Seeking input on new prop for Starcraft pontoon

BuckyBadger

Seaman Apprentice
Joined
Mar 20, 2010
Messages
46
We replaced the prop on our pontoon at the end of last season. I don't know what original prop was but it ran approx 17mph @ 5800 rpm - which seems a little low compared to some other set ups I have seen. The new prop is running well below the rpm range and unfortunately, the local business we used is going through a 'transition' so I am looking for some guidance.

As a secondary question what kinds of speeds are people seeing with similar setups?

1. Year, make and model of boat - 2008 Starcraft Limited 206 RE CR (pontoon)

2. Length, width and base weight of boat, look for boat decal on back of boat 20 ft; 8.5ft; 1800+ lbs
2a.What is the maximum recommended HP for your boat - 115

3. Number of people and gallons of gas normally on boat and what do you use the boat for
2 Adults and 2 children, frequently have additional passengers but for the most part just the family. Recreational boating. We bought it as a comfortable family boat thinking we could pull small children on a tube. Plan was to get something bigger once they were older but we could use this to get started.

4. Year, make. manufacturer and model of motor and recommended Wide Open Throttle (WOT) range
2008 Mercury 60hp Bigfoot 5500-6000

5. HP and gear ratio of motor IMPORTANT
60hp; 2.33:1

6. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a straight edge under the keel and sticking out to the anti ventilation plate for a reference
Pontoon Boat - Not sure exactly but engine mounted on lowest set of holes and AV plate is well below bottom of pod

7. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating.
RPM:5100-5200; Speed(GPS):16mph; No. of people: 2 Adults 2 Small Children; Gal. Gas: 12

8. Make, model, diameter, pitch, number of blades and whether SS or aluminum prop and does it have a hydrafoil, dolefin or trim tabs
Not sure of make but is 14 x 10 / 3 blade aluminum pontoon prop

9. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way by just pushing the throttle at the helm and not at the carburetor, checked compression, and looked at the plugs and checked spark as well as timing and advance, all of the foregoing could be the reason your prop is not attaining full RPM
No - but engine is serviced regularly and appears to be running optimally

10. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations and does the prop show any damage that you can see.
Get back into correct rpm range and additional speed - From my experience 20 mph doesn't seem unrealistic, but I could be wrong.
 

BuckyBadger

Seaman Apprentice
Joined
Mar 20, 2010
Messages
46
Re: Seeking input on new prop for Starcraft pontoon

Hello... is this thing on <taps microphone>:D
 

tdrudd87

Petty Officer 1st Class
Joined
May 28, 2009
Messages
288
Re: Seeking input on new prop for Starcraft pontoon

My spreadsheet is saying that is close to 20% slip. I am def not a pro, but would look at a 4 blade, and loose a few inches of pitch. I think the old prop probably had a little less pitch, for +1mph and 600 more revs.

Might just be as fast a pontoon at 50% of rated power will do. I wouldn't buy a new prop over 2mph.

Terry
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Seeking input on new prop for Starcraft pontoon

As far as slip a pontoon will have higher slip than a runabout.
I'm Assuming that is a 4 stroke;according to the chart doesn't appear there is a 2 stroke big foot.
It appears the smallest prop is a 9 inch At least here at iboats.That will give you some rpm.As far as your speed 17 is at the low end I'd say 20-21 would be real good. If you have no ventilation(cavitation)problems you could try raising the motor a couple of holes.won't gain much at pontoon speeds but every little bit helps.
Carefrul weight distribution might help as well.Check that the motor is in excellent tune and the carb is opening all the way.
Did a little research with your gear ratio I think it should perform better than that with the 10" maybe even an 11. Maybe the 4 stroke struggles more than a 2 or the throttle doesn't open all the way.Or its set way too deep im the water.
 
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BuckyBadger

Seaman Apprentice
Joined
Mar 20, 2010
Messages
46
Re: Seeking input on new prop for Starcraft pontoon

Just to clarify it is a 4 stroke with EFI.

My main concern is just getting back within the correct rpm range as I've heard that it can be hard on the engine if it is over propped.

I'm not too worried about the speed, I did by a pontoon after all;). But like steel said every little bit on a pontoon makes a difference. And since I'm going through the trouble anyways might as well at least ask.
 

BuckyBadger

Seaman Apprentice
Joined
Mar 20, 2010
Messages
46
Re: Seeking input on new prop for Starcraft pontoon

Did a little research with your gear ratio I think it should perform better than that with the 10" maybe even an 11. Maybe the 4 stroke struggles more than a 2 or the throttle doesn't open all the way.Or its set way too deep im the water.

Thats kind of what I was thinking. Just wasn't sure where to start. Engine too deep, the new elephant ear prop. As a starting point I'd just like to get the prop that is 'right' (well as right as possible anyways) for the boat then start adjusting motor height and what ever else.
 
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