1992 5.0LX timing

[Wxguru]

Good afternoon everyone,
1992 Crownline 196BR with the 5.0LX V8 with Thunderbolt IV ignition system.

I recently replaced the Cap/Rotor, plugs, wires. Overall she runs pretty darn good....has 331hrs on it now (I bought it with 324.5hrs).
This past Thursday evening before Labor Day weekend, I grabbed a timing light and checked the timing at idle (temp was up to operating temp and idling about 700-750rpm).
I got a consistent 4 degrees BTDC. I know these engines are spec'd at 8 degrees BTDC. I didn't happen to have a wrench with me to loosen the distributor clamp bolt and adjust timing so just left it and we went on out to the lake this weekend.

Had a few hard starts while out on the water, and after one particularly long/hard run...about 20 minutes or so pulling a tube and then running 35mph+ for a few miles, when I turned the ignition off, she started to diesel a little bit. I immediately turned the key to the on position and let it idle for about 1 minute then off, and didn't have that issue again. Temp gauge stays a consistent 170-172 no matter the rpm (had it as high as 4000rpm).

Question is....does the occasion hard start and dieseling issue have anything to do with the timing?

I am running 91 Octane (no ethanol) and running Quicksilver fuel treatment.

Thanks!

 

[alldodge]

Question is....does the occasion hard start and dieseling issue have anything to do with the timing?

I am running 91 Octane (no ethanol) and running Quicksilver fuel treatment.

Yes sort of.
Running with less advance and 91 octane (require 87) can cause a build up of extra carbon and by products. The 91 octane does not burn as fast as 87. Add that to not having the same amount of time to burn it with less advance, so incomplete combustion of all gas.

Now add to the above items another of idle is a bit high id its above 700, spec 650-700 and lower then 700 is best if it will idle smooth without issues. That said if your tach is accurate.


Use 87, set correct timing and lower idle

 

[Wxguru]

Use 87, set correct timing and lower idle

Thanks for the help alldodge. Only reason for running the 91 Octane is that is the lowest rating that is non-ethanol, and having only had this boat since June, wanted to try to clear out older fuel (boat only ran 3 times by previous owner LAST season, and when I bought had half a tank of fuel...so about 19 gallons) with good quality fresh fuel.

I will fill it up this next go around with 87 and HEET and lower the idle a bit and re-check the timing then make adjustments and see what I get.
Just overly paranoid about off-season/separation of fuel I guess with non-ethanol.

 

[alldodge]

You may be fine with 91 once the timing and idle is set, the slight power loss and as may not be a large issue, but right now there are to many things which build on one another