---

I have a 1990 18 Outrage with twin Yamaha 70 hp also 1990. I think red-line is 5500 rpm. With my original Yamaha stainless 13 1/4 x 17 props I red-lined about 6,000 rpm. So I bought 2 new Stiletto Advantage props 13 1/4 x 19 stainless.

Here are the results.

Yamaha prop cruising at 4,100 rpm went about 24 mph
Stiletto cruising at 3,300 rpm went about 25 mph

Yamaha prop WOT is 6,000 RPM about 38.5 mph
Stiletto prop WOT is 4,800 RPM about 40.5 mph

At 40.5 mph, the boat doesn't feel that stable.

Does this sound about right? I'm thinking maybe I should have gotten 13 1/4 x 17 Stilettos

At cruising with Stilettos it feels like motor is working harder, but I don't know.

My starboard side of dual control seems to not hold so well and the engine gradually looses rpm -- is there a way to tighten control?

Thanks.

---

Have you read this article?
http://www.whalercentral.com/articles...icle_id=35

The redline or WOT RPM's recommended by the manufacturer never changes... It is 6,000 RPM's in this case but check your manual to be sure.
You want to be right at 6k RPM's at WOT.....

It sounds like the Yamaha 17 pitch props were just right.

---

I think the new current model Yamaha 70hp motors are 6K, and that the older 1990 year ones were 5,500.

---

OK...

If that's what the manual says..
Then you want to be around 5500 RPM's at WOT....
What is the bottom line on the RPM's at WOT?
Most range from 4500 RPM to 5500 RPM
or 5000 to 6000.....

You could still try other brands of 17 pitch props as the 19 pitch Stilettos seem to be at the bottom of the range at 4800.
You would be working that engine too hard with a normal load in the boat.

---

Maybe Stiletto 17 pitch would be better. But I don't know if they would take the 19's back -- I used them today for 2 hours.

---

How about a 14X17?

---

John,

Props are purchased by PITCH and BRAND........

The engineer of a certain pitch prop determines the diameter for different motors.
You generally can't buy a 13x17 pitch prop or a 13 1/4x17 pitch prop from the same manufacturer for the same engine...

As consumers, we only need to be concerned about pitch...
Pitch, Pitch, Pitch....
After that, then whether it is bow lifting, cupped, double cupped, etc....

When buying a prop, we buy them by pitch or brand....
A 17 pitch will most likely perform different from a different manufacturer but again, we buy pitch....

Example:
Brand A = 13 1/4x17
Brand B = 13 3/4x17
Brand C = 14x17

Props above may have different qualities but they are all based on 17 pitch...
Brand C may be better or worse but really has nothing to do with the diameter, it has to do with pitch...

I see far too many people think they really have a choice in diameter....
Not really...

---

Gotcha Joe. I also have a Yamaha 200hp and the diameter, which is considerably different. I was thinking morer of his wot rpm's. Good information.

---

I just returned props. They will send me 13 1/4 x 17 to replace the 13 1/4 x 19. They said I should pick up 400 rpm. This would put me from 4800 to 5200 or closer to my desired 5500 WOT.

Also, I had ordered Stilettos but was sent Turbos. They tell me Turbos are the same thing. I have to pay a restocking fee, and shipping both ways.

The starboard side of my binnacle control slips a little. Is there some way to tighten this? It's a pain to have to constantly push it forward.

---

Dan,

Do you have Yamaha controls?
http://www.whalercentral.com/articles...icle_id=57

There is a friction adjustment behind the plastic cover on the bottom front of the control.

---

Yes, I have the Yamaha 704 Binnacle control. Thanks for info. I will remove cover and look for friction adjustment. This will definitely make boating more fun. Hope it works.

---

I'd always read that with twins it's good to be slightly under-propped in case you have to run on one engine for a while (vs having to swap to a lower pitch when that happens), helps ensure it isn't lugging. You're headed in the right direction, looking forward to hearing how the new props perform.

---

The Yamaha 70 has a 5500 RPM redline. 6000 RPM is way too much at WOT.

However, switching from a 17" Yamaha to a 19" Stiletto is a radical leap and brought your RPM down too much. As I have pointed out a thousand times, the Stiletto Advantage will perform like a prop from most manufactured with two more inches of pitch.

Going from a 17" Yamaha Painted Stainless Steel prop to the 19" Stiletto Advantage is like switching to a 21" Yamaha Painted Stainless Steel prop. You should do well with the 13-1/4" x 17" Stiletto Advantages (or Turbo 1s; they are the same prop with different decals, though the Turbo is their premium brand and costs more).

It is also important that your motor be mounted one or two holes up on the transom to take full advantage of the performance potential of the Stilettos/Turbos.

---

1990 18 Outrage. Twin 1989 70 hp Yamahas mounted 1 hole up.

Came with 13 1/4 x 17 Stainless Yam props. I think when I moved motors 1 hole up it increased rpms. I was WOT at 6,000, but needed to be 5,500 and lower.

Bought 2 Turbo prop 13 1/4 x 19 Stainless -- rpm dropped to 4,800 -- too low.

So I returned and got 2 Stilletto Advantage stainless 13 1/4 x 17 -- today I WOT at 5,300 top speed 40.6 measured by GPS

I cruise at 3,500 rpm and 28.5 mph With Yamaha props I was 4,100 and 24 mph.

So, I'm happy. I also adjusted throttle friction and now it stays where I put it, without being too tight. Be sure to use never seize on screws for plastic cover!

Anyone want to buy some nice 13 1/4 x 17 Yamaha props, let me know. If I hadn't raised the motors, they would've worked.

I also have a new fuel gauge in dessert tan for sale.

---

Joe, by combining my threads it doesn't make sense because I'm no longer asking for advice and I think it makes it more confusing to have to read through all the posts to get to the new info. Just saying.

---

Dan,

I wasn't sure.
I thought it brought closure to this thread.

Now we all know what you have done to optimize your boat/motor combination.
We also now know that your adjustment to the throttle friction works just fine.
Otherwise, this thread really would have been left unresolved in my thought.

Glad you got everything working the way you were looking for.