Chaparral prop cavitation

[Doug Durako]

Re: Chaparral prop cavitation

The 5 blade will do what you want with a boat load of gear and people, but you will lose 5 or 6 mph at top speed (more blades, more grip at the low end, but more turbulance at wide open throttle).<br /><br />What you describe as a quick turn at max speed depends on the hull design, drive, and engine placement. You probably can only do that maneuver with a jet drive or a mid-engine rig once you pass 45 mph or so. Some of these guys out west with their mid-engine metal plate boats and jet drives can do donuts at 45 mph in about 6 inches of water.<br /><br />If I did what you describe at wide open throttle (63 mph) with my rig, I would kill everyone in the boat. In fact, Baja puts a warning in large letters right next to the steering wheel not to attempt any turns at max speed.

 

[Doug Durako]

Re: Chaparral prop cavitation

Richard---I use my Torque Shift prop for skiing, wakeboarding, and tubing. Search that topic on this board and you will get a ton of data.<br /><br />Basically, the TS starts at 13 pitch, and will pull three tubes, two adults on each, with 6 people in my boat and launch it with ease. At about 2800 rpm, the prop begins "shifting" and the blades move on a cam set until it reaches a max of about 26 pitch.<br /><br />I don't run the TS all the time because it does not give me the max speed I sometimes crave.<br /><br />Props are like fine women, you have to find the sweet spot for each one.

 

[Richard Petersen]

Re: Chaparral prop cavitation

I never realized there are so many props and gimmicks to prop performance. A really experienced prop person could do wonders. What does a Torque Shift cost new- used my size range. Thanks.Rich

 

[walleyehed]

Re: Chaparral prop cavitation

Before you spend a single dime on a prop, find 2 things..#1 remove your prop and find the numbers-they ARE there. #2, is there any transom mounted device such as a transducer, speed sensor, etc, mounted to the transom??????<br />

more blades, more grip at the low end, but more turbulance at wide open throttle).<br />

Wrong....more blades, more DRAG, less top end, more hole-shot is the only advantage of the 5-bld., on a stern-drive. The prop you have now quite surely has a problem.<br />If your boat is on a trailer, climb under and inspect the area of the hull in front of the drive...is there any gel-coat missing, any damage of some kind???<br />If a prop is cupped properly, it will not blow out trimmed full down. If the prop has been worked and had too much pitch, and someone with great wisdom tried to decrease the pitch thinking it will raise RPM, well, it will but for the wrong reasons, and things such as blow-out become common place.<br />We have to determine what is causing the problem before you band-aide it with a 500.00 patch.<br /><br />EDIT:

I did not get the best results from my Merc stainless 23-pitch, so I had them beat it back to a 22-pitch.<br />

I'm sorry dd, but this is a perfect example of what I'm saying. You NEVER remove pitch from a prop, it decreases effective use and lowers efficiency. ALWAYS error on the low side of pitch and have cup ADDED as needed to achieve desired RPM.<br />As for set-up, you want a normal load and 4800 RPM, not heavy or lite.

 

[Richard Petersen]

Re: Chaparral prop cavitation

The prop is stamped as 14 1/2 X 21---3 alum.-------------Bought boat new 2002, no groundings, has done this since day one.

 

[Richard Petersen]

Re: Chaparral prop cavitation

MFG. says they have a planing pad at the rear of the boat. How much vertical clearence should there be between the bottom of the pad and the top of the prop. Drive level to the keel or the pad ?

 

[walleyehed]

Re: Chaparral prop cavitation

The ant-ventilation plate should be level with the keel. Is there anything mounted on the back of the transom??<br />The pad would be level to the waters surface at top speed, which is also where the cav. plate on the out-drive should be.<br />The keel would not be lower than the pad.

 

[Richard Petersen]

Re: Chaparral prop cavitation

Factory option of the depth finder. If I remember, right side about 20" from centerline. Not sure if it goes thru.

 

[walleyehed]

Re: Chaparral prop cavitation

If it's 20" from the center-line, it's not an issue, especially when mounted inside...<br />Are there any dings, bends or chunks missing from the skeg????

 

[Richard Petersen]

Re: Chaparral prop cavitation

I have never had a need to look. The boat is power washed by a good yard and no mention of damage or even scratches comes up. However, I do not now know, if the bottom is still true after years of storage. This problem existed the first five rides new.

 

[walleyehed]

Re: Chaparral prop cavitation

That would lead me to believe an incorrect prop was installed, or something is causing a cavitation pocket that the prop is going through.<br />Have you checked for a spun hub??? this may have come up earlier...but usually they won't even plane-out.

 

[Doug Durako]

Re: Chaparral prop cavitation

Thanks, Walleyhead, now after four posts, you are back to where we started with Richard.<br /><br />You really should read the previous posts before responding.<br /><br />Also, drag creates turbulance and air at wide open throttle, which is why 5 blade props lose top end speed. You did not need to correct me as I said the same thing.

 

[walleyehed]

Re: Chaparral prop cavitation

ddboater, none of you asked any questions that one who tests hundreds of props a year would ask...<br />Turbulance creates ventilation, not drag. The top-end is lost because it requires more power to pull another blade-they are inefficient except in rare cases.<br />I would like to know the manufacture of the prop and whether it was new with the boat, or if a dealer put one on off the shelf that was a rebuild.<br />Factual data is the only correct testing procedure...we have got to have a base-line.<br />14-1/2X21 means ZERO to me. We don't know that it wasn't worked BEFORE he bought it.<br />Put a pitch gauge on your Laser and report back....it ain't a 22, but that's what it "says" it is.<br />ddboater, beings you are the resident expert, I'll leave this thread to you...I read all the posts above, and 2 of the guys got real close.

 

[walleyehed]

Re: Chaparral prop cavitation

Richard, what "I" am trying to help you understand is that the prop you have installed may have been wrong from day one. The Prop you have may not have the proper cup for the blade style and the weight of the boat-this is not uncommon.<br />We've got many boats Identicle to yours on Texoma, and we don't have any issues with these.<br />Keep in mind a dealer set-up isn't always the "correct" set-up...I see this all the time. Not all dealers are this way, but some don't understand the technical side of props or there intended use.<br />It is quite possible you may have to buy another prop, but the high-five isn't going to produce the numbers your boat is capable of.<br />I do know of a couple of props that will help considerably, but I will offer that advice if you request, as I don't want to start any fights with the rest of the crew-there's some good guys here, props just happen to be an item I have a great interest in and a little more knowledge of how they work.I have tested quite a few in and on many applications. <br />BTW, the picture of the prop with my post is a prop I have designed myself, and a Major prop performance manufacturer (Built by them) is helping me fine-tune the 3 prototypes I have. These are a lower bow-lifting design intended for high running heigths on Deep-V outboard applications.