Spark Knocking Problem

[DonziDave]

Boat: 1986 18C

Engine: Merc 350, T-Bolt ign, mild HM marine cam, Edelbrock Performer intake, Q-Jet carb.

Problem: I have never used anything but 93 octane gas with no problems. After reading some recent posts stating that my engine should use 89 octane, I thought I would give it a try. At WOT it spark knocks pretty bad. Is this the gas or a timing problem? If timing, what is the correct setting?

Thanks - Dave :confused:

[MOP]

Boat: 1986 18C
Engine: Merc 350, T-Bolt ign, mild HM marine cam, Edelbrock Performer intake, Q-Jet carb.
Problem: I have never used anything but 93 octane gas with no problems. After reading some recent posts stating that my engine should use 89 octane, I thought I would give it a try. At WOT it spark knocks pretty bad. Is this the gas or a timing problem? If timing, what is the correct setting?
Thanks - Dave :confused:

Set top at 32 degrees, if you look at the pack they are marked. Should say V8 20 22 etc, example a 20 degree pack sets at 12 degrees at the bottom and should climb smoothly to 32 as you wind it up. So add what ever to the packs number to get the 32.

Phil

[BigGrizzly]

Or maybe the engine needs 93 octaine like all my boats do. If it worked well all these years why change it. If it ain't broke don't fix it. besides on a 50 gallon tank 93 octaine is onlt $6.00 more on a tank. how much is a detonated piston?

[DonziDave]

Mop - Thanks for the always precise information. When you say look at the pack, I assume you mean the T-Bolt ignition pack...yes? I would like to verify my timing.

Grizz - I agree about the 93 octane. Been running it the boat for 20 years. Why try to save a couple of bucks....!!!!

Thanks for the replys - Dave