60hp Prop recommendation

[TerryF]

I have a 16ft Ranger Aluminum Boat VS1670WT. It is powered by a Mercury 60HP 4 Stroke command thrust. When I got the boat it had a Vengeance 3 blade 15P SS prop. After much research and speaking with ranger they said it was supposed to come with a 14P 3 Blade SS Prop. The boat had absolutely no hole shot and took forever to get on plane. With myself and my wife in the boat. Top RPM was around 5400 rpm and 26 to 28 mph on a flat glass lake. The boat would not plane with 4 people in the boat. After much research and phone calls I tried a 4 blade spitfire in a 13 pitch. Prop diameter is 13.8 in. With this prop I got 5600rpm and 32 mph. The hole shot improved alot. I added 200 pounds of water to my live wells and got 5500rpm and 29 mph. With 4 people on the boat I lost most of my hole shot, it would get up on plane eventually, I got 54 to 5500 rpms and about 26 mph. I was hoping to get closer to 6000rpms and not loose any top end with 2 people and gear. I swapped out to a spitfire 11P 4 blade and it would go over 6000 rpms (too low) and at 6000 rpms I only got 26mph. Am I asking for to much or is the 13P spitfire as good as I am going to get.
Would a Larger pitch 4 blade with a smaller diameter work? By the way my boat is rated for a 90hp so I know I am under powered by approx 20%
Thanks for any input.

[DaleH]

FWIW I propped a heavy (floor, deck, console) 16' Starcraft weating a Johnson 60hp 2-stroke with a 'Hustler' model 4-blade 'pressed aluminum' prop by Turning Point Propellers.The new pressed props offer thin blades like SS wheels at aluminum prop proces. They also have a FANTASTIC prop pitch calculator, where you can put that exacthull and OB in. Add in real/honest numbers for the weight carried and you'llget good results.

My engine would almost hit the revlimiter if I was alone, but I couldcarry 4 and only lose a few 100 RPMs and yet still had good hole shot wven if I had 5 aboard. IMHO 4-blade props are the way to go if one willbe pushing a load. You can also trade-in props with them "to ensure you get what you need", for something like a small handling fee.

[TerryF]

I ran into someone with the same size boat and the same motor as mine. He had a 10.3X13 and said it had good performance but didn't have specific numbers. I also see there is a 10.1X14. available . Would either of these increase my RPS and maintain top speed with a good hole shot.

[ken2]

So especially with this size motor, two things.
1. they have two different size gearcases, the standard and the command thrust, so you have to know what gearcase the other guys have, cause you have different gear ratio's and prop sizes.
2. when your dealing with 10-13 pitch props, 1 inch of pitch is BIG, you have to think of it more as a percentage change vs the general 1 inch of pitch equals 200 rpm stuff.

both the sizes you mentioned in your last post are for the standard gearcase, not your command thrust. So the barrel or pipe part of the prop is considerably smaller, and wouldn't work.

As for your numbers some are kinda strange. Are the speed numbers from GPS or speedometer?

60 HP Mercury Command Thrust, 2.33 Gear ratio 5500-6000 RPM range.

15 Vengeance. 5400 RPM at 27MPH 18% slip. not good.

13 Spitfire, 5600 at 32 MPH Light negative 8% slip (very odd, i'd want to check that one again)
Loaded 5400 at 26 9% slip. (what i'd expect)

11 Spitfire, over 6000 at 26 MPH 6000 would be 3% slip, very low, but you said over 6000, so not sure where you ended up.



Looking at your numbers, the prop I'd want to run would be a Powertech SCD3 in 13 pitch.
I think if you could turn it 6000, it would put you around 28-30, its an easy prop to turn, so it should have great holeshot.
normally runs pretty flat, its somewhat sternlifting as 3 blades go.
I sell them, they ship about 4-6 weeks after you order.

