-> The room fell silent as Brian Glapa whispered to John Duke/all...  
 
 BG> There we go , now we're getting into it....  I was told that the mercs 
 BG> had a reed valve system rather than the rotoray valve that the omc  
 BG> used. 
 
OMC & Merc both use reed valves. The difference is that earlier Merc's placed
the reeds around the crankshaft and OMC placed them behind the carbs. Merc's 
design created a shape similar to petals of a daisy and they suffered 
frequent breakage because of the narrow design at the base. Coupled with the 
fact that the engine had to be completely disassembled to change them made 
for a mighty expensive repair. Smaller OMC's had the same petal design, but 
since the reeds were behind the carb, repair was quicker and easier. Larger 
OMC's (50hp and up) used square reed sets and thus eliminated the inherent
week design flaw. With respect to a rotary valve, it is Rotax that uses this
innovative (and patented) design. Since Rotax is a Bombardier company, you
will see this type of arrangement on Ski-Doo's & Sea-Doo's. 
 
 BG> Now I don't know how it is on the newer models but with a reed  
 BG> valve as you crank up the rpms the valve tends to stay open  
 BG> better/longer and with a rotary valve the higher rpms tend to limit  
 BG> the time or dwell that the valve can stay open. 
 
Reeds tend to 'float' at around 8,000 RPM (depending on the design). They 
work fine up until then and thus work great on Outboards. A Rotary valve has
no such limits and can be run as high as the engine will handle. 
 
 BG> I know on my old '58  
 BG> it won't rev up very high, and my dad says that his old merc would  
 BG> scream. I think that may be another reason that the mercs were winning 
 BG> hydro races etc...    
 
Engine RPM is a factor of design first, and prop pitch second. If my engine
is designed to run 6,000 RPM and I prop it wrong, it will still not reach 
it's designed limit. Incorrect propping is the bane of this industry. You're
old 58 would scream too if you dropped the pitch down a notch or two. How
long it holds together is another matter. 
 
 BG> Does anybody know a good going price for a 50 horse merc...elec. start 
 BG> 4 cyl????  I was told for a 1960 to 1970 or so it could range from  
 BG> $500 to $800.  I'm just looking around so I don't get taken to the  
 BG> cleaners...  
 
*Any* engine in this year range would not be worth more than $400 in my 
opinion. Consider that you can slide into the seventies and get a newer more
reliable engine for the same money..... 
 
Regards, 
 
          Dave 
  
... When we shout, everybody looks. When we whisper, everybody listens. 
--- Blue Wave v2.12
---------------