Overheating problem

"I have a 1971 mercruiser 165.

"I have a 1971 mercruiser 165.Last year I replaced my impeller and found that most of the fins were broken off.I removed the bottom of the unit and flushed it out from both ends and believed i got all of the rubber out.The engine runs fine at 2000rpm but starts to creep up any faster than that.Was wondering if there were more pieces still in there.Iwas wondering if when you put a hose to the intake hose, should there be any pressure or should water freely flow to the engine without restriction.This is driving me nuts! thanks."

"You should check your T's

"You should check your T'stat first to make sure it is not frozen in a part open position. If in doubt at all, change it.
The next thing I would do is drop your lower gear unit, and backflush the whole water inlet line from the connection at the T'stat housing with a garden hose. This will tell you if you are getting good flow to the engine. If it seems restricted, you likely have more impeller bits lodged somewhere and you will have to start taking things apart and flushing them individually. Any impeller bits that made it into the engine are likely settled in quiet places in the block water jacket and will not do any harm.
It's also possible that your water inlet hose between the outdrive and the transom assembly is kinked, or the inside hose from the transom assembly to the PS cooler may be kinked. Check these carefully, particularly if the backflush water flow seems restricted at all. Your engine needs about 20 GPM of cooling water, so it must flow freely.
Rod"