What Octane/Racing fuel should I use

[danamul1977]

Hay, I have a 1990 200hp merc that was used for racing back in the 90's. I was told to use racing fuel in it. It has higher compression then normal 132psi and larger jets. They prob re ringed it with steel I was told. Looking for any recommendations on what fuel to use (octane level). I was thinking maybe the 100 octane, or has anyone used those octane boosters, im not sure about them. The guy I bought it from said 93 would work if I cant find racing but racing would be better. Any Thoughts

 

[Chinewalker]

Re: What Octane/Racing fuel should I use

If your powerhead is anything like the one on this puppy, 100 would be the way to go...

 

[wired247]

Re: What Octane/Racing fuel should I use

What is your cranking compression?

 

[Faztbullet]

Re: What Octane/Racing fuel should I use

How about a picture?

 

[danamul1977]

Re: What Octane/Racing fuel should I use

That is the cranking compression so maybe its not that much higher then normal high im not sure, kinda thinking normal would be 115 or so. The main jets are .088/.086, spec is ..082/.080. Thx for any help
I should take some pictures, really just the crowl looks/has been modified with air intakes on both sides for the carbs.

 

[wired247]

Re: What Octane/Racing fuel should I use

92-93 octane will work fine on 132 ish compression as long as you dont go crazy on the spark advance. 24 degrees . No more.

 

[mr 88]

Re: What Octane/Racing fuel should I use

You could also find out where the local stock cars guy buy there race gas and buy 5 gallons.Then mix that 100-108 octane gas to get a bit higher number like 95-96.I put 1 gallon into 5 of premium. I prefer that way of bumping the numbers over buying some octane booster.As 247 noted ,time it before you punch it.

 

[danamul1977]

Re: What Octane/Racing fuel should I use

It was about 24 at cranking, so that should be fine. They're some stations that sell racing around here so when I can ill do that 5-1 mix, but its good to know I can use 93 without problems. thx guys

 

[wired247]

Re: What Octane/Racing fuel should I use

make sure you disconnect the timing module (if you are still using it) when timing the motor.