New prop + expected speed...?

[Fregata]

Hi!

We got a 14ft Shakespeare Clubman + Mercury 115hp inline6 1988. The org. prop is still on the motor, but I can`t se any numbers on it that indicates the diameter and pitch. Anyway, we are looking for a good steel prop that would let the Merc run 5800-6000 rpm.

What kind of prop, diameter and pitch should I use, and what speed is realistic (boat weight: 250kg + merc)...?

Anyone got a clue...?

 

[jerryjerry05]

Re: New prop + expected speed...?

Remove the prop and on one end read and post the #s.
What rpm's are you running now at wot?
With out that info it would be a guessing game and it would be a good chance it's wrong.
Load and capacity have a lot to do with speed.An overloaded boat won't perform as well.
Post the info and you'll get a better response.J

 

[Hydro Head]

Re: New prop + expected speed...?

Naa

 

[Robbabob]

Re: New prop + expected speed...?

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

 

[Fregata]

Re: New prop + expected speed...?

Thanks for your answers, guys!

When we bought the Shakespeare in september it had a Merc 60hp. We sold the 60hp and found this 115hp inline 6 sitting at a dealer, so we haven`t tried it on the Shakespeare yet. All I know is that the motor got the old original alu propeller, so we want to replace it with a new steel propeller that can bring us upp to the recommended WOT at 5800 rpm.

Maybe it`s best to do some testruns in the spring with the old propeller first...to se if the pitch should go up or down? First off all we need to get the motor mounted at the right hight, and I`m thinking of maybe getting a man. jackplate for the boat.

 

[Frank Acampora]

Re: New prop + expected speed...?

You can't know where you are going until you know from where you are starting. So: Yes, test runs are the first step.

That said, the 115 is a strong engine and, for example, on on a 15 foot vee bottom Glastron did 52 with two people. So: Correctly propped, you can reasonably expect more top speed on the 14 footer.

Here is a flat bottom 14 footer about the same weight as yours that does 55 with a 90 and 60 with a 125. Both engines turn about 5000-5500 with a 12 X 21 stainless cleaver prop. So, you definitely will not want to go less than 13 X 19. That will be your starting point.

CAUTION::: Unless your 14 footer was specifically built to handle that horsepower, you will most likely be overpowering it and will need to pay attention to reinforcing it. (What are the regulations and laws there in Norway?) You will also need to be very careful around other boats and wakes at the speeds your boat will attain. While I sometimes advocate use of high horsepower on small boats, I always recommend putting a LOT of thought into how to do it ---and please act responsibly.

 

[steelespike]

Re: New prop + expected speed...?

Jack plate is an excellent idea.Easy to fine tune the height and gets the motor in cleaner water.

 

[Hydro Head]

Naa

 

[Frank Acampora]

Re: New prop + expected speed...?

Hydro: That boat has had the transom raised 5 inches and plated with .080 hard aluminum. It is also tied into the splashwell with aluminum plating. The boat itself is highly modified to handle the power. It has fiberglass stringers, a new floor, extra cross members, the hull and deck are glued together, and the seat box is made from 2 X 4 lumber. you can see the battery mount, fire extinguisher and 15 gallon gas tank. Steering is upgraded to Teleflex cable--If I had the money, I would go hydraulic.

Here's a better photo of the boat at 55 MPH with a 90 Force. It now has a 125 and tops out at 60 with modifications planned to try for 65.

You will notice there is no traffic. I am in a part of the river not used by many and it is a weekday. YES---Schuylkill-- alias Sure-Kill river

I am close to you. Send me a PM and perhaps we can talk, perhaps someday if you want to see the boat you can come out here OR we could meet at the launch area just west of Belmont Ave (Gladwyn?) off the Sure-Kill Expy..

 

[Fregata]

New prop + expected speed...?

Thanks again, guys!

The Shakespeare Clubman`s infoplate indicates max. 85hp, but our transcom have been reinforced. Battery and 25 gallon fueltank have been relocated to the bow. Our boat is in a very good rebuld condition, and the Merc. as well. The safety of my two kids and my self are taken good care of, and we want the boat to run in a strong but safe way. Running at 50+ several times every day is not the goal here, but we want the setup to be as close to perfect as possible. I would like to go prox. 40 mph on 3/4 trottle and still have the extra power if we need it. These old inline6 must "strech their legs" and hit around 5800-6000rpm at WOT.

Maybe I can find a good steel prop with 21 pitch and a manual jackplate during the winter, and start the testing in the spring from there. A brand new tach and a water pressure gage is already mounted.


P.S. I`m not the only one here i Norway that got a Shake with 115hp.