Tiny might propeller slip

[kens]

Slip is a difficult thing to figure out, but generally about 10-20%. I say generally because you can have a steep pitch prop and it runs with more slip than a flatter pitch prop and yet the boat goes the same speed.
My experience is that as pitch goes up, slip goes up too.
So don't get hung up worrying about slip.
With the info you have given so far, you are over-revving the engine, correct?
Then you need more pitch and/or more cupping.
Don't worry about slip,

[JhlFin]

Yes, engine over revs. 10-20% slip sounds reasonable, my prop slips way too much right now. I would be happy with 30-40% slip. I cant wait to get prop back from shop and testdrive.

[JhlFin]

Well, it took longer than it should, but finally got to test drive. There is something wrong with carb, wont idle. Carb is clean and every orfice is open, i think i will swap better/bigger carb.

Propeller is now 10x15 with cup and 5 degrees rake, much better! I ran out of power engine only revved 3100rpm and 30mph, so 32% slip. I like it, now i just need more power.

Cam and 2 barrel carburetor is next thing to try and i think i had ingition bit off.

Edit: Other gps app recorded 38.8mph, so 14% slip. It did feel faster than 30mph, so i hope its right

[kens]

That sounds like really good news.
If the GPS says 38mph, then I would likely believe it, especially since you got the engine fully loaded up.
BTW if you getting low RPM with your prop, the easiest (cheapest) way to get more RPM would be to relieve some cupping.
Cupping is the easiest thing to massage on a prop, and it has a big effect on RPM.

[JhlFin]

I went for a ride yesterday, now with fully working gps. 40mph/3200rpm so slip would be 12% Im really happy! Im thinking of upgradin engine next winter so maybe i keep prop as is for now.

I got to say boating is fun!