Overheating at mid range 225 carb 1996

"I'm stumped. I'll try

"I'm stumped. I'll try to hit the facts: All started after dropping the lower unit to repalce a shift shaft seal. Changed the water pump also.
Temp at idle is fine. Between 3,400 - 4,000 rpm, engine temp will slowly climb to 1/2 then 3/4, then alarm. Drop to idle then comes down to 1/4.
Yesterday just befor temp hit 3/4, I opened it up to max 5,500 rpm and temp dropped from 3/4 down just above 1/2. I have changed water pump again. Inspected water pickup gromet.. good. Checked P/Valve.. looks fine. Took thermo's out and flushed down. Put hose on remote flush tube, heavy flow out of thermo outlets. Temp on this motor never ran over 1/2. ??? Thanks.."

"sounds to me there is some so

"sounds to me there is some sort of blockage or warn impeller, when using the garden hose cold water is forced into the the gear housing and past the impeller, to the water pump... at the lake the impeller has to pull the water from the lake and push it to the water pump, i am having the same issue with a new impeller that i just retardedly burnt up today. i turned the water on, jumped in the boat, fired it up, adjusted shift cables, looked to see if the prop was spinning and noticed no water coming out. shut off motor, jumped out to find the garden hose laying on the ground under the boat. Worried that i burnt the impeller i hooked up the water and let it run for about 30 minutes and it never went over 1/4, but at the lake today it was creaping twards 7/8.
So i am betting on the impeller in your case as well.
good luck: Jeremy."

"Thanks Jeremy.. I was not cle

"Thanks Jeremy.. I was not clear on my motor. It's a Mariner 225 Carb Outboard. I am going to check the impeller, key-way, and pickup tube. Tx"