I have a Volvo 170AQ. It is an older model from the late 70's. Last week
on the lake it over heated and started making a knocking noise. I took it
home, replaced the impelller, but it idles real rough.

Anyone have any idea what could be going on.

A little more info, the boat sat for a few years prior to this trip. It
stalled a few time getting it lauched, but ran pretty good for about 5 to 10
minutes when it over heated. I inspected the oil and it looks and smells
okay.

Thanx,
Mike