Mercruiser 120 best prop for skiing and tubing

[Tbandit07]

Needing some help picking a new prop out. I have an 82 citation sprint. It's about 16 1/2 feet long with a mercruiser 120. I dont know the current prop info besides it's really chipped up and is a 3 blade. Currently at wot I'm around 3500-3700rpms depending on people in the boat and it's at around 20-22mph. I pull tubes fine but I wanna pull skiers as well and want to have a little more speed when I pull the tubes as well. Any recommendations on a prop size and type. I'm currently leaning towards a spitfire 4 blade 15 pitch but dont really know enough yet to pull the trigger. Any and all help is appreciated.

 

[Scott Danforth]

your WOT is low.

a 3 blade 15P is what I would start with.

max speed for a tube is 25. skiing you want 30.

120 hp is on the low side of power for watersports

 

[jimmbo]

Is the engine in good mechanical shape, and in a good state of tune? Is the hull clean and smooth? Reducing the dead weight in the boat, no extra passengers other than the spotter just might allow you to pull a skier

 

[Tbandit07]

The engine is running fine but is old. The hull is pretty damn dirty and is getting scrubbed down before this weekend. I ment to do it before but ran out of time. The boat sat in the lake all last summer so she got really dirty and the previous owner did not clean her when they took it out. Do you think my boat would struggle to turn a 4 blade 15p prop like the spitfire?

 

[Sea Rider]

To take the max HP out of a underpowered engine, hull must be impeccable smooth clean, engine revving to it's full max wot rpm range with just driver, spotter and skier. The rest can stay at terra firme zipping cold ones. Less pitch 3 blade props will do the trick,

On a theoretical point of view won't know if going for a 4 blade 15 pitch will do its homework right, need to test it on practice with a wot spin on flat calm water cond and fine tune a prop from there if not suited for your boating needs.

Happy Boating

 

[jimmbo]

I will assume the boat is fiberglass. If it sat in the water all season, the hull will have a build up that will slow its acceleration and lower its top speed. You will probably have to resort to serious chemical cleaning(muriatic acid) to get the growth off. Commercial Toilet Bowl cleaner works pretty good, as it mainly is the same stuff.