what should the initial ignition timing as well as the advanced timing be for a carburated hp 500 and at what rpm

Set the timing at 34 degrees at 3500 rpm. What ever the initial is, when you have the maximum set, is fine (it doesn't matter much). 35-36 would probably give you a little more power, just make sure that you run premium fuel if you do.
Dennis Moore
www.mooreperformance.org

thanks guys

Dennis,
I read in my Merc manual that the HP500 (carb) advance curve is not all in until 4500 rpm. Theoretically, if you set the initial at 14 degrees, it should max out at 34 degrees @4500. Perhaps the 4500 rpm is a misprint in the manual. But if it isn't, and you were to set it to 34 degrees @3500 rpm as you suggest, the total advance would be more than 34 once you exceed 3500 rpm. Which is correct?

Also, I have a queston about setting the idle speed once the timing is adjusted and the distributor lead is still grounded. On my HP500s (1999's), when the wire is grounded and the base timing set to 14 degrees the motors idle around 1000 rpm. Once you disconnect the ground wire the idle drops to 700 rpm as the timing retards several degrees. I understand that the T-Bolt V ignition is designed to keep the idle speed at 700 rpm when you put the drive in gear, so it must do this by altering the timing.

But, oftentimes after cruising and slowing to idle speed, if you put the drives in neutral the motors idle at 1000 rpm and won't slow down to 700 rpm for a minute or so. This is annoying. I noticed by coincidence that if you hit the drive trim switch while the motors are idling fast, they will then drop back to 700 rpm, but not always. So my question is, with the distributor wire grounded, should I lower the idle speed to around 800 rpm by turning the idle screw on the carb? Will this leave enough of a window for the T-Bolt V to work with as far as controlling the idle rpm in gear?

Thanks for your input.

Rich