"Hi all this is going to be fa
"Hi all this is going to be fairly long winded so please bear with me.
I have a 2001 model 4.3 litre mercruiser with TBI in a Haines Signature Bowrider, I have had this boat for about 9 months. The engine is a long motor quicksilver rebuild with new just about everything being new except starter motor and alternater. When I took ownership the dealers mechanic told me to run the boat on Premium unleaded as that is what they recommend all customers to run in their mercruiser engines. I took this as gospel until I stumbled across this website and saw posts that said mercruisers are designed to run standard unleaded 87 octane. So trying to save a few bucks I decided to give it a go. No immediate differences were noticed as I was just topping up on a half full tank. I must also add that before I tried the 87 octane their was sometimes the occasional pinging or knocking that would come from the engine when under extreme load e.g pulling up a skier or when WOT around 4500 rpm.
After the addition of standard unleaded the pinging was no worse than before. So after a couple of months of good running and really no pinging, the engine decided to start to ping a little. After a bit of research on the net about pinging, came up with a few possible causes. Timing too advance, low octane fuel and carbon deposits in the cylinders. The first two looked pretty easy to deal with. Retarded the timing till pinging went but the boat lacked lot of power and would only WOT to abot 3500 rpm. HAve now drained the fuel tank in preparation to put premium into the tank. The other thing that was observed at the time of pinging was the tacho would be really erratic and even if there was a small ping you could see the tacho jump. Am I going down the wrong path of timing or octane problems or do I have some sort of electrical problem. I just can't understand how pinging would affect the tacho. Thanks to all with your replies. By the way even when the timing was retarded it did not take away the pinging.
Cheers guys and gals"
"Hi all this is going to be fairly long winded so please bear with me.
I have a 2001 model 4.3 litre mercruiser with TBI in a Haines Signature Bowrider, I have had this boat for about 9 months. The engine is a long motor quicksilver rebuild with new just about everything being new except starter motor and alternater. When I took ownership the dealers mechanic told me to run the boat on Premium unleaded as that is what they recommend all customers to run in their mercruiser engines. I took this as gospel until I stumbled across this website and saw posts that said mercruisers are designed to run standard unleaded 87 octane. So trying to save a few bucks I decided to give it a go. No immediate differences were noticed as I was just topping up on a half full tank. I must also add that before I tried the 87 octane their was sometimes the occasional pinging or knocking that would come from the engine when under extreme load e.g pulling up a skier or when WOT around 4500 rpm.
After the addition of standard unleaded the pinging was no worse than before. So after a couple of months of good running and really no pinging, the engine decided to start to ping a little. After a bit of research on the net about pinging, came up with a few possible causes. Timing too advance, low octane fuel and carbon deposits in the cylinders. The first two looked pretty easy to deal with. Retarded the timing till pinging went but the boat lacked lot of power and would only WOT to abot 3500 rpm. HAve now drained the fuel tank in preparation to put premium into the tank. The other thing that was observed at the time of pinging was the tacho would be really erratic and even if there was a small ping you could see the tacho jump. Am I going down the wrong path of timing or octane problems or do I have some sort of electrical problem. I just can't understand how pinging would affect the tacho. Thanks to all with your replies. By the way even when the timing was retarded it did not take away the pinging.
Cheers guys and gals"