'88 80hp Merc Issue

[MN Sun]

I am a long time reader of this awesome forum and am posting for the first time!

I have a 1988 Mercury 3-cyl 80hp that has me confused. I am no rookie to engine maintenance, but this has me baffled. I recently changed the impeller assembly on this motor after noticing the tell-tale was not putting out any water.

After I installed the new assembly I got a strong steady stream from the tell-tale at idle and low RPM, but I don't see anything coming from it at WOT. This is my first Mercury and wondering what I may be missing.

Thanks everyone for the great forum and any thoughts you may have on my issue.

-Dan

[aussieflash]

On muffs or in water?First thing is to run and stick wire or similar item into tell tale to make sure no blockages which often occur.

[oldman570]

You should have a good flow of water from the tell tail all the time. Was all of the old impeller there hen you replaced it? Did you get the little key back in the new impeller ? Like aussie stated run a wire or weed eater string up the tell tail to losen any blockage. Has the motor run any time without water even 30 seconds? Was the cup in good shape or did you replace it when doing the impeller? All these will effect the water flow.
Oldman570

[Faztbullet]

Check the poppet valve.....

[MN Sun]

You should have a good flow of water from the tell tail all the time. Was all of the old impeller there hen you replaced it? Did you get the little key back in the new impeller ? Like aussie stated run a wire or weed eater string up the tell tail to losen any blockage. Has the motor run any time without water even 30 seconds? Was the cup in good shape or did you replace it when doing the impeller? All these will effect the water flow.
Oldman570

All of the old impeller was there (although worn and quite ridgid). I did replace the plate beneath the impeller as it had a slight groove in it, but not the cup as it looked to be in good shape. I pushed a wire into the tell tail and even took the hose and fitting off to check for blockage.

I have to assume the motor ran for a short time without water coming out, though I did not get an overheat alarm. I did a compression test the next day to check for any damage and had 130 psi on all three cylinders.

One thing I noticed when I took the lower unit off was there was no seal between the drive shaft and the pump cup. The kit I bought didn't have one in it either. I thought this was odd and looked at my parts breakdown and no seal was shown on it. Is this correct?

Also, if I am checking the poppet valve, what am I looking for?

Thanks a bunch guys for all the imput, I REALLY appreciate it!

[oldman570]

I have the same setup as yours and there is not a seal on the top of the waterpum on mine neither as the ring on the impeller and the pump housing is suppose to make the seal on those motors, Enginers design. The popit valve is under the thermastat housing and is the larger of the one there, it should be closed till the motor gets up to higher RPM and the thermostat opens and pressure from the pump opens it and lets more flow thru the motor. Sometimes they will be stuck in one position and not work as intended. Happens on salt water motors often that are not flushed clean after use. I ALWAYS replace the complete pump, including the cup, on mine just because of the design.
Oldman570

[MN Sun]

I have the same setup as yours and there is not a seal on the top of the waterpum on mine neither as the ring on the impeller and the pump housing is suppose to make the seal on those motors, Enginers design. The popit valve is under the thermastat housing and is the larger of the one there, it should be closed till the motor gets up to higher RPM and the thermostat opens and pressure from the pump opens it and lets more flow thru the motor. Sometimes they will be stuck in one position and not work as intended. Happens on salt water motors often that are not flushed clean after use. I ALWAYS replace the complete pump, including the cup, on mine just because of the design.
Oldman570

Thanks for the great advice!

I will be checking the poppet valve and getting a new pump cup to replace the old one.

I'll post the outcome in a couple days.

Again, thanks guys, for all the help.

-Dan