prop size for my boat? - Maxum Boat Owners Club

gezy · 05-21-2007, 09:54 PM

can you tell me the best size prop for my boat?.

i think im under prop .(is that what you call it) it revs to much and not that fast.

i just put in a 5.7 350engine new not run yet. so i will like to do this job the same time
and stop the over rev.i cant tell the size is on it now.drive is alpha one gen 2.

seapuppy · 05-22-2007, 12:02 AM

what size boat.....I ran on my 24 a 15x19x 4 bladed prop....it was ok...but when i went to the 15x19x3bladed big eared prop..the boat really ran great..so...depends on the boat and weight .....

you can find the size of the prop on the side of the hub between the blades.......

gezy · 05-22-2007, 12:22 AM

i think its about 2000lbs 2300sc
23 or 24 foot?
plane @3500rpm then the revs just go mad with no speed.30mph on the clock.got the trim tabs on play with then same.

i was thinking with the engine that size it will get up to 50 ish?

gezy · 05-22-2007, 12:39 AM

you can see my boat in the pic gallery :wink:

seapuppy · 05-22-2007, 03:18 AM

gezy.....I think your probably having a slippage in the hub.......might wanna take it off and take it to a prop shop........check the blades too...if they are bent...you'll get a vibration and possibly cavitation......

at worst it's the hub......

Franco_2100SC · 05-22-2007, 01:24 PM

I would like to comment and share my experiences, but I cannot see the picture you refer to , when I click on Member gallery, it comes up empty. I have never posted pictures in the forum, but I do have a web page where you can look at the set up on my 2100SC

http://sempreveloce.tripod.com/

There's a good shot of the tabs and the Stainless prop that I went with. I have a 5.0 liter and with this prop RPM tops out at 4100 and if I carefully manage the tabs and the drive angle, I can get to 50-51mph.

KKKKFL

Flying_Maxum · 05-22-2007, 03:49 PM

I have a 2100 sr2, 5.7, with a Quicksilver 19 pitch s.s. 3 blade. I hit 55 saturday at about 4500 or so rpms, and I get on plane quick. I am not sure of the diameter, tip to tip it measures out at about 13 7/16, but there is no markings showing diameter, so I am guessing it is around 14". This prop was on it when I bought the boat, and I dont think I will be changing it anytime soon.

Franco_2100SC · 05-22-2007, 04:03 PM

You're probably 800 lbs lighter with the Sport Runabout over the Sport Cuddy, and with a 5.7 versus a 5 liter, I would expect that performance. I'll bet the markings for the prop are there, maybe inside the hub. Manufacturers are sneaky as to where they stamp the numbers.

KKKKFL

gezy · 05-23-2007, 06:21 PM

4878120a4019p ?.thats what i see on it.so how big can i go.will buy one then :wink:

seapuppy · 05-23-2007, 06:46 PM

it looks like your at a 19"p...so you could easily go to a 21-22" pitch if your hitting the rev limiter or going way past the 4200-4800rpm rev range the manufacturer wants the boat to run at....

what's your WOT rpm range??...Wide open throttle??..cuz that is going to dictate what prop size to use....

I still think your slipping the hub....

Flying_Maxum · 05-24-2007, 01:55 AM

Found this in an article in one of my boating magazine. Has a link to a calculator to help you find right prop size. Probably not completely accurate, but I bet it would be close.
www.turningpointpropellers.com
use the prop wizard.

gezy · 05-24-2007, 02:27 AM

well top end rpm 5000 to 5500 nuts 30mph.

now with the new engine thats no good.lol!!. it will run by the weekend

so loooks like i will get me a new prop to .

300 rpm a pitch if i go bigger.

also tell me what i need to ask for ok,my drive is alpha one gen 2.

thanks,ger

3388sam · 05-24-2007, 02:38 AM

Prop Calc
I run a SS 14 1/4" X 23" on our boat and the calc. did have it on the list. I've run the 21" pitch (which it recomends for a speed prop) before and hit the rev limiter on the engine.
The 23" runs WOT at 4700rpm and 67mph on GPS with 2 people and 30 gallons of gas as well as coolers etc etc.
So I'd say it's pretty close.

gezy · 05-24-2007, 02:43 AM

:wink: thats ths size i go for then. i like the 67 bit!!.if the wife let me hehe.

Franco_2100SC · 05-24-2007, 01:20 PM

As I recall, the 2100SCZ has a HUGE motor, not like my wimpy 5 liter. Really , one needs to match horsepower to weight for optimum performance. Also, you really need to test in near identical conditions since small variables can sneak in. On my 2100SC WOT is nearly always 4200RPM but GPS speed will be between 47 and 52 even with the tank and # of folks the same. Wind, tide, water state, and slight variations on the tabs and engine tilt all add and subtract from one another to cause the differences. Another variable that I discovered just this season came to view when the mechanic that does my pre and post season engine tune, found that the tach was reading 200 to 300 rpm lower than his meter. So I'm looking at the dash and seeing 4200 but its actually 44 or 45...

The optimum Prop is best found if you can find someone that allows you to test during a single day and bounce through several. Its an arduous task, and there aren't a lot of prop guys around that allow this. But, seek and yea shall find...
KKKKFL

3388sam · 05-24-2007, 05:25 PM

Gezy,
I was just pointing out that the prop calc is close. Our boat has a 350mag in it and much like Franco pointed out I was able to test a couple of different props from our local prop shop before choosing the one I did.
Thant is the best way to go!
So use the calc for your boat and find a local prop shop.
Good Luck - props can be kind of a mystery to find the right one for your boat!

gezy · 05-25-2007, 12:44 AM

i just got the prop off now .i think the nut was a bit loose also do you have
in and out play on the shaft .i got a lot of it i think.but some boats by mine got the same drive .same thing but a little bit less play?.do the alpha gen 2 drives do that.

gezy · 05-25-2007, 12:50 AM

seapup,

how can you tell if it was sliping?.

seapuppy · 05-25-2007, 02:36 AM

usually the when you accelerate hard..the prop will initially bite and then it will rev up really hi but you won't increase speed.....so if your prop was loose, it is possible that your prop is slipping and the hub is bad...take it off and to a local prop shop ..they can tell you if the hub is worn if your not sure....the hub is the center part of the prop and it's rubber...if it's worn, you'll see the edges of the rubber worn....
there is some play in the shaft...it's possible that you may have some slop in the shaft and the only way to really tell if it's too much or not....is to use a runout gauge......
hope this helps....

gezy · 05-25-2007, 06:01 PM

thanks all i ill tell you all how i get on. :wink: