prop question

[rens914]

hi guys
have an issue here
own a 2300SCR with a 4,3 l 6-cil vortec engine (new) and a alpha drive
the engine runs 5400 rpm on FT
it has a slightly damaged 3 blade prop size 16x16p
want to keep this prop as a spare but what other prop must i mount
stay with a 3 blade and increase the 16p to ?
or
go to a 4 blade prop
everybody gives me different answers
the official dealer even states that the 3 blade 16x16p isn't original where as a propeller specialist says it sure is
???????? :confused:
help
rens

[seapuppy]

well....your a bit under propped from what I see.....your WOT range should be about 4400-5200 rpm max....meaning when you push the throttle to wide open and trim the boat out to get max rpm/speed....you should not be over 5200 rpm....so...going to a 16xanything larger will help reduce your rpm to within range....
so...going to a 16x19"x4 bladed prop will do 2 things for you...reduce your rpm to the right rpm range...give you a smoother response and less vibration than from a 3 bladed prop....I'd look at increasing pitch and maybe even using a 4 bladed prop......


SP

[rens914]

thankx for youre reply
bought myself a 4 blade 16x17p prop
this should bring my max rpm at FT to max 5100 without loosing top speed
can swap it in the spring for a 16x18 or 16x19p but the guy thinks that with the 4.3 vortec this should be the one.
gr rens

[seapuppy]

your welcome and report back your results......



SP

[Beaumon]

I need to look at my prop but I have basically the same boat I at WOT I get 48 MPH at 4000 RPM. I think I need a tune up. Just bought the boat, so I'm going to have them do a once-over and replace all fluids.

Maxum 2300SR

[seapuppy]

at 4k rpm your over propped...so you would need to reduce your pitch on the prop.....a tune up is always the thing to do...

let us know how it works out
SP

[Beaumon]

would it make more sense at 4000 RPM to go 38 MPH?

-Beau

[seapuppy]

yeah cuz your prop is not able to push the water....making only 4k rpm isn't in the optimum engine range..the torque can't be applied to the prop as it's meant to have....so there could be several other factors to you not hitting wot range...is the boat in the water??is the hull clean....is the engine freshly tuned and timed properly.........what pitch and diameter prop do you have....


all of these factors plays into you hitting the wot the boat is supposed to run at..

SP

[Beaumon]

Well, from all the other posts I have seen, looks like I have the wrong prop? I still am going to get a tune up Feb 7.

Current prop: 1912P17

So what should I go buy? Do I gain power and lose speed with your suggested prop? What is the goal for speed and RPM to be at WOT?

Also, for waterskiing or wakeboarding, should I get a different prop than a cruising prop? I have no problem keeping 2.

Sorry for asking such noob questions. And thank you very much for your help.

[seapuppy]

well..the goal is to get the engine operating in the correct torque range...so..if your owners manual says the engine should reach WOT at between 4200-4800rpm....your properly propped....your top speed is dependant on several factors...ie wind..wave..current....hull condition..etc...
now for wake boarding....you need a prop that will get you out of the hole faster...so that's going to be a shallower pitched prop..so if your running a 15.5x19" pitched prop....to get better hole shot...your going to want to run a 15.5x17 or 16 prop....of course your wot is now in the 5200 rpm range...make sure you don't run it that fast....

SP

[ed & inge]

hai beaumon..

when i had a boat for skiing i used a high five stainless steel prop.....

take a look at the links....

http://www.propline.com/Select-Boat-Props-By-Brand/Mercury-Propeller-Company/High-Five-Stainless-Steel-Propellers/main.htm

http://www.go-fast.com/mercury_high_five_propeller.htm

this is what you need........your boat will jump out of the water within seconds......top speed will be the same.......if you take the high five it's not nessacerry to buy an other one for cruising....you can do both with them........so your old prop can be used as reserve/backup prop.....

if you want more info, google high five or raker propellors (raker brings you an higher end speed) i prefer high five

greatz, ed

[shrew]

Ditto to Seapuppy's statements. Unfortunately, boats are not like cars and you can't really look at speeds. The key factor is Max RPM range. First look at the Max. RPM range for the motor. Then look at what RPM you're actually reaching at WOT. Over the Max. range and you;re underpropped. Under the Max range and you're overpropped. While it is true that going down in pitch will increase max rpm's, it will also increase acceleration, which will decrease time needed to get up on plane. However it will also reduce top speed. Increasing pitch will decrease max. RPM. However it will increase time to get on plane, but also increase max speed.

There is a fine line between being able to cruise at relatively the same speed at a lower rpm vs. exponentially increase the load placed on the engine. Likewise, improving your holeshot will force you to ride the thing like a rented mule when trying to cruise at higher speeds. But the goal is based on what you're trying to do with the boat. As long as you stay within the Max. RPM range at WOT you're good.

I'd find a prop shop that is willing to work with you by allowing you to swap out props to find the one that is best for you boat and boating needs.