Range its all about efficiency

[Barry]

These calcs are a bit silly. First you calc the rpm at the prop and what diameter prop that engine can swing.

If you are referring to my calculations, I never mentioned prop diameter.

 

[whitepointer23]

gph is a bit silly. mpg is much more useful to most people .

 

[FAST FRED]

"A 2 speed boat. Fast locally, slow to cross oceans. "

You have answered your own question, a 2 speed transmission.

By speeding up the prop at low engine speeds you can get back in the "bulseye" on a BMEP graph.

ZF makes the tranny , but obtaining a BMEP graph from an engine source is almost impossible for small engines.

Perhaps claiming your company is a pump builder or genset Mfg might spring one loose.

 

[mydauphin]

"Range its all about efficiency" has a lot to do with the boat too.

A variable pitch can also make a difference, acts like a variable speed transmission.

gph, mpg are all not real... most boats gpm. Most boat never get below 1