prop selection help

[sima]

Hello everybody.

Need a recomendation for the new prop.

I 2004 185LX Stingray and need to change the prop.

I have 3.oGL-CVolvo Penta engine. It uses SX / Cobra Drive (Single Propeller).
135 HP, WOT range 4200-4600.
Currently I have 14 1/4 x 23 ph Volvo Penta 3850303 prop.

Being in Minnesota, I will be using this boat on the lakes or rivers mostly for family recreation.

It looks like my options are:

Michigan Match Aluminum Propeller
Black Diamond with Flow Torq Hub Aluminum Propeller
QL Aluminum Propeller

What prop would you recommend? I would like to stick with Aluminun prop.

Thank you in advance,

Eugene.

 

[rndn]

Re: prop selection help

You don't state what your current rpm's are at WOT so make sure you match up to the correct pitch to achieve the suggested rpm's.
Just a thought for you is that usually the more expensive props are expensive because of the R&D work to get a great prop to work better than the cheaper ones.

 

[sima]

Re: prop selection help

Being a new to the boating...what do you mean by

'what your current rpm's are at WOT '.

Does this mean what my RPM when the boat levels on the water?

 

[rndn]

Re: prop selection help

At full throttle with the boat trimmed properly, what are your rpm's at? WOT is wide open throttle. You have staed what the rpm range is for your motor, but you didn't say whether or not you operate within that range or if you stay at full throttle can you go past the max rpm's? Or on the other side of the coin at full throttle you can't quite get your rpm's into the suggested range.

 

[sima]

Re: prop selection help

RNDN, thank you for the explanation. I took out the boat twice and when I am at full throttle my RPM is at 4000 to 4100. I can't go past that.

Eugene.

 

[rndn]

Re: prop selection help

Then you should look for a 22 inch or a 21 inch prop. 22 would be ideal but there are not many 22 inch props out there. A 21 inch prop would increase your rpm's by about 400 bringing your max up to 4500, although you would probably only see 4400. A general rule of thumb is for every 1 inch of pitch change you should see a 200 rpm change at WOT. Drop to 22 inch and your top rpm's would go to 4300-4400. Drop to a 21 inch prop and you should see 4500 to 4600. Dropping pitch will also help you with hole shot and really take some strain off of your engine.
Does your current prop have any cupping to the blades? You should be able to see the cupping if you have it as the blade instead of a nice smooth transition to the end of the blade, a cupped prop will have a very pronounced additional over-bend to it. If you don't have any cupping, then you will do better with a cupped 20 or maybe even a 19 inch prop. Cupping reduces WOT rpm's by 150-300.
iboats.com does sell several varieties of props and also offers an exchange program if you're not happy with the prop's performance, although make sure when you make the purchase, you know the details of this offer. To be sure you should really call in this order so you can discuss the details of the exchange program with a real person.
Here is a link to Mercury website that discusses all of the prop terminology for you so you fully understand what you are buying. Please feel free to ask as many questions as you have and I'm sure the forum members will jump right in there.
http://sites.mercurymarine.com/port...26_49291:126_49299&_dad=portal&_schema=PORTAL

 

[sima]

Re: prop selection help

RNDN, thanks once again. So should I stay with the same 14 1/4 diameter and just decide on the pitch? My prop does not have any cupping.

Regards,

Eugene.

 

[rndn]

Re: prop selection help

The diameter as long as it fits your motor/outdrive really doesn't do a whole lot. Work with the pitch.

 

[sima]

Re: prop selection help

RNDN, thank you.