What speed Can I go with Nitor SF185

[haikt]

Hello,
I have a Nitro SF185 sport with a Force 120 and a lazer2 (20P) prop. 18.5 Feet.
I am being told that I should get lot more then I got now.
Please tell me what you would expect from this combo based on your experiance.
Thank you

 

[Silvertip]

Re: What speed Can I go with Nitor SF185

The speed you get is determined by a number of factors. 1) what condition is the engine in. Is it making full power. 2) Has the engine been set up properly on the boat (mounting height optimized for the prop you are using). 3) Condition of the hull. A dirty hull will be substantially slower than a clean hull. 4) The load you are carrrying. Extra gear and adult beverages, etc., will slow you down. I have no experience with Force engines on that particular boat so other than the above, I can't help you.

 

[kenmyfam]

Re: What speed Can I go with Nitor SF185

As Silvertip. So many unknowns.
You just asked "how long is a piece of string"

 

[haikt]

Re: What speed Can I go with Nitor SF185

Thank you very much for the info,
I underastand that all the factors play a big effect on the speed.
I wanted to know ballpark figure like 45 or 55 lets say so when I test it I know I am looking at ok engine.
Boat is very clean, engine is on the last hole down I cant get it lower.
Thank you

 

[180shabah]

Re: What speed Can I go with Nitor SF185

Why not compression test the engine to determine if it is "ok"?

 

[haikt]

Re: What speed Can I go with Nitor SF185

Thank you for all your responses.
I ask the question due to being told that the boat is underperforming.
I am getting 41 MPH and the dealer is saying I should get 55 out of it.
Not having any experiance with the subject I dont know what to expect.
I am thinking that the dealer may want to sell me something and wanted to know what I may expect.
I have done the comp. test and got 130 psi in each one.
Thank you

 

[sho3boater]

Re: What speed Can I go with Nitor SF185

I had an old checkmate 17 open bow with no pad, a 930lb hull and it has quite a bit of room in it. Had a old 1500 inline which is about 115 prop hp. With a laser2 20p it ran 6k rpm and that calculated to 50mph in my pre-gps days. The motor was raised 2" on the transom, I had to use lots of trim to get that speed. It needed a jack/setback. Also tried a stock 21p alum on it and it ran the same speed to rpm at lower speeds, but I could hardly trim much beyond level and the stock prop blew out so it didn't go that fast with the bow down. Stock prop would have needed the motor lowered back down to work right. My brand new speedo showed around 55mph or better, +5mph is typical for boats. The previous owner said it should run 60mph, it is obvious to me his old speedo was more generous. I tried at least a half dozen props on it, hardly anything in the boat, no foam in that hull to be wet either. Only thing is newer hulls often have a pad that adds some speed but they might be heavier too.

Man I loved that prop, trim it up and it would start buzzing it was great. The rooster was about same height as top of motor. That prop is made to surface partially, and lifts the bow like crazy. You can run it as high as it will still lift your bow. It is not going to work well if it is buried in the water. Hope that helps.

 

[xxturbowesxx]

Re: What speed Can I go with Nitor SF185

Thank you for all your responses.
I ask the question due to being told that the boat is underperforming.
I am getting 41 MPH and the dealer is saying I should get 55 out of it.
Not having any experiance with the subject I dont know what to expect.
I am thinking that the dealer may want to sell me something and wanted to know what I may expect.
I have done the comp. test and got 130 psi in each one.
Thank you

That boat will not go 55mph with 120hp.. the speed you are getting seems pretty accurate. To push that boat to a actual speed of 55 you would need around 150-175hp. With your motor and a perfect setup I would expect around 45mph(plenty fast).

I had a 17.5ft procraft bass boat with a 150hp and it would barely run 55.

 

[hwsiii]

Re: What speed Can I go with Nitor SF185

Haikt, you first mistake was in burying the motor, reating as muh drag as you possibly an.

Welcome to Iboats prop forum and we will try to help you as much as we can but without more information no one can help you, and I will tell you I need more information than anyone else. But if you would like my help fill this form out and I will help you as much as I can, if you would prefer to not go to this much trouble there are other people who will gladly help you.

Iboats Boat and Motor Info

1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the maximum recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape a c ross the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a Tiny Tach for $ 50
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.


H