Try a colder heat range plug. Are they the correct ones for the marine
motor? The carburator probably needs rejetting otherwise - just take it off
and take it to a carb shop.


"Bob" wrote in message
...
Curtis CCR wrote:
(Bob) wrote in message...

: My Volvo AQ130C 4 cyl/130 hp engine (a factory rebuild with about 85
: hours on it now) pings when I am at sea level and running above about
: 4400 rpm...not a real bad ping but a ping none the less that concerns
: me...this despite using 91 octane gas with octane booster added to it.
: It does not ping at all at on Lake Tahoe (6200') using the same
: gas/octane booster. I checked the ignition timing today while out for
: a cruise on Lake Tahoe and it was right on spec, which does not
: surprise me since the engine was installed and tuned at Lake Tahoe.
:
: My question is this...does altitude affect ignition timing? I guess
: one way to find out is to put the timing light on it next time I have
: it down at sea level.
:
: Any other ideas why it might ping at sea level?
:
:Is this a carburated or fuel-injected engine? If the engine was

Carbureted. Dual, single bbl Solex PA 44 PA1.

:"tuned" to run at 6200', the mixture may be set too lean for use at
:sea level.

When you say "tuned", is there anything I can relatively easily do to
tune it while at sea level in an attempt to stop it from pinging?

:But yes, timing too far advanced can cause detonation too. And you
:can get away with advanced timing at altitude if the mixture is too
:rich.

I checked the timing and it was essentially right on spec (27-29 BTDC @
2000 rpm) and the timing has not been touched since I got the engine in
the fall of 2002.

Replies to a post I made to boatered.com suggest that the carbs need to
be re-jetted for sea level operation. Sounds like a major job though
for a DIY'er, especially since I'm dealing with carbs that are 32 years
old.

Thanks.