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Prop questions for chaparral

bradscott48

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Hi guys new to the site and fairly new to boating. I have a 2006 chaparral sunesta 236 with the volvo penta 5.7 gi-e and duo prop outdrive with f5 props.
In late February we launched from site 6 for the first time. As we returned to the launch ramp there was a guy fishing right on top of the hazard buoy. As I crossed over the rock I noticed it. I. Cut the engine but couldnt get the prop up fast enough. Did minor bends to both props, they are fixed now.
So... I bought a set of hill marine 4x4 signature props. The boat rides amazing. It planes out of the water so much higher.... but I can only run 45 mph at wot wich is now 4800 rpm vs 55 mph at 5000 rpm with the f5s. Is this bad for the engine? Is there anything I can do to get my top speed back?
 

FreeBird236

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Hi guys new to the site and fairly new to boating. I have a 2006 chaparral sunesta 236 with the volvo penta 5.7 gi-e and duo prop outdrive with f5 props.
In late February we launched from site 6 for the first time. As we returned to the launch ramp there was a guy fishing right on top of the hazard buoy. As I crossed over the rock I noticed it. I. Cut the engine but couldnt get the prop up fast enough. Did minor bends to both props, they are fixed now.
So... I bought a set of hill marine 4x4 signature props. The boat rides amazing. It planes out of the water so much higher.... but I can only run 45 mph at wot wich is now 4800 rpm vs 55 mph at 5000 rpm with the f5s. Is this bad for the engine? Is there anything I can do to get my top speed back?

Welcome to RDP, sorry no one responded to you, most of the action is in the lounge. I don't know to much about the Dou-prop, but it sounds like they are too big, because you lost rpm, and yes if you can't achieve redline at WOT you may be lugging the engine, which isn't good on the engine.

On the other hand the fact that you plan faster makes it sound like they're are smaller props. Also dropping 10 mph seems like a lot for 200 rpms.

If the original props were matched to the boat by Chaparral and Volvo they'll be pretty hard to beat.

Hopefully someone that knows duo props will jump in. If not put this question in the lounge. Good luck:thumbsup


Edit.
I did some checking, all the hill duo props are called 4x4 and they go from f3 to f6. If you didn't buy f5 this might be the problem, if you did, then the specs on the Hill are different enough to cause this change.
 

Deano

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I've had a dual prop in the past and know they are more finicky than a single prop when it comes to prop selection. Your mph vs rpm is substantial. The difference between the two is enough to know the props are not right. Did you have the same load on the boat for comparison?
Contact Hill (or someone else). They will tweek those props until they work for you.
 

Trash

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Where does your mph data come from? GPS or in dash speedo. We cannot accurately answer your question unless the speed is accurate and we'd need the outdrive ratio.

I suggest GPS (good hand held) for speed accuracy and consistency.
 

bradscott48

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Where does your mph data come from? GPS or in dash speedo. We cannot accurately answer your question unless the speed is accurate and we'd need the outdrive ratio.

I suggest GPS (good hand held) for speed accuracy and consistency.
Yeah.... so I'm not trusting my factory tach or speedometer. I put the f5s back on on speedo says 48 GPS on my phone says 52. I'm going to be on the water all week so I'll be able to switch them back and forth for comparison.
 

BUDMAN

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What was your top speed before? I've got the same set up on my chaparral and run the same speeds and rpm's you mentioned in the first post. Max speed I've ever seen out of our boat was 50-55 @6500 rpm, and that was hammer down full throttle and really pushing it.
 

Trash

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What was your top speed before? I've got the same set up on my chaparral and run the same speeds and rpm's you mentioned in the first post. Max speed I've ever seen out of our boat was 50-55 @6500 rpm, and that was hammer down full throttle and really pushing it.

6500 RPM? With what motor, prop and drive ratio?
 

Trash

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Yeah.... so I'm not trusting my factory tach or speedometer. I put the f5s back on on speedo says 48 GPS on my phone says 52. I'm going to be on the water all week so I'll be able to switch them back and forth for comparison.

Tach should be fine. Ditch the in dash speedo values.

Get tach readings from in gear idle to WOT at 200 or 250 rpm increments and a GPS speed reading at each of those data points. Do this with both sets of props. Trim each set the same or for optimum performance at each set point.

Get back with that data and the out drive ratio along with any other observations (i.e. great hole shot, motor was laboring, pinned off the rev limiter etc).

Once we get a valid set of data the collective brain trust can offer advice.
 
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