Are my calculations in line.....

[staydry]

[FONT=&quot]Looking to size a prop for a 25HP inboard @ 3600 rpm...there are numerous sites out there for performing the calculations but this one appears to request the pertinent info ........... VICTORIA PROPELLERS[/FONT]

[FONT=&quot]Based on the requested criteria...they suggest a 11.1" x 7" 3 blade prop[/FONT]


Is this in line with the operating specs listed??? Thanks

[FONT=&quot]WL 17.5' x 5.5'[/FONT]
[FONT=&quot]Displacement type hull..... 1,900 lbs[/FONT]
[FONT=&quot]Gearing 1.45:1[/FONT]
[FONT=&quot]Draft 5"[/FONT]
[FONT=&quot]Speed 10 Knots[/FONT]

 

[Sea Rider]

Which was the max wot rpm achieved as usually loaded with current prop to know if at least middle to max wot rpm range factory stated for that engine ?

Happy Boating

 

[staydry]

Should've mentioned that I am building this boat which was designed in 1938....engines he recommended are no longer available...have been discussing with Beta Marine they see no reason for a 90 CI gas since the same output can be obtained with today's current engines with less CI due to the wide assortment of gearing that is available.

The following is an excerpt from the designer....

 

[ondarvr]

It say's 90 cubic inches, not HP

 

[staydry]

It say's 90 cubic inches, not HP

Fixed...don't know what I was thinking...thanks

 

[Sea Rider]

So it's a 90 cubic inch motor with max 2000 wot rpm, right ? If conversion table is right, that's 1,474 cubic centimeters. Definitely not a small engine. What type of prop is needed, non through hub old style or through hub newer style so to play with prop pitches ?

Whichever prop you go after must be water tested with an induction tach at wot as currently loaded to check max wot rpm achieved for engine to work on the relax side, which is a must.

Happy Boating