[TerryF]

So the barrel or pipe part of the prop is considerably smaller, and wouldn't work. Ken I am not understanding this. Are you saying it would not fit on the motor because it is on it now and working?
Are the speed numbers from GPS or speedometer? Speedometer
11 Spitfire, over 6000 at 26 MPH 6000 would be 3% slip, very low, but you said over 6000, so not sure where you ended up. I only let it get a little over 6000 maybe 6100 to 6200 it seem to climb rps quickly so I didnt go further but at 6000rpm it was only 26mph.

[ken2]

You said you had the 13.8 X 13 spitfire. and an 11 pitch spitfire that I will "assume" was also 13.8 inch diameter.
Those are for the Command thrust, (big gearcase)

You were told by someone that they liked the 10.3 X 13, and the 10.1 x 14, so you ask about those props.
Those would not fit your gearcase, they are for the standard gearase, not yours.

That guy may have the same boat, and motor, but he has a Different Lower unit then you do.


If I were you, I'd run your 13 pitch spitfire again, and double check that speed with a light load.
Use a speedometer app on your phone, and if your in a current, run both ways and average it.
The speedometer on the motor is not accurate enough to base a prop decision on.

[TerryF]

If I were you, I'd run your 13 pitch spitfire again, and double check that speed with a light load.
Use a speedometer app on your phone, and if your in a current, run both ways and average it.
The speedometer on the motor is not accurate enough to base a prop decision on.

Ken, I will do that with my phone GPS and get back to you.

[TerryF]

If I were you, I'd run your 13 pitch spitfire again, and double check that speed with a light load.
Use a speedometer app on your phone, and if your in a current, run both ways and average it.
The speedometer on the motor is not accurate enough to base a prop decision on.

Ken,
I ran the 13 pitch spitfire again with a phone GPS, I did a few runs to double check.
I got 28 mph turning 5800 rpms trimmed. I could get a little more rpms with more trimming but the speed did not change.
I had myself and wife in the boat.
I do get good hole-shot with just the two of us. If I add two more people my hole-shot is crap.
The boat came from the dealer with a 3blade 15p vengence. poor holes-shot, poor top end max rpms was 5400 if I remember correctly.

[ken2]

I'd go 12 pitch Spitfire
but your 11 isn't too bad, strong holeshot and only 2 mph loss.

[TerryF]

I'd go 12 pitch Spitfire
but your 11 isn't too bad, strong holeshot and only 2 mph loss.

Ken,
The two MPH were from the boat speedometer and 6 PMH difference.
I figure if the Boat vs GPS are 6mph different then the 26mph with the 11 is actually 20mph by gps, so comparing the 11 to the 13 is 8mph different or am I missing something.

13 Spitfire, 5600 at 32 MPH Light negative 8% slip (very odd, i'd want to check that one again)
Loaded 5400 at 26 9% slip. (what i'd expect)

11 Spitfire, over 6000 at 26 MPH 6000 would be 3% slip, very low, but you said over 6000, so not sure where you ended u

[ken2]

Well, the speedometer is not accurate. can't really go off it.
so it being 6 mph off on one day doesn't mean its the same on the next run.
So any numbers you have with it I would not base a propeller decision on.

I'd just get good reliable numbers with GPS, and do a two way average to make sure the current isn't screwing with you.
See how much slower the 11 pitch actually is.
I still think the 12 pitch Nemesis would be the prop for you, but curious what the 11 does.

[TerryF]

Thanks ken

[TerryF]

Ken

I did a online search for a 13.8x12P prop but apparently they dont make a 12P spitfire . They make a 13 and a 11. Any idea why or if it a special order or something? Is this something you can get?

Terry

[ken2]

You are correct, they make the 12 for the standard gearcase but not for the command thrust.
So with aluminum, that is about all you have.
lowest pitch Solas makes is 13
so the only thing I'd have is the SCD3 in 13 pitch like I had originally mentioned.
as for aluminum props, there just isn't much selection.