Prop reccomendation - 21' deck boat

[soggypants]

Hello all,

Looking for a recommendation please from the forum:

[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]1) Performance issue you are trying to correct.
Cavitation when turning tight or even medium turn when tubing / water skiining. Would like better handling. Honestly, hole shot is fine, top speed is fine for size lakes I am on. [/FONT][/COLOR]

[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]2) Current prop manufacturer, model, aluminum or stainless as a minimum.

Aluminum - [/FONT][/COLOR]Solas 3511‑150‑15 15
[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]3) Current prop diameter and pitch (required).
15", 15"[/FONT][/COLOR]

[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]4) Wide open throttle RPM and speed with an average load (very helpful)
5400 RPM, 36.8MPH (using GPS)[/FONT][/COLOR]

[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]5) Engine/drive make, model, year, and HP[/FONT][/COLOR]

2006 Yamaha 150TXR 2-Stroke Series (x1)

[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]6) Boat make model, year, length and weight[/FONT][/COLOR]

[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]2006 Nautic Star Boats[/FONT][/COLOR]
[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]210DC SPORT DECK/DB[/FONT][/COLOR]
[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]21'[/FONT][/COLOR]
[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]8'6" beam[/FONT][/COLOR]
[COLOR=rgba(0, 0, 0, 0.87)][FONT=&quot]2650 lbs dry (no motor)[/FONT][/COLOR]
60 gallon gas tank


Thanks in advance - specifically, should I get a 4 blade or three? I assum stainless steel is better in every way except cost. There is a dizzying array of manufacturers. Is there really a difference between brands?

Thanks

Michael

 

[alldodge]

1) Performance issue you are trying to correct.
Cavitation when turning tight or even medium turn when tubing / water skiining. Would like better handling. Honestly, hole shot is fine, top speed is fine for size lakes I am on.

2) Current prop manufacturer, model, aluminum or stainless as a minimum. Aluminum - Solas 15 15

3) Current prop diameter and pitch (required).15", 15"

4) Wide open throttle RPM and speed with an average load (very helpful) 5400 RPM, 36.8MPH (using GPS)

5) Engine/drive make, model, year, and HP 2006 Yamaha 150TXR 2-Stroke Series (x1)

6) Boat make model, year, length and weight
2006 Nautic Star Boats
210DC SPORT DECK/DB 21'
8'6" beam
2650 lbs dry (no motor)
60 gallon gas tank

Thanks in advance - specifically, should I get a 4 blade or three? I assum stainless steel is better in every way except cost. There is a dizzying array of manufacturers. Is there really a difference between brands?

Howdy Michael

Do appreciate the method of how you provided the needed info requested in the sticky. Had to get rid of all those color, font size, and other crud so I can at least read what your asking.

Being a deck boat and not much a Vee hull so your drive is probably not low enough in the water to keep the bite of the prop going. This is a 2008 model and we can see the draft is not much



Can you provide a pic of how your motor aligns with the bottom of the hull?

 

[Scott Danforth]

where is your trim when your trying to turn? if your trimmed too high, you get blow-out (especially on a deck boat)

your in the right RPM range. if you drop in pitch, you can go to 4 blades, however if your issue is simply a motor trim adjust, why spend money.

 

[SkiDad]

i think you are propped right or close to it. some props blow out less and it's kinda a crap shoot when trying different ones. Like Scott said, hull design has a factor too. My old boat I would get less blowout when i left the trim at a neutral position. i had a stainless prop that I had additional cupping added to and it handled much better after that.

 

[soggypants]

I don't have a picture of how the motor sits witht he boat - will grab one probably later today. I experience the problem even when the motor is trimmed all the way down. Obviously it is worse if I have the motor trimmed up to cruising position.

Sorry about the fonts and stuff - didn't see that from the copy and paste.

Is there any value in going to a Stainless steel or 4 blade prop from the current 3 blade aluminum or would I be wasting my money?

 

[alldodge]

Is there any value in going to a Stainless steel or 4 blade prop from the current 3 blade aluminum or would I be wasting my money?

It takes more power to turn more blades, also more blades gives you more lift. Your prop is coming out of the water so until further understanding of what is happening, more lift is the last thing you need.

As for stainless, the blades are thinner and can supply more power to the water because of being thin and do not flex as much as aluminum. If you hit something with an aluminum prop, in most cases you need a prop repaired or replaced. Hit the same thing with SS and you might need to replace something inside the drive

 

[soggypants]

So I am not allowed to post pictures (I guess I am too new to the forums). That being said, quick update - by trimming up I was able to eke out 40mPH at 5700 RPM. Don't know if that changes anything.

​

 

[alldodge]

Now that you have posted the 3rd time you should be able to upload pics

Your going faster but the initial problem was ventilating the prop on turns, correct?

 

[Sea Rider]

Seems another prime example of OB Height/Transom Mismatch...

If prop aerates on slight choppy wavy water cond and at tight close turns when combo runs parallel to water level with trim set to neutral (90?) OB sits way high on transom, need to lower it down till those issues cancels out. If can't be lowered any further will need to chop transom down a bit till lower leg has more amount of water bed for prop to grip best and provide top thrust.

Do you think that Boat Manufacturer cares the least about which OB brand owner goes for. If you sit 3 L size different brand OB's on it, all will perform different due to lower leg height differences, some are slight shorter, some slight longer. If you don't understand or care about this not known issue, keep wasting precious boating time getting rid of the prop aeration by whichever method you prefer.

Happy Boating

 

[ondarvr]

What you're experiencing is ventilation, not cavitation, but the terms are commonly used incorrectly.

​Different props will give different results, cupped props tend to ventilate less, as do SS props, and going to 4 blades may reduce it further, and you could even go to 5 blades. There are trade offs with every choice though, so it's something you need to figure out to best meet your desires.

And just because two different brands have the same numbers for diameter, pitch and even design for a particular purpose, doesn't mean they will in any way perform similar to one another, when fine tuning it's all trial and error. If you can find a dealer that will let you try different props until you find you like it will help a great deal.

If dropping the motor one hole is possible it may be a no cost solution.

 

[soggypants]

No Title

Here are the pictures. Yes - I did trim up more to get the higher speed and RPMs. But the problem I am trying to fix is losing bite on the turns.

 

[alldodge]

To me the boat drafts very little water and that is what causes the issue. The motor could use dropping another inch but it won't help much. What may help more is getting more weight on the stern.