Another prop swap question from a newbie

[Fridge]

Just looking for some affirmation that I'm thinking along the right lines. 2012 23' Sun Catcher pontoon, 3 logs, Yamaha F150. Current prop 3 blade 13.25" - 18" SS. New to the boating thing when I bought and prop came dealer recommend. I think I have a bass boat type prop. I want to go 4 blade alum. (run a rocky lake system). 5700 rpm gets about 37 mph with 2 people 3/4 tank of gas. looking for more mid range performance, cruising 3-4000 rpm and about 20 mph. Not so concerned about top end. I have 1 3/8" room currently between tip of prop and the housing (cavitation plate?). I am looking at 14 - 17 or 14.5 - 17 Hustler 4 blade. Increase in diameter and 1" less pitch from what I read and understand should be a slight decrease in WOT and speed, but better low and mid range. Am I on the right track? Open to suggestions. How close can I get to the housing if I go even bigger in diameter? thanks in advance.

 

[steelespike]

Re: Another prop swap question from a newbie

13 1/4" diameter seems real small.A brief check of props here I didn't find any 13s.
I would say your on the right track. I think a 14.5 is a better choice and the Hustler or the Solas Amita or Rubex have a good reputation.
Rubex is the same as the Amita but with a removable hub.
I've seen 16" props discussed for alpha 1 I wouldn't get one unless I figured a out exactly what t a 16 measures. It definitely requires an anode change as do certain other props.

 

[MARV1]

Re: Another prop swap question from a newbie

13.25" diameter is for F115 down to the F60 HT, 130 2 stroke on down and dealer should have known this unless he's trying to get rid of inventory cheap. 14" to 15.25" diameter is ideal for the F150.

 

[Fridge]

Re: Another prop swap question from a newbie

Thanks for responses. I actually did another run with the current 3 blade and actually hit 6100 rpm at 35 mph. I can blow this thing up if I continue to run WOT. I'm gonna go with the 14.5 x 17, and I'm also going to go after my dealer ask why the heck did he sell me an under sized prop?

 

[jestor68]

Re: Another prop swap question from a newbie

Your motor has a 2.0 gear ratio. That equates to a 15-15.5 inch diameter prop. Shaft speed determines diameter.

 

[82rude]

Re: Another prop swap question from a newbie

Thanks for responses. I actually did another run with the current 3 blade and actually hit 6100 rpm at 35 mph. I can blow this thing up if I continue to run WOT. I'm gonna go with the 14.5 x 17, and I'm also going to go after my dealer ask why the heck did he sell me an under sized prop?

theres quite the range of props for that motor.seeing as how your hitting 6100 id try if possible a 14.5 x 19p as a starting point .I would believe you have a rev limiter on that motor and it is doubtful you will blow up before you hit it.in actual fact at 6100 rpm you are 100 rpm over the range of 5-6ooo rpm.my etec has a range of 5-6000 also and I know for a fact at 6250 I hit the rev limiter as I too had to select a prop for my application.not only did I feel the rev limiter but the mech showed me on the laptop exactly what day and time it happened.so in my case I adjusted up from 15p to 17 p and am now dead on .

 

[Fridge]

Re: Another prop swap question from a newbie

Yikes, now you guys are throwing enough info around that I'm a little confused. So I currently have a 13.25 x 18" 3 blade SS that gets me 35 mph at 6100. Going to 14.5" diameter 4 blade should do what, reduce RPM's by 200 - 300?? Then the 18" to 17" pitch should be a trade off for RPM from 3 to 4 blade?? Going up to 14.5 x 19 " pitch won't that be -200 + -200 (-400 approx), which might take me too low in RPM. Going 15" like Jester describes, where would I go with pitch using the rules of thumb? I realize I'm going to have to slap one on and do a run. Just hoping to get close the first time. Talked to a couple of shops (near me in Barrie Ont) and they are finicky about returning props.

 

[82rude]

Re: Another prop swap question from a newbie

not trying to mess you up sorryeven at -4 to 500 rpm you said your wot was 6100 so you would be at lets say 56 to 5700 rpm.problem is every boat and motor combo will and does react differently to prop changes.my boat is very tolerant of prop changes as I can go from s/s to al and from 3 to 4 blade any way I want and lose or change very little as long as I stay the same pitch.have you tried something like the merc prop calculator to maybe give you a starting point?going to a 14.5 x19 I really don't think your going to lose a lot of rpms with that big motor.you got to start somewhere.here,s just a suggestion.go with a vortex hub system and 2 props ,one 14.5 x 17 and 1 14.5x 19 .you only really need 1 hub for now.sell the s/s prop to help offset the cost.just a suggestion .that s/s has got to be worth a few bucks as long as its not damaged in any way.sorry !I see you want to go 4 blade so make that a rubex hub system not a vortex.also the beauty of a rubex hub system is you can sell the prop you don't want if you so choose and all the buyer has to do is get the proper hub for his motor if its a different brand.

 

[82rude]

Re: Another prop swap question from a newbie

from my posts please don't get the impression im some kind of expert or such about props.im just an average joe trying to help.in the interest of full discloser I have a friend that's a prop rebuilder and seller so I can try props to my hearts content .its good to have a buddy that does that.

 

[Fridge]

Re: Another prop swap question from a newbie

Rude, no worries. Appreciate all the info I can get. Great that you have the access to props to play around with. I'm gonna hit up my dealer re: the under sizing, then see what he has kicking around the shop that would be the right size (or close) so I can do a trial run. When I get down to picking the final config, then I start talking turkey with him.

 

[Fridge]

Re: Another prop swap question from a newbie

Back after playing around with a couple of new props. Got the dealer to swap out to a 14.25 x 18 3 bl SS (Yam Perf.), got to 4900 RPM WOT, 34 MPH. Motor did not sound happy with more than 2 people in the boat. Also got that 14.5 x 17 4 bl AL Hustler. 5300 RPM WOT, 34 MPH, liked the stern lift, got better mid range speed and plane angles.
So, have talked the dealer into another swap (might be out of chances after this one). I asked why I wasn't using the Reliance blade that Yammy says is made for my F150. They said good idea, and we settled on a 14.25 x 17 3 blade SS. Different cupping than the previous 14.25 x 18 3 bl(made for a V6 motor). They are saying I should get 5600 RPM/36 MPH. I'm also going to attempt a swap out on the 14.5 x 17 4 blade AL for a 14.75 x 15 4 bl AL Solas Rubex to see if I can get the WOT up.
Lastly, I'm on hole #2 on the mount, and at 4,500 RPM on either of the current props I am not seeing the cav plate get out of the water (totally covered, no exposure). Pontoons have different water action at the back, but should I still be trying to see that plate at least get exposed somewhat? Moving to hole #3 will likely up my RPM slightly and maybe get that plate up, but am I going to have more ventilation problems than not? Thanks

 

[jestor68]

Re: Another prop swap question from a newbie

Keep trying different props until you get the one that turns at least 5500 rpm(your motor's rated hp rpm).

Go by where the AV plate is in relation to the hull(tube) bottom; should be about even with the bottom.

Don't worry about being able to "see" the AV plate while under way unless you have a bass boat, or other high performance type boat. My AV plate(Mercruiser) sits 2 inches above the keel, and you really can't see it under way because of the way water rises immediately after leaving the keel.

When you get going fast enough to straighten out that water flow, you really don't want to be hanging off the stern trying to see the AV plate.