Prop choice mistake

[valvebounce]

I recently changed my prop from a 9.25 X 11 to a 9 X9 because my boat was having trouble getting out of the hole.The result was instant,the boat jumped up on the plane with no problems.
I had changed the coils and HT leads,points etc.
I then realised I had run the HT cables to the plugs the incorrect way,which restricted the accelerator plate under the flywheel,this caused a restriction on the plate and the engine wasn't reaching it's full WOT.
I re-ran the HT leads and the boat reached WOT no problems.
I now realise that the 9 X9 prop is causing me to use a lot more fuel,and the top speed is well below it's potential.
I am now going back to the 9.25 X 11 prop which should give me better fuel economy,plus a higher top speed.
A costly experience,I paid 125 GB pounds for the 9 X 9 prop.
The outboard is a 1963 18hp Evinrude twin,a great old war horse.

 

[jimmbo]

It would be nice to know what RPMs the engine is turning

 

[valvebounce]

It will rev to 5000rpm,the Wot is 4500.
I am not in it for speed,I use the boat for sea fishing.Getting on the plane and maintaining a constant economical speed,with that extra bit of power for tricky situations is my aim.The 9 X 9 prop was causing me to use a lot of fuel.

 

[Chris1956]

Well, you now have a spare prop. Not a bad think to have.

A prop shop may be able to repitch it to 10" or maybe more.

 

[Scott Danforth]

The lower pitch prop will make a good spare, and when you have lots of load.

 

[valvebounce]

A prop shop in London changed this prop from new,from 9 X 10 to 9 X 9.
Like you guys say,it will make a good spare,or will be useful for heavy loads.

 

[jimmbo]

The engine is rated @ 4500 rpm. the WOT range is 4000 - 5000 rpm