Posted by Charlie on Monday, August 13, 2001 at 11:26PM :
In Reply to: Why so many good marine diesels and none for us posted by Dave on Monday, August 13, 2001 at 10:25PM :
The same basic motor (B series Cummins as na example) will usually have its' highest ratings as a marine engine. Why?
The manifolds are water cooled, intercooling can get charge air down to water temp (like 40-60 F.) no matter how high the boost, there's an infinite supply of water for direct or heat exchanger cooling, and the engine is only fully loaded at max rpm, which means relatively rarely. The application and stresses are more "controlled".
In particular: HP demand of a prop in water is proportional to the 2.5 power of the rpm. That means at 90% of full rpm is only 77% load. You can easily fully load or even overload a vehicular application engine at lower than peak rpms. That coupled with high fuel settings means real high EGTs. The only time there's any concern about EGTs in marine applications is full throttle/top speed.
Charlie
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