5 hp Mercury New Impeller wont pee at idle

So as title says, impeller took a dump and no pee. Replaced it and everything seemed to go fine. Start it up and it pee'd very strong. Except when I dropped to an idle. Then nothing. Give it any gas and it goes like a race horse.

There is no thermostat. It always had a decent stream at idle before. Only thing I can think of is something did not get sealed correctly? Not enough pressure at idle, but great when any gas applied.

Thoughts?

Going to tear into it again tomorrow.

I was going to suggest looking into the water tube assy. I'd also trace/snake the water tube from the pee exit to the block. I had one do this and during DISassembly, I must have loosened something somewhere (saltwater use OB). And I found a small blockage where the pee tube met the block.

FWIW on an 80s 6hp Johnson that had a head full of salt deposits, I removed the LU, turned it upside-down and filled the water cooling passages w/ cheap while vinegar and let it sit for 2-3 days. Flushed out and put it back together and she ran like a top!

Will do! THanks

Took it apart multiple more times.. ugh. Still wont pee at idle. Cant figure it out.

I'm done with it though. I just raised the idle until it stayed a steady stream. Fish opener is this next weekend here. Hopefully that will be good enough for now. Just a little faster troll.

Don't know on your motor, but the ones I've messed with were thermostatically controlled cooling systems. Seen many a motor with a FUBAR impeller. Impeller came apart. Pieces of the vanes plugging a passage somewhere. On the ones I've messed around with, I like to pull the thermostat out, leave the cover off and then start the motor. If there's anything in that area, it'll come out with the water. If its' in the water tube, it's just stuck there until it's back-fed to blow it out from the top down. I tend to use a blow gun and compressed air into the pee hole with the foot removed, but you don't want a lot of pressure...usually I just blow over the end of the pee hole or the pee hole's hose if I have it off already. That way it won't overpressurize the system, but if there's any pieces of sand or impeller in there, it'll come out of the water tube.

Also check your pee hole hose...seen a few get stopped up or restricted with sand/dirt. Usually where there is a restriction in the system, like when a hose necks down to a smaller hose connection. Tee connections. Y connections, etc.

also if the impeller cup is worn, it should be replaced as the worn spots directly above and below the impeller allow internal leakage of the water pump-which reduces it's suction and pumping ability. If any gaskets, watch those. And also watch teh water tube seal where the tube meets the pump housing-if it leaks there, it'll do exactly what you're describing.