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

check your riser in the exhaust its probly cloug solid and you will
overheatyhey have to be cleaned or changed!! good
luck

"news.redshift.com" wrote in message
...
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.

If the rough idle just started happening, then I would expect that the
overheating damaged something. A likely possibility is a blown head gasket
(not too hard to fix) or a warpped/cracked head (major bummer).

First step would be to buy/borrow a compression tester. To use this you
remove all the spark plugs and thread the tester into each spark plug hole,
one at at time. Crank the engine with the starter a few revolutions and the
tester will indicate the maximum cylinder pressure. You should see
pressures in the 110 to 140 PSI range, and what is critical is that all
8(6/4) cylinders be roughly the same. A range of 120 to 130 would be fine,
but ff you get one cylinder at 40PSI while all the others are at 120 then
you know you have a problem.

If compression checks out okay, then I would try a standard tune up, and
then I might try just using it. If the rough idle is an indication of a
more serious problem then actually running might make it obvious.

Rod

When it overheated two valve guides got to hot and wouldn't let the valves
slide, so I was running on 4 pistons.


"news.redshift.com" wrote in message
...
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