Z260 hydra sport 120 looper 6,200 rpm

[Ryan hall]

First post here been reading the wealth of information for a while. So, my boats prop is stamped 13 3/4 x 13. 1993 120 rude looper, according to my tach ( of course it could be wrong) cranking 6,200 at wot. Seems a bit much to me. The boat only weighs 850 dry without the motor. Like to have the rpm around 5,800. Any suggestions? Hole shot is amazing right now but figure i may be able to gain a little top speed and not sacrifice much low end due to boat weight if i go up in pitch. Also may be able to keep the motor together a little longer. Hahaha
six inch jack plate and hydrafoil on the engine already. Thanks

 

[NYBo]

Welcome to iBoats! :welcome:

If the tach reading is correct , you are under-propped. A 17" pitch prop would be a good starting point.

 

[Ryan hall]

Thanks for the reply, forgive me if im ignorant of the technicals but i thought (from reading) that for every 1 degree in pitch represented 200 rpm? I absoluetly have not a clue what im talking about so please eleborate on why 17? Also would you stick with the 13 3/4 diameter? Any information i can gain from an experienced mind is much appreciated. Thank you sir

 

[jimmbo]

What is your engines WOT rpm range, 5000 - 6000 rpm? If so, and the tach is accurate and if the engine isn't hitting some sort of Rev-Limiter, you are only over revving by 200 rpm. A 2 inch increase in Pitch should drop it to 5800. However if the engine is hitting a Rev-limiter, then you might have try a 17 or a 19 inch pitch get a better idea of where you are. I have always let the prop engineers worry about the diameter of a given prop. You will notice that in several prop lines, as the pitch goes up, the dia. gets smaller
A light boat doesn't need a lot of Blade area, so don't lose any sleep worrying about dia. The 120 for the first few years used a large lower unit that utilized V6 props, by the 90s it was using the smaller V4 type gearcase, and smaller props

 

[WesNewell]

Assuming a 2.0 gr I'd start with a 20p minimum on such a light boat. A 13p sounds crazy low to me. I run a 14p with my 1.83gr 60hp engine on a 1000# boat and can squeeze 40mph out of it. With a properly setup 120hp I'd guess I could easily get close to 60 mph with a 850# boat.

 

[Sea Rider]

As we have seen in many post the Rule of Thumb that states 200 wot revs per pitch up or down doesn't work well with light to medium light combos. Personally would try a same brand, same diam prop with 14 pitch to lower wot rpm down around max wot rpm range factory stated. Will still achieve excellent hole shot amd gain some top end speed compared to the current 13 pitch prop.

If actual prop over revving worries you, you can throttle much less watching tach or add one more passenger to lessen over revving, fully applies if like running full hammer down.

Happy Boating

 

[Faztbullet]

Are you wanting top end only? Do you ski/tube?? We were the nations largest HS dealer and that boat should have a 17 pitch on it. The weight of that hull when loaded with 2 persons,1/2 tank fuel,gear,batterys is closer to 1500lbs...it 850 empty.

 

[Ryan hall]

Im aware, i was just trying to state that its not a heavy boat. And yes, top speed is my only goal. Just get from spot to spot tournamant fishing. 99% of the time it is only me.

 

[Faztbullet]

Try to find a 18p BRP Viper to try.....

 

[jimmbo]

I would pick a RAKER any day over a Viper. A Viper is not much different than the old basic STT props OMC made, Slightly larger dia. and a bit more cup
An Enertia may serve you well too.