prop shopping but no real clue other than a suggested 19p

[skinny1965]

48 78124 a40 23p that is the current prop on my 16.5 fibreglass sea hawk with a 120 merc
currently the boat is a dog out of the hole as a matter of fact it might not get on plane and you start again I would not try to pull a skier or tuber
I have had a 17p offered to me but not sure on what dia nor if it will be to small
I have not watched the tach very much as most of the time I have been out I have had lots of other stuff to deal with since the boat is new to me

any pointers would be great

 

[SkiDad]

if the 17p is free try it to get your RPM, but it might overrev (anything over 4800) if not free, pick up a 19p - it will likely be good enough. There should be tons of these props b/c the 120 merc is a popular I/O

 

[steelespike]

Is this a outboard or an I/O? Remind us of the prop size,year of the motor and get us the wot rpm and gps speed lightly loaded.

 

[Starcraft5834]

What Spike said Skinny... need to know how your motor is currently performing with your current prop.. TAC rpm's your reaching at WOT.. once we have that... best advice can be offered.. we understand your current prop likely has to much pitch.. get your numbers and report back,, otherwise you'd get mostly guesses..

 

[skinny1965]

Ok it's an inboard Merc 120 Not sure tach is even close it seems to jump lots As for mph think I had it doing 30 I'm hoping to find something I can try by weekend And get better base It's so bad I'm not a fan of going out right now as it's such a bear to get on plane

 

[skinny1965]

Can you tell dia of prop from part # on it I'm at work and can't measure it

 

[jestor68]

Your 2.5L motor's rpm range is 4200-4600 rpm(1983 and later). Pre 1983 is 4000-4600 rpm.

A 14-1/2 X 19 pitch would be a good place to start.

 

[Starcraft5834]

Frankly, if your offered a 17p prop, if it's in the 14 inch range, toss it on and run it.. it's probably an improvement. 23p is way to much prop for a 120 17ft fiberglass boat. have to beleive you'd be in the ball park for rmps with a 17

 

[Gregkilpatrick]

i had a i/0 18 ft thunder craft with a 120 mercruiser and had the 19 pitch prop on it and it ran excellent at 4800 wot it would do 36 miles an hour and pull skiers and tubers all day and still be fairly fuel efficient