I recently picked up a 35 Lightening with 2 500 EFI. It is really hard to find anything higher in octane than 93. What does everyone else run?

You are wasting your money putting anything over 87 in it:

HP500 EFI specifications


[ATTACH=CONFIG]544900[/ATTACH]



HP: 500
kW: 390

Full Throttle RPM Range: 4800-5200

Displacement Liter/CID: 8.2/502

Bore & Stroke (in): 4.47 x 4.00
Bore & Stroke (mm): 114 x 102

Compression Ratio: 8.75:1

Cylinder/Configuration: V-8

Alternator Amp: 60
Alternator Watt: 847
Fuel System: MPI

Ignition System: Digital

Fuel Requirements: 87 Posted Octane (R+M)/2 (92 RON) International

Transmission: (Six) w/Huber 600 Series

Drive Unit: Bravo One XR, Bravo One XR w/ITS, Bravo One XR Sport Master (Standard or Short), and Bravo One XR Sport Master (Standard or Short) w/ITS. Dry-Sump Six w/Huber 600

Drive/Gear Ratios: Bravo One XR/Bravo One XR Sport Master - 1.26/1.35/1.5:1

Length (in/mm): 39/991
Width (in/mm): 34/857
Height (in/mm): 22/560
Weight (lbs / kg): 1113/505

Warranty: 1-Year Ltd. for Recreational Boating/3-Year Ltd. Corrosion

CARB Star Rating: 3

Features & Benefits
Precision CNC machined 502 C.I.D. cast iron cylinder block.
Forged 4340 steel, fully machined and shot-peened Mercury Racing connecting rods.
Forged aluminum pistons, designed by Mercury Racing, for maximum strength and durability.
MEFI 3 Electronic Control Module digital ignition system features advanced electronics for more precise fuel and spark control along with better top-end throttle response.
Multiport fuel injection system incorporates a high-flow throttle body and tuned intake manifold developed exclusively by Mercury Racing.
A thermostatically-controlled, high-capacity oil cooler raises engine oil temperatures faster and keeps them more consistent.
The oil thermostat and a Positive Crankcase Ventilation (PCV) valve work together to reduce the buildup of condensation in the oil. The PCV valve also improves engine idle.
A hydraulic roller camshaft, which improves low-end torque, offers higher level of performance and aids fuel economy.
A one-piece serpentine belt system requires less horsepower to drive engine accessories.
Comes standard with 1.26:1, 1.35: or 1.50:1 gear ratio Bravo One XR drive in either right-hand or left-hand rotation.
Dual-water pickup and low-water pickup gearcase housings available for standard Bravo One XR drives.
Bravo One XR Sport Master, Bravo One XR Short Sport Master and Dry-Sump Six drive options available.
The Bravo One XR Sport Master gearcase (Std. and Short), available on selected Bravo One XR drives, reduces drag for enhanced overall boat performance in select applications.
Integrated Transom System (ITS) available with Bravo One XR and Bravo One XR Sport Master drive options.
New engine oil drain line enhances ease of changing oil.

All you need is 89 octane. Don't bother with anything over 93, your ECM map isnt set up for it.

They actually run bad on anything over 87

If they're stock then Mercury recommends 87. I run 87 in mine and have no issues. Unless you've bumped the compression up or have SC it, I see no reason to run higher than 87 octane.

87, they're not even 9:1