| Powerhead | |
| No. 2155 October, 1986 |
Subject: Engine Modifications for 86 AKI Octane Lead-Free Gasoline
Models: 1970 thru CO, 60 thru 2.6 XP/GT
Some Johnson® and Evinrude® 60 thru 2.6 XP/GT TM models, as originally manufactured, required leaded regular gasoline of a specified minimum octane rating.
If some of these Johnson and Evinrude models are operated on lead-free 86 AKI (Antiknock Index) gasoline, without being modified, extensive powerhead damage may occur.
Johnson and Evinrude models will operate, or may be modified to operate, on unleaded gasoline. Included in this bulletin is a scaled down outboard portion of Wall Chart CR85-54. The chart lists the models requiring modification, the modification kit part numbers, and part numbers of individual, low compression, cylinder head gaskets.
The modification kits contain installation instructions and a decal to identify the motor has been modified for 86 AKI lead-free gasoline.
The 86 AKI timing specifications are for original powerheads only. For replacement powerheads, refer to instructions provided with the powerhead.
In most cases, there will be a slight power loss after the engine has been modified to operate on 86 AKI gasoline. If necessary to maintain good acceleration onto plane, reprop the motor to run in the upper end of the full throttle operating range.
If the full throttle RPM drops below the recommended operating range with normal boat load, install a lower pitch propeller to prevent powerhead damage.
Encourage your customers to use good quality gasoline that does not contain alcohol. Gasoline/alcohol blends can attract water and form corrosive materials that attack fuel tanks. Alcohol may also cause deterioration of nonmetallic fuel lines. Caution customers to have the boat's fuel lines and fuel system components inspected regularly for signs of deterioration.
Do not use gasoline containing methanol (methyl alcohol). Methanol is more corrosive than ethanol (ethyl alcohol) and could cause permanent damage to fuel system components.
| CR85-55 |
