Maramu prop size


jjjk12s@...
 

Would anyone happen to know if a 22" diameter propeller can be fitted on a Maramu?


I have re-engined with a Yanmar 75HP (3200 RPM) with a 1:2.75 ratio transmission. The theoretical optimum propeller is 22" diameter by 14" pitch.


I think the original propeller was 20" diameter. If that is the maximum then the recommended prop is 20" by 18" pitch which would not be as efficient as a 22x14. I have a previous prop that was 19" diameter but that was put on with a Perkins M60 which is very high revving to achieve the 60HP and I think the previous owner replaced it with a larger one (20x14 I think) which I have not had the chance to check the stamp on.


The boat is in a marina with murky water, box jellyfish and possible crocodiles (!) so I don't fancy diving under to measure it. The prop tip clearance should be a minimum of 15% of prop diameter.


Thanks for any help.


John 

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