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Discussion Starter · #1 ·
Trying to figure out what the optimum wide open throttle is on this motor to see if my prop is correctly sized and pitched. Anyone have any insight into this?

Thanks

Greg
 

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Hard to say based on how much your boat weighs and how much gear you have. On our 21 sea hunt with a 115 four stroke WOT and light gear puts me right around 38-40 mph. hope that helps
 

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Discussion Starter · #9 ·
2001 Striper 2101 Walk Around

Im not sure if it is the stock prop. Its aluminum... I really dont know what size or pitch. I can measure the diameter tomorrow but have no idea how to find the pitch. It is dinged up a little but not too bad really. Ive owned the boat for 4 years and have never really thought much about RPM at WOT until I read something about it.

Boat is about 3500 lbs empty I believe -- 4700 with full tank (105 Gallons) and 2 people.

Greg
 

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See if you can find some numbers on the prop it should have numbers around the nut area. Do you no what speed you are getting on Gps at WOT? I did a lot research and playing with my setup to get it right. I am running a 150 rude on a 20' Keywest Walkaround.
 

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Discussion Starter · #11 ·
Prop #'s and speed

At WOT I'm at about 37MPH in flat calm conditions.

The boat is shrink wrapped so I cant get to the prop without cutting the wrap. I'll see what I can do. If I cant get to it, I may have to wait the month until I pull the wrap off to start getting ready to go back in.

I'll reply again if I can get to the #'s

Thanks again,

Greg
 

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You are turning 4700 rpms at 37mph with a gear ratio 1.86 to 1.
Prop slip with a 17 pitch is 9% seems low with a beat up aluminum prop. I think something is off with the numbers or the Tach is off. I would think you should be running a 17 pitch or a 15 pitch on that boat and motor combo. If you plug in 15 pitch you get -3% which cant happen. I would guess you are running a 17 pitch.
may be 19 pitch.
 

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Discussion Starter · #13 ·
Prop says 15x17

Kwest

Do you need any other numbers? they were tough to read and I think the only other number is a serial number.

Any help or advice you can provide is greatly appreciated.

Greg
 

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Kwest

Do you need any other numbers? they were tough to read and I think the only other number is a serial number.

Any help or advice you can provide is greatly appreciated.

Greg
Has this been your Wot since you have had the boat?
I figured it was 15 x 17. Other things to look at to help with rpm is Bottom Paint, Engine condition, Motor height on transom and extra weight in the cabin.
 

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Discussion Starter · #16 ·
Yes, no change since I got the boat

Kwest -- thanks for your reply. It has been the same all along, I just figured if I can get a few extra MPH that would be good but after speaking with Ray at Atlantis Propeller (very nice guy-spent alot of time with me on the phone) have come to the conclusion that I'm in the range (4500 - 5500) and am happy with my cruise, so why mess with it.

He explained to me that changing things to get that extra few RPM's and MPH at WOT could actually hurt my cruising speed and getting up on plane.

As we all know, there are plenty of other places to spend $$ on the boat so why fix it if it isnt really broken.

Thanks again for your help

Greg
 

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Kwest -- thanks for your reply. It has been the same all along, I just figured if I can get a few extra MPH that would be good but after speaking with Ray at Atlantis Propeller (very nice guy-spent alot of time with me on the phone) have come to the conclusion that I'm in the range (4500 - 5500) and am happy with my cruise, so why mess with it.

He explained to me that changing things to get that extra few RPM's and MPH at WOT could actually hurt my cruising speed and getting up on plane.

As we all know, there are plenty of other places to spend $$ on the boat so why fix it if it isnt really broken.

Thanks again for your help

Greg
No problem Greg If you do look for a new prop I would recommend the Turbo 1
Prop it's a bow lifter and that is what are walk arounds need. I was able to raise my motor to the top hole and still trim the motor to to 3/4 up with out it breaking lose. The aluminum prop that the boat had when I bought was not even close in performance 5mph slower and 500rpm to low. Good luck and have a good fishing season.
Scott
 

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Discussion Starter · #18 ·
Bow Up

Scott

Thats funny you say that... I trim my motor WAY up to the point where I cant even believe its not slipping and it actually gets the best fuel mileage and RPM there. I have a Floscan and at the high trim it reads the most economical and as I said the speed and RPM will go up right to the point of slippage.

I look back at the motor everytime and wonder how it can be running at such a high trim. I love the Floscan meter! I got it because my fuel gauge is broken... its an issue with my tank so I'd have to replace the tank. This way I know within a gallon, how much fuel I've burned since last fill and can see where I'm getting the best mileage. Great tool.

Greg
 

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By raising the trim you are lifting the bow out water and you are running on less surface area on the boat that is going to give your highest mph most rpm and lowest Gph. What mounting hole are you on now on the outboard? If you can raise the trim that much with out slipping I think you can raise that motor at least 1 hole. The more lower unit we can get out of the water the less resistance you will have . That will increase Mph, Rpms and decrease your Gph and the best thing it doesn't cost you a thing to do it.:thumbsup: I raised mine 1 hole at time till I got the most out of it with having the prop blow out in rough seas.Can you get a picture of motor hanging on the transom with the mounting holes visible so I can see where you are now that might help.I think a lot of boats are not setup to get the most out of them when they leave the dealer. As you no with gas prices the way they are we need to squeeze every bit out of our setups as we can.
I am running a flow scan also I found my best cruise is 3,800 to 4,000 right around 30mph burning 10 to 12 Gph Flat seas trimmed out.
 

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Discussion Starter · #20 ·
2nd hole from the top

Scott

There are 4 holes and I'm currently in the second one from the top. One empty above and two below.

Is it as simple as just moving the motor up one hole? This wont affect anything else right?

Greg
 
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