Propeller problem?

[steelespike]

If the 22 gave you 4800; a 23" would usually lower rpm about 200 and top speed probably would be about the same as the 22" prop with slower hole shot.
Comparing the 4 blade 21 to the 22 would likely be slower.Hole shot should improve along with the other improvements i have suggested for a 4 blade.
I think you should forget about a prop until you get the bottom smoothed out and measured to see if there is a hook.
For now I would stick with the 22.

 

[kallewell]

Your description seems to indicate a hull problem.If it has trim tabs release them all the way.
The hull may have a hook in the bottom near the transom.Lay a straight edge along either side of the keel. Bottom should be straight.

So you mean I need to check that first? But IF the hull have a hook, it isn't possible to fix it?

 

[steelespike]

The 22 Seems perfect for now.No sense buying a prop when you won't now if you really need one
until you know you have a good bottom.
It is possible to repair a hook. It depends on the cause and how severe.
If its a general hull failure it can be really involved having to take the floor out and replace the framing.
If it's just slight problem Its possible you could simply fill the depression with something like a fiber glass product.
That's assuming it's structurally sound.
Just getting rid of the paint problem could add a couple of mph.
It's not unusual for a boat to slow slightly simply from painting the original bottom.

 

[kallewell]

New season and new chances
I have now totally cleaned the bottom of the boat, installed complete MSD ignition, ad tried a new propell.
Three blades steel prop 14x23.
With this it reached 53 mph, but only 4150 rpm..

What to do next? Try a four blade 14x21 to try and lift the boats nose?

 

[kallewell]

Does anybody have any suggestions..?