Is my prop alright?

[muchy_]

After much research and general messing around I have found that the reason my engine will only reach 2500rpm must be the prop as it reaches 4000rpm out of gear (not that I rev it to that extent unloaded). Now, someone has told me that my engine produces max power at 3800rpm. Is the pitch on the prop to much? Am I better off changing the prop for a smaller pitch? Will a smaller pitch allow the engine to produce full power and hense give me more speed?
Questions, Questions, Questions

 

[Guest]

Tell us, what boat, engine hp,etc, then we might give some help..

Paul js.

 

[coliholic]

See from your profile that it's a BMC 1500, so guess it's a displacement boat used on the river or Broads?

Well I had a BMC 1800 in a Freeman 27 and that would only ever get to about the same as yours 2,200-2,500 rpm. No point in revving it higher anyway, the boat'll have reached it's maximum hull speed and to get it to go any faster it''ll need to get on the plane and for that you'll need an awful lot more power than you've got.

So about right. IMHO of course

 

[hlb]

Tell us more about the engines and boat. As Coliholic says.
So what is the hp of the engines. And wot is the size of the boat. Very important IMHO.

No one can force me to come here-----------
----- I'm a Volunteer!!!

Haydn

 

[brianrunyard]

There are links to a couple of Prop calculation progs, on my site.
You'll require;-
Waterline length, Displacement, Max RPM, hp@max RPM, Gearbox ratio, type of hull.
Hope this is of some help.

Brian
http://homepage.ntlworld.com/brunyard

 

[muchy_]

The boat is 30ft in lenght (make unkown) and has a displacement hull. The engine is a BMC1500 producing 38hp@3800rpm.
I'm not looking for dramatic improvements in performance but a little would be nice, however what concerns me more is would it benefit the engine any to be able to reach the rpm at which it produces maximum power or is it better to leave it revving up to 2500rpm where it is probably only producing around 20hp and trying to turn a higher pitched prop. If the hull reached its maximum speed when the engine was at say 3500rpm would that be kinder to the engine?