On May 11, 12:34 pm, f499 wrote:
I need advice on spark plugs. I decided to give the Mercruiser a
minor tune-up (plugs, rotor, cap, gas filter). I removed the OEM
plugs, which are AC 41-932. Interesting find, given the plug number
on the flame arrestor is AC MR43LTS. To make things even more
interesting, I go down to my local boat shop and request six AC
41-932. The parts guy tells me that the number means nothing to him
and that he needs the serial number. The engine serial number is
OM642767. He is still confused and can't find me my AC 41-932's.
Further to more reading on the Internet, I notice that the AC 41-932's
exist (most online boat shops offer them). Although, the description
claims it's for 2001 and newer engines that are equipped with MPI
(4.3, 5.0, 5.7, 6.2). I compared the 2 different plugs and the
electrode on the 41-932 is much smaller in diameter than the 43LTS'.
The 41-932 is labeled as a platinum plug, and claims to last
100,000miles.

Here are my questions:
Which plugs should I install?
Is the 41-932 a colder plug, which helps minimize dieseling (run-on)?
Since I fog my engine each fall (winter storate), shouldn't I run
plain plugs (instead of platinum) and change more frequent?

Thanks in advance,

F499

Platinum or regular is a personal preference thing. I use regular
plugs myself.

Run-on is a bad sign and often has nothing to do with the plugs.
Often it is the result of hots spots created by detonation or carbon
build up. If you have persistent run-on I recomend running a higher
grade of gas as the first thing to try.