Trying again on prop question - more data this time

So, posted earlier asking for some input - didn't get any so did more research.

1995 SeaRay 4.3 with Alpha One outdrive. Original prop was 13.75 X 21 aluminum and replaced it with 14.25 X 20 in stainless. Stainless prop is by company called "Turbo" is what they called it, if I recall correctly.

Both props got me WOT at 4800 so matched pretty well - about 50-52 MPH smooth and lightly loaded.

Need better hole shot and pulling for watersports - some reasonable options in four blade look like - various manufacturers:

- 14.50 X 17
- 14.00 X 18
- 14.25 X 19


Are there any sizes I missed?

Any recommendations or thoughts?

Would really appreciate some help ... thanks!

Re: Trying again on prop question - more data this time

Put on nauticaus trim tabs or pm me i will buy the prop

Re: Trying again on prop question - more data this time

I can't be too specific but Usually when going from 3 to 4 it is suggested to drop one inch in
pitch.If your going from ss to al your results will be more unpredictable and changing brands further complicates things.A 4 blade will improve hole shot and low to mid range performance.
Handling should be crisper at speed and at the dock.You will likely lose some top end.
Trim tabs will also help hole shot and improve ride and trim at a very slight increase in fuel use.Various tests have indicated best fuel use is with the tabs fully retracted on plane.

Re: Trying again on prop question - more data this time

Since had a pretty good all round prop in the Turbo 3 blade (with vent holes), I decided to really focus on low speed handling and pulling out of hole ... got a QST 5 (High Five) and ran it yesterday with both 5 blade and 3 blade props and collected some data:

Calm water, about 80F, driver plus one passenger, center glass (bowrider) open, with GPS.

QST5

2.5-3 sec hole shot (just moving for steerage then full throttle, full trim down) until bow dropped to plane. Boat didn't labor to get up and then bow down, it just sort of popped up and then flattened. Bow still rose, but not as much and for not as long. Put the passenger in the back and wasn't much difference.

Yanking it around at very low speed, it just sort of hung on the prop without fuss at very high turn rates, don't think I ever got it to cavitate - planes down to around 14-15 MPH and then slowly dissolves off plane

Very little porpoising at higher speed trimmed

3000 RPM trim down (21.3MPH), trimmed a bit but maintaining 3000 RPM (21.1MPH) ... slip 28.6

4000 RPM trim down (32.2MPH), trimmed up a bit more and pulled back to maintain 4000 RPM (32.8MPH) ... slip 19%

4500 RPM trim down (36.7MPH), trimmed up a bit more and pulled back to maintain 4500 RPM (37.7MPH) ... slip 17.3%

WOT was 4800 RPM trimmed down (39MPH), trimmed up a bit more and let run to WOT at 5000 (I know is over RPM) was 42MPH ... slip 15.5%

QST not finished nearly as well as the Turbo - (looks like the blade edge had been roughly ground down and left unpolished) but probably is better value priced since I think I spent close to $400 on the Turbo over 10 years ago

3 Blade Turbo

5-6 sec hole shot, bow comes way up and hangs there for about two seconds and then moves rapidly down. Much more dramatic behavior

Yanking around at low speeds and high throttle can induce cavitation without too much effort ... doesn't hang on the prop the way 5 bladed QST did

Easy to get it to porpoise at higher speeds trimmed up

Forgot to check loss of plane speed, but was higher and much more dramatic coming off plane

3000 RPM trim down (24.5MPH), trimmed a bit but maintaining 3000 RPM (24.8MPH) ... slip 17.8%

4000 RPM trim down (35.5MPH), trimmed up a bit more and pulled back to maintain 4000 RPM (36.5MPH) ... slip 9.5%

4500 RPM trim down (40.4MPH), trimmed up a bit more and pulled back to maintain 4500 RPM (41.4MPH) ... slip 8.3%

WOT was only 4600 RPM trimmed down (40.6MPH), trimmed up and let run to WOT at 4790 RPM was 44.9MPH ... slip 5.5%

Ha - so much for the 50 MPH "indicated" on the speedo! Speedo about 10-15% off ... pretty typical, I guess.

Do the slip rates make sense?

So, net difference at something approaching a trimmed up cruise speed is about 4MPH and max speed at trimmed up WOT (4800 RPM) is about 5-6 MPH difference. I'll try the QST5 next week on the lake with skiers and evaluate it further.

What do you guys think?

Re: Trying again on prop question - more data this time

I'm surprised at the high 5 slip numbers.But it obviously does what it is supposed to.
Grips the water,gets on plane bingo! stays on plane at crawling speeds.I don't think they are noted for speed.Obviously excellent for water sports.
Best mpg should be with the turbo. For the money It seems to me the high 5 is overkill and a 4 blade Solas Amita at about 1/3 the cost would do close to what the high 5 did and might produce better mpg.

Re: Trying again on prop question - more data this time

I agree on it sounding like overkill, and perhaps the Solas would be better overall - however, if I recall the Solas was Korean or Taiwanese? I am trying to do my part - I am willing to pay more for US made items ...

Any thoughts on a four blade Merc or Quicksilver or other US manufactured solution? There are a couple of options in same price range...

I guess reason I went with QST5 was that it is sort of a pure play watersports that I could switch to when needed and stay with the pretty good Turbo the rest of the time as a more MPG and speed oriented solution ...in other words, I didn't want another broadly good prop with slightly better out of hole, but wanted a great out of hole ... I was, however, disappointed with 6 mph loss of top end, hoping it would be more like 2-3

Re: Trying again on prop question - more data this time

If you take a closer look at your numbers you will notice that slip goes down as speed increases....and the heavy bite the turbo gave on launch.....Turbos have great lift and a lot of bite...Props with high lift qualitys will generally create less wetted surface which in turn generates higher speeds and lower slip numbers..

"""5-6 sec hole shot, bow comes way up and hangs there for about two seconds and then moves rapidly down. Much more dramatic behavior""""


That bow coming up is the turbo biting the water trying to push the hull on top of the pressure wave.....If you would add trim tabs they would "LIFT" it out along with the prop pushing it out. Acutally i am quite sure you would extremely happy with the result...

Good info thank you for the info.