Motor Running Rough...Ideas?
If you have a loose wire on the back of the tach, or on the battery, the tach will give you false rpms.
You can usually tell the difference just by listening to your motor, when you floor it (wot) if the hub is spun, its sounds similar to your car being in neutral and hitting the gas.
If your tach is reading incorrectly, the motor sounds normal, but the rpms may be way up.
high rpm's at half throttle... does that mean you're not able to achieve your usual speed as well?
Drain the oil and look for metal shavings.... If something let loose you should see signs of it in your oil.
One more thought, you mentioned that you went up in pitch from a 17 to a 19 which should lower your RPM. Was the diameter of the prop the same?
Also, you went up in pitch by putting on your buddies prop, so if anything your rpm's should have went down.
Generally speaking, increasing your pitch should lower your rpm by 200 to 300 rpm per inch of pitch. Since you went from a 17 pitch to a 19, you should have lowered your rpm by 400 to 600 rpm.
Since it went the other way, sounds like a spun hub....
sounds like that is your problem... can get another insert and you should be good
there is a rubber insert that effectively does what a shear pin used to do