repowering, proper prop sizing?

[wantokex]

I have been offered a good price on a 6 cyl 120 hp Lehman diesel motor to replace my 4 cyl 80 hp Lehman for my newly purchased mess of a 72 gulfstar 36 motor sailer. what is the proper way to figure out the right prop size and pitch for the motor?

Wantok

[cockeyedbob]

wantokex
same delema last winter ... did the research, crunched the numbers, and submitted boat and engine specs to everyone I could think of and when the results came in, most agreed on the same dia and pitch ... bought one so after launching we'll see ... other than that, I haven't a clue ...

[wantokex]

After crunching the numbers myself, I am going to go with a straight replacement instead of a upgrade to the 120 hp, the cost to re-work the engine bed and a lot of other stuff was to steep. now I just have to find a rebuilt motor for a good price. Best so far was from bomacmarine.com @$8000 for motor and $2500 install costs very friendly guys.

Wantok

[cockeyedbob]

... a good plan ...

for bob's project, prop, shaft, seals, bearings, trans and new 55hp diesel ran 11,300 ... bob's labor ... 'course, put in perspective, got less than 12,000 in a welded, primed, ballasted 37' steel hull ... 'taint cheap ... everyday I think a 28 footer would have been just dandy

good luck mate ...