Turning Point Exhaust Flow

[Hydro Mark]

I just received my new Turning Point Hustler prop from Iboats. One of the features they tout is that the exhaust ports in the prop are opened up for increased horsepower and that was one reason I chose TP. My 1968 Mercury 1250 125hp 2-stroke came stock with an open exhaust (no exhaust tube). So I wanted to make sure I didn't compromise that design by choking it at the prop.

I was surprised that the TP prop had thick, straight, blunt hub ribs the whole length and fairly narrow exhaust ports. My Mercury prop has helical ribs and they are tapered on the leading and trailing edges as well as not going the whole length of the hub. The ports are larger as well. The hub center is also tapered.

Should I not test it and return it for a mercury? Or am I placing too much importance on it?

It seems to me that if TP is touting it, it must be an issue, but the mercury prop clearly flows better by design.

Thanks,
Mark

 

[steelespike]

Re: Turning Point Exhaust Flow

Not sure what you mean "Open exhaust no exhaust tube" The prop vents only enhances the hole shot the exhaust gasses
go out the vents during hole shot allowing the motor to rev easier thus reaching its horsepower range quicker. The vents don't
affect top speed as the gasses no longer vent at speed.Don't worry about the thru hub differences.

 

[Frank Acampora]

Re: Turning Point Exhaust Flow

Mark: That is a VERY DIFFICULT thing to answer: Exhaust flow and prop design are very esoteric fields. We here on the forum while well versed, simply do not have the education and equipment to cover everything. We make some very good educated recommendations most of the time.

As far as exhaust flow: You would expect that the larger and more free flowing the exhaust passages, the more horsepower an engine would develop. BUT, when Mercury redesigned Force mid and lower units, they severely restricted the exhaust downtube size and went to thru-hub exhaust. These engines make more useful horsepower than their equivalent predecessors. It seems counter-intuitive yet it works.

SO: You are basically taking what amounts to a small gamble with your Hustler prop. What you spent for the prop amounts to a couple of day's expense on the water so if it does not perform up to expectations, you are not out a lot of money and you still have a spare. At this point, the final choice as to return it unused or try it simply falls on your gut feeling. How aggravated will you feel if you use the prop and it doesn't perform up to your expectations? Would you accept it as a learning experience?

Remember ALL advertising contains some "Salesman Hype." Advertising's purpose is to get you to buy the product. So again, if it does not perform as advertised, complain bitterly and persistently but respectfully to the company and see if they would do something for you.

 

[Hydro Mark]

Re: Turning Point Exhaust Flow

Thanks guys.

steelspike: My motor did not come with the exhaust tube, or "tuner" as some call it, between the powerhead and LU. I tried to install one, but it won't fit the drive shaft housing.

Frank: That's interesting about the newer Mercury OB's having a tighter exhaust. I'm actually going to try to install an exhaust tube at some point, but it looks like I need a different drive shaft housing. I believe I will pick up more low/mid-range. So it looks like I'm on the right track.

Unfortunately, I won't be able to compare because my new prop is a different pitch. But in light of what Frank said, I think I will keep it and try it out.

Thanks again,

Mark

 

[H20Rat]

Re: Turning Point Exhaust Flow

Opening up a 2 stroke exhaust is the easiest way to LOOSE power! 2 stroke exhausts are very carefully tuned components of the engine, and play a huge part in clearing out cylinder gases and sucking in a new charge. Minor changes that seem to make sense are often very counter productive.

If you truly are making it breathe better, you also need to make carb changes, otherwise it will burn down from running lean.