Performance Question

[jakester]

Hey Guys
Question here if you can help? I have a 2000 Stratos 19ss extreme with a 2002 200hp efi merc. I have a manual 6" jackplate,
I just bought the boat about a month ago, and after reading alot of forums on performance issues and specifications, there were about 7 people with the exact same boat I have and they all say there boat goes anywhere from 65 to 75 at about 5800 to 6000 RPM. They say their prop is 2 3/4 below the pad.
This is my question, my boat runs 59-60(gps) mph 6000(wot). I have taken my manual jackplate and set it to the same measurment, I dont get any inprovement, mine is currently at 3 1/4 below the pad. I have taken the boat to the lake and moved my motor a 1/4 inch at a time high and low to see if I can get any improvments. I may gain or loose a mph with all the movement, not much difference?? So Iam assuming my boat is set at optimal height? One of the reasons I think I need an adjustment is because at 6000rpms my boats rev limiter goes off and I have to back down? why because I still have throttle left? My water PSi is about 18 - 22 at 6000 rpms.
So in closing, If i get a bigger prop with more pitch, Im guessing my rpms will decrease, which will stop the rev limiter from going off, and my prop will be throwing more water which means more performance?? :confused:

My current prop is a Mercury laser II 13 3/4x 23 stainless 3 blade
If i do get a new prop how do I tell how much more pitch to get?

thanks guys sorry so long.................help

[FishTales]

So in closing, If i get a bigger prop with more pitch, Im guessing my rpms will decrease, which will stop the rev limiter from going off, and my prop will be throwing more water which means more performance?? :confused:

My current prop is a Mercury laser II 13 3/4x 23 stainless 3 blade
If i do get a new prop how do I tell how much more pitch to get?

thanks guys sorry so long.................help

One inch more on the pitch ie: 13 3/4 x 24 will reduce your rpm by approx 200 rpm.
In Theory, the 23 will move the boat 23 inches per revolution, so therefore the 24 should move it one inch further per rev (increase in perf)
Also by lowering the rpm, you should be able to get back to 6,000 rpm by using the extra throttle you have left.
So your thinking above is correct. :)
Rich

[wickedcarpenter]

I'm set up 1" below pad and run a 25 pitch Tempest plus. WOT rpms are 5,400Not a great hole shot with 2 guys a full load,livewells filled and 48 gallons of gas.
I could redline with the 23 pitch. Max rpm on the 200 is 5,800. Blowing that motor will set ya back about $6,000 for a rebuilt powerhead put on.
Take it easy on the motor and it will last.
Brent

[TONGA]

If you are bouncing of the rev limiter with some throttle left then I would think a 25 should be a good choice and then a little playing with the jack plate, a dealer should let you try one as long as you don’t damage it.

[Damark Marine]

It does sound like a bigger prop may be in order if what you are looking for is top speed. Just remember that often it is a give & take world so if you get your best top end prop it may be at the sacrifice of planing power.

One more thing if the others are getting 70+ what props are they running, seems to be the simplest way would be to ask them? I see you say they are getting 65-75 that is a big differance in itself & the truth may lie somewhere else.

[andy capp]

Going to a bigger prop will get you what you need, but like damark said you are going to sacrifice on the bottom end. I myself would look into a 4 blade prop. It may slow you down on your top end. but it will help you plane out at lower speeds. Who the heck need to go 75 mph anyway?

[SalmonBum]

The 20' Nitro (200hp) had a 27 pitch when we bought it. It would do well over 80, but very slow outta the hole. I think we threw on a 23 and it is now a 70-75 mph boat, but will JUMP outta the hole.

[jakester]

Thanks for some of the input Guys, its not that i want to fly down the lake or river, I just want the Rev limiter that goes off about 58mph to not go off, its kinda annoying hearing the high pitch chirp......I have excellent hole shot right now, shell get up and dance in a minute.
If I can get another 7-8 mph that is great while sacaraficing a little hole shot thats what im looking to do..........I just dont know on what prop size to start at, Im assumning maybe a 25 pitch 3 blade?? I guess i will find a dealer that will let me try a couple???????

In understanding props, what does the diameter size of a prop do??
I see they range from 13 - 15 inches?

thanks again guys
------------------------------------------------------------------------
I've always made a total effort, even when the odds seemed entirely against me. I never quit trying; I never felt that I didn't have a chance to win." -Arnold Palmer

[wickedcarpenter]

Look on screamandfly.com for a prop. Lots of killer deals. I've bought a new lower unit and prop off the site.
Brent

[Gone Fishing]

Diameter can influence the speed you get, but it has its greatest affect on your acceleration and thrust. Bigger diameter is like adding bigger tires to your car: more traction or more appropriately, less slip. Larger diameters put more load on your motor because they move more water though so don't over do it. A blade moving through water does experience drag . The less blade there is (less diameter), the less the drag will be. Provided your motor and prop produce enough thrust, when you decrease your prop diameter your speed will increase a bit because there is less drag.

[jakester]

The more I read your guys post The more I learn.

Diameter can influence the speed you get, but it has its greatest affect on your acceleration and thrust. Bigger diameter is like adding bigger tires to your car: more traction or more appropriately, less slip.


I was on website and they have a slip calculator, and according to it I have 17% slip? Is this average, low, high? I know when Im going about 45+ it seems when i go into turns its like Im sliding a little bit, i dont know maybe its because I not used to having a boat go that fast? I though about investing in a hydrofoil? But just maybe if i get the correct prop my problems will be solved? Im not cavitating it just seems different from my last boat that had a 90hp motor instead of a 200hp that i currently run.


One inch more on the pitch ie: 13 3/4 x 24 will reduce your rpm by approx 200 rpm.
In Theory, the 23 will move the boat 23 inches per revolution, so therefore the 24 should move it one inch further per rev (increase in perf)
Also by lowering the rpm, you should be able to get back to 6,000 rpm by using the extra throttle you have left.
So your thinking above is correct


Thanks Rich for that input, what you said makes alot of sense. Im thinking of actually going to a 25, I have noticed from talking to a few stratos boat owners alot of them run a 25 Renegade.

[Gone Fishing]

I was on website and they have a slip calculator, and according to it I have 17% slip? Is this average, low, high?

My experience comes from boat racing but most of my props were in the 8 - 9% slippage range. On my fishing boat, I've never calculated it but to me, 17% sounds a tad high. I do agree that a 25" pitch should put you in the ball park.

[jakester]

Thanks Guys for all you input. I will update you when I get a new prop. hopefully that will be sooner than later.:)