quote:Originally posted by TheRock
On an out board 225 HP. 2 stroke engine.. what oct. fuel is recommended ? Is there any real advantage in using higher grade fuels eg. 94 oct. vers. 87 oct. on an out board 2 stroke engine ? Boat storage in winter time... will a 94 oct. fuel in your tank is less likely to go bad than a lower grade fuel say 87oct. ?
I think I answered my own question here.. find some stuff on the net on this topic....
18. I have an outboard with higher compression. Should I burn PREMIUM gas?
NO! Here's why. The octane ratings are composed of 2 components, research octane and motor octane (RXM/2) divided by 2. The RESEARCH octane is the quality of the base stock, the MOTOR octane is derived from additives. The oil company will never tell you the ratios. Problem is the highest octanes are achieved by MOTOR octane additives, which will just gum up the pistons in a 2 cycle engine. Base stock is generally the same. The MID-GRADE gas has the detergent additives needed to clean your motor and sufficient octane for MOST motors. If you have a MERCURY, FORCE or OMC motor from the early 70's thru mid-80's refer to technical bulletins from the manufacturers for timing changes and replacement head gaskets to lower compression to use today's gasoline's.
from an online forum..........stick with Regular, premium burns to hot for the engine and shortens the life span, burns out the rings in the system as well.. its a major no no.. if it pings, take it to a dealer.. let them sort it out.. dont shorten the life by using the wrong fuel, even my local yamaha dealer said.. "Yamaha outboards are made for standard unleaded fuel because its easier to get and that is what they are designed for"
-----OrigYes, this is and old topic that pokes its head up every now and then. Premium does burn hotter in the combustion chamber and that is largely anaffected by the general engine temperature that is mainatined by water flowing through the engine. Premium is more designed for high performance engines and can cause damage to the pistons, valves and rings of engines not designed for premium if used for an extended period. Pinging will also damage an engine and this should be sorted out either by the seller if still under warranty or by a suitably qualified technician. The only engine I know that would be designed for premium would be the Mercury Verado range of supercharged 4-stroke outboards.