I wanna go faster

[Harleyguy]

I have a 1994 four winns freedom 170 OMC 3.0 GL cobra wirh a 14.5 x 19 prop and the boat trimed out w/2 people only goes 35mph WOT @ 4000rpms.. If the prop is changed to a 17 or 21 will it go faster

 

[DavidD]

Re: I wanna go faster

21 should be for higher top end but a 17 should give you more RPM and a faster hole shot. 19 is the best middle of the road.

 

[Don S]

Re: I wanna go faster

Moving to Prop topics and questions.

 

[soler]

Re: I wanna go faster

I wanna go faster

ummm....give it more gas?

JK. The higher the number, the fast you'll go. It will just be a pig getting up on plane. Think of it as a gear. The smaller the number, the lower the gear, sort of. To get out of the water fast and have a higher top speed, you need more power (torque) so you can put a higer pitch prop on for top end, but the torque will get you out of the water. Of course, that involves engine work and stuff.

SOLER

 

[Harleyguy]

Re: I wanna go faster

Ive replaced the head and intake manifold on this boat so wrenchin...Im not scared of. I have a manual and iboats.com so I know I will go faster ... So how do I make it faster? And what r the 14.5 x 19 #s represent? What is pitch and what is the other?

 

[Maclin]

Re: I wanna go faster

The first number is the diameter of the prop. The second number is the pitch. Pitch represents how far in inches the propeller would move thru a solid medium like styrofoam. The higher the number the farther it would move with one turn. The higher pitch props also load the engine more during acceleration from a deadstop.

Sometimes the same or even slightly higher top speed can be realized from a lower pitched prop if the engine is not reaching full RPM with the current prop at wide open throttle. The main thing is to use a prop that gets the engine to top rpm and no higher at wide open throttle with light load, that way it will not have the potential to over-rev.

With your situation it may be worth trying a 17 pitch prop to see if the top rpm can be reached at light load. The acceleration from a deadstop will improve, and if the engine stays within the top rpm range then that is the best for your boat.

 

[Bondo]

Re: I wanna go faster

w/2 people only goes 35mph WOT @ 4000rpms..

Ayuh,.....

You're already Lugging the motor,....
A Bigger prop will Not move you faster,.. It's Already run out of HP...

You Should be seeing 4200/ 4800rpms at WOT....

 

[steelespike]

Re: I wanna go faster

Lugging the motor is bad could lead to premature failure.you need to be in that 4,200 to 4,800 range.
If you are sure the motor is in good shape and properly tuned and the tach is accurate.you could try a 17" pitch stainless prop.In prop size diameter is the first number second is pitch.Diameter is the product of the prop design
prop will have correct diameter for your application.
Is your speed by GPS?

 

[Harleyguy]

Re: I wanna go faster

I am using the speedo on the dash. I don't have a fish finder w/ speed on it. I am feeling that the 17 may raise the rpms to the 4200 range. I am also using the tach in the dash to.. The timing is set, and new plugs, wires, dist, and rotor are all new. I replaced the Head and Intake/exhaust manifold. all the valves are adjusted and it runs real smooth. But I'm the 3rd owner of this boat and when I tore into it I found that they used a merc 3.0 head with larger ports and a pretty bad match up but it did run and sounded good? needless to say it has all the correct pieces now. I didn't mess with the carb at all I was thinking maybe that would help but Ive never tuned a carb its a 1994 holly 2 barrel carb. Thanks for all the input so far you guys ROCK..

 

[fishdog4449]

Re: I wanna go faster

One thing at a time. You aren't going to get much more out of that motor because your already at only 4,000 wot. Which brings us to the second problem, you should be running 4,500 or so for the engine to run properly. Drop to a 17p and see what your numbers are. You won't lose very much speed because the engine will be turning faster.

 

[rndn]

Re: I wanna go faster

As stated several times you need to drop in pitch to get your motor running where it should. It will probably not increase your top end, but it will last longer. The best way to get more top speed is to buy a bigger engine or upgrade to a different boat. If you're not happy with the 4 cylinders performance, then there is nothing you can do that will help you out except replace it with the exception of adding a supercharger or turbocharger.