It is critical that the fuel and oil requirements for the various Indmar/Ford based engines are followed.
The standard model 360 and the premium 400 and 440 (Malibu 410 and 450) models are designed to operate on 89 octane fuel with a maximum ethanol content of 10%.
The new model 460 and the supercharged 575 are designed to run on premium grade,
91-93 octane fuel with a maximum of 10% ethanol.
All of the 6.2L Indmar/Ford engines are equipped with knock sensors that will detect pre-ignition and detonation to help protect the engine from damage if the fuel quality is low and the engine starts ”pinging” or “spark knocking”. Unfortunately, there is a limit to how much protection the system can provide. Typically the system responds to spark knock by retarding the ignition timing. In most cases, retarding the timing by a few degrees will stop the knock and protect the engine. There are situations where the system has retarded the ignition timing to the maximum allowable limit and the knock continues. This most often occurs in situations where the boat is heavily loaded, is over propped so the engine is unable to turn in its designated RPM range, and the fuel is not the required octane level for the engine. The result of operating the engine in those “continuous knock” conditions is generally catastrophic engine failure that is not covered by Indmar’s limited warranty.
The Indmar branded 5W30 and 15W50 are recommended and meet all of our requirements but any commercially available oils meeting the engine’s requirements are acceptable.
The use of an oil that does not meet Indmar’s viscosity and API requirements and a lubrication related engine failure occurs, that failure may not be warrantable.