1986 Century 3500 LX 20FT Bowrider Prop

[TheHunter990]

Boat:
Weight with fuel right around 4000lbs. (no people on board)

Engine:
We have a Vortec 350 putting out about 300HP, never dynoed, but that should be close. Thinking WOT should max with light load at 5K RPM.
Recently re geared the Alpha One drive to 1.5 (was 1.98). All the props we were running (had 20" mercury 4blade, 21" mercury 3blade) are now to big so I'm looking for suggestions on what to get next.

Props:
Currently we have tried some cheap smaller props, both aluminium:
14.25x21" mercury, we get 4100RPM with a light load of about 4500 lbs and 42MPH GPS.
14.25x19" turning point with vents, we get 4600RPM with a light load of about 4500 lbs and 47MPH GPS.
14.25x17" turning point with vents, we get 4800RPM with a medium load of about 4900 lbs and 45MPH GPS.

Goal:
With a light to medium load to be able to hit 50MPH
More important to to plane out quickly, we mainly do tubing and wake boarding.

We tend to smash props at least yearly so I'm a little wary of expensive stainless props.

 

[Texasmark]

Do you have a propeller shop handy? Lots of times they will loan you one to test after you tell them your requirements. You take it put it on, take data and get it off before you scratch it. Keep it up till you have what suits you. It costs more but you get what you were after in the first place.....satisfaction which could be the cheapest way to get it if your were unlucky in your guessing game; shotgunning props.

 

[Scott06]

With your comment about wakeboarding and tubing would suggest staying with a 4 blade. This is basically how I use my boat (21 ft 5.0 vortec) , lots of people in it and one or more behind it. Have had real good luck with Michigan Vortex 4 blade, thinking an 18" pitch based on your comments. If you look here and on line about $95 -110 delivered currently. Unlikely you find both 50 mph and good holeshot for water sports, generally one or the other

 

[jimmbo]

You say the engine is 300 hp, Ok, at what rpm is it making its peak power? Did your engine builder provide that?

I'm very partial to the Enertia Prop by Mercury, it is one of the few props that Mercury boasts of improved holeshot and top end. It is not the cheapest prop on the shelf, but sometimes you do get what you pay for. Been running one for 10 yrs on an 18ft with 5.7 VP 1.51:1 gears 20" pitch. With the 2bbl it hits 4800 - 4900,

 

[TheHunter990]

Thanks for all the replies so far.

You say the engine is 300 hp, Ok, at what rpm is it making its peak power? Did your engine builder provide that?

I was the engine builder and have no sadly have no idea, can only guess. What we have is a stock marine vortec 350 engine with a few mods:
* Comp Cams XM270HR: http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=202&sb=2
* Edelbrock Performer RPM Vortec Intake Manifolds 2516
* Edelbrock Marine Carb 750 (soon to be a 600)
* Stock Flame Arrestor

Using camquest simulation, I get this guesstimate.
Peak HP: 310 HP @ 5000 RPM
Peak Torque: 333 FT LB @ 4500 RPM

It would be fun to hook up to a dyno, to know for sure.