[C38] Universal M30/5424 reduction ratio -- Prop size

[Max soto]

Jon, the HBW 100 is suppossed to be 2:1,  and thats what the tags says, but as a fact, that right ratio is 1.8:1. Several C38 owners found that out when they ordered a new prop with the 2:1 ratio, and the prop turned out to be over pitched, so, after careful measuring, they found out the discrepancy..  This is not only C38 related. Every HBW 100 that says 2:1 is in fact 1.8:1..
I did a rebuilt on my tranny, and just curiosity, I checked it and is 1.8:1..

Hope this helps..


Max Soto A.
C38 #198 Estancia
+506-8312-1367
Alajuela, Costa Rica

On Jun 4, 2013, at 8:12 PM, Jon Whitney <jonwhit23 at aol.com> wrote:

> Hi All,
> I was just researching the proper prop size and pitch to match the Universal M30/5424 on our Cat38's (as I'm sure many of you have done).  I just got off the phone with Catalina Direct and we stumbled upon an interesting question that you may know the answer to.  We were looking up the gear reduction ratio on the transmission for the original M30/5424  and found a discrepancy in the ratios reported by Catalina and Universal.
> 
> The Universal Maintenance Manual for models 5411/5416/5424/5432 states that the transmission reduction ratio is 2.14:1  (with an HBW-10 Hurth Transmission) on the 5424 (24 hp, 3 cylinder, 2800 max rpm).  However the Catalina factory specs state that the gear reduction ratio is 2:1 (for the same engine).   Does anyone know which is accurate and why the discrepancy?
> 
> The difference doesn't seem like much, but when they punched all the numbers to determine ideal prop size it changes the pitch ~ 1 inch.  E.g., using the 2-blade fixed prop a ratio of 2:1 gives 15" x 13" pitch (13.3" to be exact), whereas the ratio of 2.14:1 gives 15" x 14".
> 
> From what I could gather the older S&S C38's with the Universal M30/5424 came standard with a 2-blade 15"x13" and an optional 3-blade 15"x12". Obviously, the 15"x13" is fine as thats probably what most of us have had, but just wondering which ratio/pitch is more accurate and if anyone has used the larger (15"x14") prop size. As always, I'm grateful for any advice.
> 
> Best,
> 
> Jon Whitney
> 1979 Hull #54
> "Eye Whitness"
> Honolulu, Hawaii
> 
> ps. Thanks to everyone for their comments on thru-hulls sizes (especially Max, Les, and Steve).
> 
> 
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