115 HP 4 stroke water pump issue

[john303]

I have replaced the water pump impeller on a 2007 115HP 4 stroke Mercury outboard. When the motor runs it does not seem to pump water. I have taken it apart a few times but see no problem. I have followed the shop manual and replaced the impeller and gaskets. The only odd thing is the picture in the manual shows the impeller flexed as though the rotation is counter clockwise while I understand the motor to rotate clockwise. With the motor running on ears neither the telltale nor the outlet to the pressure gage register any flow. When I put a hose up to the filler tube with the lower unit off there is a water flow at both points.

Any ideas, Am I assembling something wrong?

Thanks for your help

[boats.net]

Did you varify that the impeller key is still inserted? Other than that make sure the water tube is sealing both top and bottom.

[john303]

Thanks for your help, I think you are on right track.

The key seems to be in place. There is some resistance from the impeller when turning the pump housing before screwing it down.

The manual suggests that the water tube should be installed into the leg with the beveled end down to receive the pump outlet. My next attempt is going to be putting the water tube onto the pump and then reinstalling the leg. This is to reduce the chances that the tube gets pushed up so far that a connection isn't made to the pump.

I am out of ideas after this. Any other thoughts?

[john303]

Some success

Reinstalled lower unit with water tube on pump. The tube may have been pushed up too high so this is likely my fix. Telltale shows water flow but not powerful. Gage that shows water pressure reads 0 at idle, a bit more at higher RPM. When new the gage read much higher. I guess this is ok for now but is not as it should be.

Any ideas on how to get the pressure back to where it should be? Am I correct in believing that the impeller blades in the parts diagram are bent the wrong way?

[boats.net]

If you are running on water hose flusher may not see any water pressure, try running in water to see if get pressure. May need to check thermostats are not stuck open and the pressure control valve is not stuck open.

[john303]

I think we are getting there

I have been running it with hose ears, that should only feed the water pump from below.

Tonight I took out the thermostat, broke the housing getting it off, but took it out. I cycled it a few times in a pan of water on the stove. It takes a lot more force than the spring can generate to close the thermostat. The travel is .300" but you have to push quite hard to get it to retract when cold. I believe this means that a sticky thermostat is likely to be the problem. This also sounds like the motor water pressure will be lower at full temperature when the thermostat is open and higher when the motor is cold, which I did not note in the past.

You mentioned a pressure control valve. I can not find such a part. My model number is a 115ELPT4S SE#1b429xxx. The manual, 90-899185 906, under general specifications , cooling system lists "Water cooled - thermostat with pressure control". Is there a pressure control valve on this motor? If so where is it?

Also the manual shows a strainer fitting in another cooling line that comes out of the block below the thermostat. What is a strainer or strainer fitting, could it be a problem and does it need to be maintained?

Many thanks for all your help

[boats.net]

It is in the starboard side outer exhaust housing on the top.

[john303]

???

Are you saying that there is a pressure control valve, or just a thermostat? I don't see a pressure control valve in the parts list. If there is one please provide a part number so I can locate it. Same questions for the strainer.

Thanks for your help

[boats.net]

It is number 26,25,24,23 in the following diagram.

2006 Mercury Marine Mercury Outboard 1115F13FN CYLINDER BLOCK Diagram and Parts

[john303]

Different Parts List

Mercury Parts US told me they couldn't look up my serial number. They sent me to the Mercury customer service help line and they in turn sent me the link below which contains schematics that are different from the one you sent me. The "new" schematic does not seem to show a pressure relief valve or a strainer unless I missed them, where the one you sent does. The manual that I referenced previously, has a picture like the "new" one. It does not seem to have a pressure relief valve or a strainer either. However in the manual on page 4A-71 the lower picture shows a Strainer fitting on the starboard side of the block above and aft of the oil filter and the oil pressure sensor and below the thermostat housing.
So the questions are; does my motor have a water pressure relief valve and if so what is it's location and part number. What is a strainer fitting and does it need to be maintained and can it be part of my water pressure problem?


Marine Parts Plus Mercury 4 Serial 115 EFI 4-STROKE 898101362

Thanks for your help

[boats.net]

Which one looks like your motor? What is your serial number again? The end was removed.

[einar]

Running efi 115 on trailer to test before launching. No cooling water. Trying to remove thermostat to test it and also check for water flow to houseing. Not able to open thermostat houseing. Any tips or guidance?
Einar