Comparison Shopping....

[WanabeBoater]

I have a 1994 Starcraft 2010ss 5.7L 235hp 20' bowrider that weighs 3500lbs. My current prop is 14.25 X 19 RH. I am looking at leaving the alum prop for a SS prop. I have been looking at the Rapture, Laser 2 and Turbo props. Has anyone had any experience with these props on a similiar boat? And if so, which would you prefer? I am looking more towards top end speed. Thanks

 

[Silvertip]

Re: Comparison Shopping....

How do you know you have not already reached top speed? Top speed is whatever you reach when the engine is reving at or near is maximum recommended wide open throttle rpm. Without any current speed or rpm info we can't make concrete suggestions unless someone with an identical boat has done the experimenting for you and has the same normal load you do. Make some test runs with your normal load and note maximum rpm and speed while playing with trim settings. If the maximum rpm you see is already at the upper end of the recommended range then the only changes you need may be for a more efficient prop, not necessarily one with more or less pitch. That change may net a couple of MPH. If the engine is over reving you need to go up in pitch and if it does not reach the upper limit, you need to go down in pitch. Check with your dealer and see what they recommend. They may also provide several props for you to try. But then don't stab them in the back by buying the prop somewhere else.

 

[WanabeBoater]

Re: Comparison Shopping....

Silvertip, Thanks for the info..I am currently running 4200rpm, while suggested WOT is 44-4600. My speedometer might be off, but I'm currently running 52-53mph. If I were to go down in pitch and gain the extra rpm's...wouldn't I end up losing my top end?

 

[Crownie2]

Re: Comparison Shopping....

Not likely - your engine should make more power at the higher RPM's.

Looks like you need go down in pitch a little...

I have experience with the Turbo and Laser and think you would be pleased with either.

 

[Silvertip]

Re: Comparison Shopping....

You are at the low end of the RPM band. Going down in pitch would definitely help hole shot, help with water sports, and while speed may be affected, chances are it will at least stay the same. Total effect depends on the type and efficiency of the prop you ultimately end up with. Check with a dealer in your area. Many of them have a trial program that allows you to try various styles and pitches before you buy. I always like to remind folks that when you work with a shop, don't stab them in the back by buying the prop elsewhere.

 

[WanabeBoater]

Re: Comparison Shopping....

I have found a dealer that does allow one to try several different props..do they install the props for you while in the water...or do I have to change the prop myself.

 

[WanabeBoater]

Re: Comparison Shopping....

I have found a dealer that does allow one to try several different props..do they install the props for you while in the water...or do I have to change the prop myself.

 

[Tail_Gunner]

Re: Comparison Shopping....

Here come's the 4 blade band wagon, on the I/O boat with the heavy rear motor i firmly beileve (for now 8)) a 4 bladed prop lifting the rear out of the water reducing drag enhance's the boat's all around preformance and speed.

Watching and experimenting with my own, the 4 blade was a better preformer, i just wish Stilletto would have made a 21p 4, had they i am quite sure it would have given me higher speed result's than there 3bl did. Aka

1. 20 p 4bl SS 54 mph @ 5000 rpm Stilletto Bay Pro

2. 22 p 4bl SS 53.5 mph @ 4400 rpm Stilletto Bay Pro

3. 21 p 3bl SS 55.3mph @ 5000rpm Stilletto ADVANTAGE II
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19 p 3bl AL 49mph @ 5000 Factory Volvo prop alum and hitting the rev limiter

That is where i started from

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I was going to get one for a project boat i have going but i noticed the leg (Merc) rides farther down below the hull than the Volvo being desrcibed above. Listening to walleyehed i believe the fact that the volvo ride's (cavitation plate) higher it was in part responsible for the huge speed gain (Here's a pic)

So as to brand Stilletto............Until Merc get's there 22-23p enertia's avaible.......:devil:

 

[Crownie2]

Re: Comparison Shopping....

Not trying to start a big argument here, but it appears the three blade Stilletto is a little more efficient than the 4 blades, in your application...

Perhaps it had other characteristics you did not like??

Bob

P.S. - I would like to see what a 21 or 22 Enertia would do for you!!

 

[Tail_Gunner]

Re: Comparison Shopping....

In top speed it was, but remeber the 20 had a speed of 54, had it been avaible in a 21 it would have out run the 3 blade.

Actually i took the number's i posted a while back and used them on the prop slip calculator, Indeed the 4 Blade out ran the 3 blade, i used the same slip values and here's the result's

Again this is only speculation, there is no 21 4 blade i could run to substantiate this. However i did run a 22 but could only turn 4400 rpm @ 53.5 to much there.

1 person 215lbs & 200lbs weight & 37 gallons of gas

19 p 3bl AL 49mph @ 5000 Factory Volvo prop alum and hitting the rev limiter

22 p 4bl SS 53.5 mph @ 4400 rpm Stilletto Bay Pro

20 p 4bl SS 54 mph @ 5000 rpm Stilletto Bay Pro

21 p 3bl SS 55.3mph @ 5000rpm Stilletto ADVANTAGE II

_____________________________________________

1.66 gears @ 22p @ 4400 = 55 actual is 53.4 = 4%

1.66g @ 20 @ 4900 =TS 56 actual is 54= 3%

1.66 @ 21 @ 5000 = TS 60 actual is 55.3 =8%

1.66 @ 19 @ 5000 = TS 54 actual is 49 =9%
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What cant been seen here is how high the 4 blade prop's raised the boat,from the driver's positon there was no longer any wake coming from the side's of the boat just straight out the back, between the lifting properties the prop has, the higher cavitation plate placement and running less wetted surface made the difference............. Now watch Walleyehed come in and burst my bubble..........8)

 

[Crownie2]

Re: Comparison Shopping....

Wouldn't you asume the 21 4 blade would run rpm's right about in between the 22 and 20 - in other words at about 4,700 rpms?

Even at 3.5% slip (which is amazing by the way) you would be running 54.3 - less than the 3 blade.

Bob

 

[Tail_Gunner]

Re: Comparison Shopping....

There's more to the Stilletto than just pitch, i believe the cupping is having a lot of influnce here, If you plug in a 21 pitch (effect's of cupping) you would find number's a little bit more reasonable.

Notice the slip on the 3 blade it's still very low but more in reason (8%} Some other funny thing's was the big drop in rpm going to the 22, almost 500. I really didnt have time to see if the motor was top form, it's actually due for inspection next week and that might shed some light.

In theroy what you are saying sounds right, but i would really like to have run a 21 4 blade just to see how big of dip it would have taken.

But there's the pic

 

[Crownie2]

Re: Comparison Shopping....

Is that trim guage right?

I know they vary depending on how it is set up but it looks like very little trim is being used...

 

[Tail_Gunner]

Re: Comparison Shopping....

Is that trim guage right?

I know they vary depending on how it is set up but it looks like very little trim is being used...

No it is not right, to this point i have not taken the time to set it up correctly. However when i was trying to see how well the prop's preformed, i would trim both in and out trying to find the sweet spot for max speed.

A few variatoin's i noticed with 4 balde's is they rode smoother, they could trim up quite a bit further, actually got a 6-7' rooster tail (lost speed though), and when @ wot you would actually have to trim down a bit to get the bow to cut a 2 foot chop..... it would get pretty ruff some time's. The 3 blade's involed less trimming and were faster at the same rpm, but then again they were pitched higher.