thanks.

 

[James R]

Re: 7.5 Mercury New Water Pump won't Pump Water

Got to have the water pump below the surface of the water not just the in take. Try it.

 

[sfmiller]

Re: 7.5 Mercury New Water Pump won't Pump Water

Thanks James.

I just took a look and the pump itself would be about level with the water. Maybe 2-3 inches below at the most. I'll try to find a deeper drum and give it another try.

-Scott

 

[sfmiller]

Re: 7.5 Mercury New Water Pump won't Pump Water

I put the boat in the lake this morning. The motor started pumping water as I pulled away from the dock. However, it stops peeing water when I drop below 1/2 throttle.

Any thoughts?

Thanks,
Scott

 

[cableguychris]

Re: 7.5 Mercury New Water Pump won't Pump Water

i have a 1971 7.5 hey i need to take my lower unit off i have the two bolts off is there more to it because it's stuck? thanks i have barely any water peeeing out also

 

[steam_mill]

Re: 7.5 Mercury New Water Pump won't Pump Water

I just replaced the water pump on the same vintage motor. Dealer told me there were two different waterpumps for that vintage. Do you have the right one?

I had a similar problem and the pickup tube was not properly inserted.

 

[8075mercury]

Re: 7.5 Mercury New Water Pump won't Pump Water

I think I would check to see if the idle exhaust ports which are right below the lower cowling in the back are plugged up. If this is plugged up, then exhaust is forced in the water intake backing out the water inflow during idle. This is particularly pronounced in a barrel. Try spraying some WD40 or PB blaster or some solvent in the little idle exhaust ports and rodding out with a small wire. Another check to see if this is the problem is to check exhaust and exhaust pressure is coming out of the idle exhaust port when idling in a barrel.

Good luck as these are super little motors !

 

[sfmiller]

Re: 7.5 Mercury New Water Pump won't Pump Water

Thanks for the suggestions.

Chris - mine only has 1 bolt and 1 nut. There is a nut on the back side and a bolt behind the prop (near the intakte).

Thanks again.

 

[JDINNO]

Re: 7.5 Mercury New Water Pump won't Pump Water

Had the same problen with my 9.8. The copper tube from the pump to the block, (the one that slips into the guide tube) got pushed up too far, and wasn't seating in the pump. Grab the copper tube with a pair of pliers and pull it down a bit, it seats into the block the same way it does into the pump.Put some lithium greese on the bottom of the tube so it will slide into the seal on the pump. The guide tube is just that, a guide, the copper has to seat into the gasket on the pump. One way to test the pump is to remove the lower unit and place it in a 5 gal bucket, chuck a drill to the drive shaft and spin to varify pump is working. Good luck!

 

[seany150]

Re: 7.5 Mercury New Water Pump won't Pump Water

my impeller was replaced a couple of weeks ago on my 7.5 merc 1985, took it to a boat mechanic to have it done as the old one was seized on there and there were 2 different types of impeller so wasnt sure which one was the right one. when i put the leg back on it still didnt pump water. took off the leg about 15 times to try and establish what i'd done wrong, turns out the mechanic had lost the little metal plate that sits on top of the impeller. once he ordered me a new one it worked fine.

i also connected a hose to the top of the cylinder head to reverse flush the engine with the leg off, so that i could see if it was circulating the block ok and exiting the copper tube inside the shaft. mine shot out a load of sludge so it might be worth giving this a go too

 

[crabby]

Re: 7.5 Mercury New Water Pump won't Pump Water

replace my impeller.nownwater squirts sometimes and stops.
used water hose to force water from bock to lower unit.
did not remove screen on lower unit.
started motor water flowed then stopped.
what should i do.

 

[BASSIN247]

Re: 7.5 Mercury New Water Pump won't Pump Water

I have a merc 150 xr6 on my boat its a 1999 and has maybe 35 hrs since new fish mainly trolling motor lakes and i just replaced the water pump impeller and the all the gaskets i used the hose and shot water threw the copper line thinking it would pee water but it didnt so i took the line apart at the t and did it that way and the weep hole had water coming out of it this is the 10th time i have had it apart if it doesnt pump now what should i do