The original prop should have a mark somewhere on it telling you what size it is.
If it's an aftermarket Michigan then it will have a series of #s and letters.
Post what you find.
The 19 Bayliner with a 125 can run anywhere from 35-45 mph.
Do a compression test, then unload all the extra stuff on board and go for a ride.
Most people(me too) carry to much extra crap and it all adds up to slow you down.
Run it 2-3 time at wide open making sure the motors trimmed right.
Post the results along with the prop numbers or size.
Pretty sure you probably have a 19p maybe a 17p stock prop.