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Rob Turner

297 SSX Props

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I put my 2019 297 SSX in the water for the first time yesterday! I think I have a prop issue. I get the throttle to about 80% and the RPM is already maxing out at 5,000 and the speed is only about 40 MPH. It came with 26P dual props. The engine is 8.2L HO with Bravo 3 drive. Has anyone had similar experience with this combination? I am looking for recommendations on ways to get full throttle range and keep RPM under 5000. I was expecting to hit 50+ with this boat. Should I use 28P props, or try something different? Thanks!

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Rob,

I have a 08 276 SSX ( basically the same boat) w/ 496 Mag and I get 47 MPH w 26pitch t props so I do think you have something going on. 
What was you max speed /rpm last year?

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Something is not right. 26’s @ 5000 RPM should net you more than 40 mph. 
is your speed GPS? What is your drive ratio?

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You need to get the drive ratio,  to be sure.  Call a your local shop they can look up your serial numbers (engiine and drive) to see what should be on it.

26's might be a lttle small for that set-up. 

.

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Gear ratio is 2.2, and speed was on GPS (40mph). I have it narrowed to 2 possible problems. #1, these props aren't the right fit for this engine as geared at normal altitude, and I need to convert to 28P, or #2, the props are not tuned right and not giving enough bite. I may need to take them to a prop shop and have them cupped a bit to get more traction. Per the prop gods....

I think I will try tune the props first, then spend the money on new props if that doesn't solve my problem. 

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5000 rpm with a slip of 10% should be 50 mph with that set up. What were you doing with the trim during your WOT runs?

Something really wrong going on.

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Agree, no trim on this run, was the first time I had it out. Only got to 80% throttle. I'm looking into the prop balancing, then a prop tune, then new props, then last resort a gear change. I will report back. 

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23 hours ago, paulswagelock said:

5000 rpm with a slip of 10% should be 50 mph with that set up. What were you doing with the trim during your WOT runs?

Something really wrong going on.

Yup. The numbers do not make sense. Agree he should be at around 50 mph with that setup.

Any  chance the tach is off ? Set for 6 cylinders?

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9 hours ago, Rob Turner said:

Agree, no trim on this run, was the first time I had it out. Only got to 80% throttle. I'm looking into the prop balancing, then a prop tune, then new props, then last resort a gear change. I will report back. 

Before all of that, go run using trim to see what max speeds you can achieve at various rpm especially top end. Balancing won’t fix this issue.

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8 hours ago, paulswagelock said:

Before all of that, go run using trim to see what max speeds you can achieve at various rpm especially top end. Balancing won’t fix this issue.

Yes, good thought. I need to test it again now that I understand what's going on. 

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On ‎4‎/‎6‎/‎2020 at 9:49 PM, Rob Turner said:

Gear ratio is 2.2, and speed was on GPS (40mph). I have it narrowed to 2 possible problems. #1, these props aren't the right fit for this engine as geared at normal altitude, and I need to convert to 28P, or #2, the props are not tuned right and not giving enough bite. I may need to take them to a prop shop and have them cupped a bit to get more traction. Per the prop gods....

I had the same issue 2 years ago.  The Signature 260 is slightly smaller but about the same weight.  My problem ended up being a bad coil on one of the cylinders with no engine alerts.  Might want to make sure your firing on all cylinders before you drop a herd of deer on new props.

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That doesn't sound right.  Our 284 Sunesta has the 496 Mag HO with 26p props and it hit 50 with 3 on board and 100 gallons of fuel at 5125 rpms just yesterday.  Our boats should be pretty similar in weight and size.  I do have the 2.00 bravo 3 ratio and noticed you have the 2.20 so that might be the difference.  

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The drive ratio would account for a 10% variation. 

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On 4/13/2020 at 11:07 AM, Stretch79 said:

That doesn't sound right.  Our 284 Sunesta has the 496 Mag HO with 26p props and it hit 50 with 3 on board and 100 gallons of fuel at 5125 rpms just yesterday.  Our boats should be pretty similar in weight and size.  I do have the 2.00 bravo 3 ratio and noticed you have the 2.20 so that might be the difference.  

Thanks for the info! I have purchased Hill Marine 28P props. They are on the way. I will report back once I got them installed and let everyone know the outcome. 

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On ‎4‎/‎25‎/‎2020 at 7:39 AM, Rob Turner said:

Thanks for the info! I have purchased Hill Marine 28P props. They are on the way. I will report back once I got them installed and let everyone know the outcome. 

So for the smart people on the forum help me understand this.  I picked up the new 2019 Chaparral 297 SSX yesterday.  Got it out on Lake Michigan with about a 1 foot chop from high winds.  Before we put it in the water I made sure to look at the props when we were launching it. Right there on the side of the prop it said 22.5 P.  I'm assuming that is the pitch?!?!? Hole shot was fantastic, was at 30 MPH in no time and with the heavy chop I saw 45MPH and didn't quite open it up completely.  I was alone and didn't want to mess around with the water temperature at 48 degrees.  One person and 100 gallons of gas.  I don't pretend to know a lot about how prop pitch (or anything else for that matter) and I could have looked at the wrong number?  It doesn't make sense to me but I'm sure I saw 22.5P on that prop but this thread is talking about higher pitches of 26 and 28.

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What motors? What drive ratio? 

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On ‎5‎/‎2‎/‎2020 at 3:36 PM, brick said:

What motors? What drive ratio? 

8.2L 380 hp Bravo 3x  I don't know what the drive ratio is.

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Ok, I was able to get out and run my new props this weekend. Huge difference. As a disclaimer, it's highly unlikely that anyone is going to have the same set up as I do. I have 8.2L HO 430 HP, with 2.2 gear ratio in Bravo 3 outdrive (I would guess most everyone else comes stock with 2.0 gear ratio). You can call Mercury and give them your engine or hull number and they can tell you what your boat is. This was custom ordered for higher elevation. I brought it back down to 700 ft, therefore needed a change.  I started with Merc 26P 4x3 props, and converted to Hill Marine (Signature) 4x4 props. This is not a completely fair comparison to justify the Hill Marine props because I went up in pitch. However, the results speak for themselves. I was hitting the rev limiter at 5000 RPM on the 26P props at 85% throttle, so I need to drop RPM by 300 or so, going up to the 28P dropped the RPM and let me use full throttle. With the new props, I hit 52 MPH with 2 people on board and nearly 100 gallons of gas in the tank. The real sweet spot is around 3000 RPM, very efficient fuel burn (10% better). Also, I was also able to plane much slower, at 16.5 MPH, this is a big seller for some people. But you will see that it's not more fuel efficient to do so. The hole shot is less with 28P for sure. The other props really got me out of the water fast, but at the end of the day, I love the 4x4 props. I use this as a wakeboarding boat, and the lesser hole shot actually helps me not rip the rope out of my 9 year olds hands when we start. Also, I mostly cruise at 3000 RPM, so this is the right solution for me. I hope this helps, if you have any questions, let me know. I am now a prop professional! LOL

image.png.07c42987945af871f1d3dd9574a6e300.png

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On 5/4/2020 at 9:07 AM, Senior said:

8.2L 380 hp Bravo 3x  I don't know what the drive ratio is.

Look at the Merc sticker near the top of the drive. You will see serial number and drive ratio stamped on it

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