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Posts: 742
Location: Grand Rapids MN | Curious if anyone has tried one of these style props on the Merc 4-strokes. I know Yamaha factory props are of this style so it got me thinking. In particular I was thinking of trying a Powertech SCD4 series prop. PT said it would work fine but would like a few more opinions if possible.
Thanks,
Mike |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
First question: What handling characteristics are you looking for out of your desired propeller?
The semi-cleaver propeller is primarily designed as more of a stern lifting propeller, but does not have much more to it than that. Some steel props have some tip cupping to help lift the bow as well.
Also saw you had that amita for sale on the Classifieds. You could tweak that prop with more rear edge cupping to get more stern lift if that is what you are looking for. Any good prop shop should be able to do that and it shouldn't be too expensive...
I'll help if I can...
Steve
Edited by VMS 9/28/2011 10:29 AM
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Posts: 742
Location: Grand Rapids MN | Steve, basically I would like to find a prop that would help my mid-range cruising. Something to keep the boat up and more grip for porpoise control or during rougher water. During trips with longer runs, LOTW, I would love to cut the speed back and save some gas. |
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Posts: 742
Location: Grand Rapids MN | Also, what are the trade off characteristics typical of SC props? Less efficient/ more slip? Etc
Thanks Steve |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
In many cases, going to a semi-cleaver propeller without any tip cupping will result in more slip. In the Yamaha stock steel (black stainless) they have a touch of tip cupping, which I actually ran for a while and liked it, although it lacked speed at the same RPM levels as the ballistic propeller I also carried. That was due to the extra slip created by the blade design and lack of any sort of rear edge cupping on the blade. A little rear edge cupping on that style prop would do even better, although the more rear edge cupping you have, the harder it is to lift the bow since the stern receives so much lifting, forcing the bow down.
If you are looking for mid range cruising without the porpoise, I feel a 4-blade design of some sort would be in order. in most cases, running 4 blades requires a drop in pitch by about 2 inches from what you might turn on a 3 blade prop due to the increased surface area in the water of the 4th blade.
In many cases, running at mid-range requires you to trim down a bit from what you might use at full throttle. The reason for this is the balance of the boat required vs the rpm level you are looking to run at. In many cases, your trim angle might be less than half the amount you use at full throttle. The goal overall is to get a boat that just floats along at midrange speeds.
The Amita 4 you have on the classifieds seems like it would be a fairly ideal prop unless it is over pitched and/or has too large of a diameter. If it is over pitched the porpoising would become an issue at various RPM levels since the power of the boat cannot overcome the extra grip the 4th blade provides. I noticed you mentioned you tried it just a few times.... what did you have on before you tried the amita and in what pitch and diameter?
Tough thing in all prop choices is finding the one that best suits your needs, which usually takes trying out various props of multiple designs. Usually there is going to be a compromise somewhere along the line be it in speed, handling, hole-shot, etc....all dependent on what you are looking to get your rig to do well. In the whole process, though, one prop will stand above the rest in what you are looking for. It is amazing when you dial it in... The boat will do everything you want it to do, and do it with ease.
Steve
Edited by VMS 9/28/2011 1:11 PM
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Posts: 742
Location: Grand Rapids MN | I currently have a Solas 3 blade 17 pitch. I also tried a 15 pitch which dramatically increased holeshot but dropped my speed 6-7 mph throughout the rpm range. The 4 blade acted identical to the 3 blade but a few more less mph. It did not provide any more stern lift. So far my rig doesn't always seem to follow conventional wisdom. That 19 pitch allowed me turn 6000 rpm lightly loaded at 45 mph but horrible holeshot. The 17 turns 6100 @ 41-42mph same loading with improved holeshot. I also ran a 17 Trophy prop. Ventilated on holeshot, big stern lift but slow speed and really bad steering torque. Ran 38 @ 6400.
Oh ya, that 4 blade Amita did not drop my rpm compared to the 3 and I actually experienced less trim capabilities.
Hope this helps some. I've been at a loss as to where next. |
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Posts: 742
Location: Grand Rapids MN | I experienced that porpoising at various rpm with the trophy. Even at various trim positions. Should I have tried a 19" pitch? Is that you were saying? |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
In many cases, going to a semi-cleaver propeller without any tip cupping will result in more slip. In the Yamaha stock steel (black stainless) they have a touch of tip cupping, which I actually ran for a while and liked it, although it lacked speed at the same RPM levels as the ballistic propeller I also carried. That was due to the extra slip created by the blade design.
If you are looking for mid range cruising without the porpoise, I feel a 4-blade design of some sort would be in order. in most cases, running 4 blades requires a drop in pitch by about 2 inches from what you might turn on a 3 blade prop due to the increased surface area in the water of the 4th blade.
In many cases, running at mid-range requires you to trim down a bit from what you might use at full throttle. The reason for this is the balance of the boat required vs the rpm level you are looking to run at. In many cases, your trim angle might be less than half the amount you use at full throttle. The goal overall is to get a boat that just floats along at midrange speeds.
The amita you have on the classifieds seems like it would be a fairly ideal prop unless it is over pitched. If it is over pitched the porpoising would become an issue at various RPM levels since the power of the boat cannot overcome the extra grip the 4th blade provides. I noticed you mentioned you tried it just a few times.... what did you have on before you tried the amita and in what pitch and diameter?
Tough thing in all prop choices is finding the one that best suits your needs. Usually there is going to be a compromise somewhere along the line be it in speed, handling, hole-shot, etc....all dependent on what you are looking to get your rig to do well.
Steve
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Posts: 3508
Location: Elk River, Minnesota | Hi Again,
With the trophy prop, were the vent holes plugged or wide open? If the holes were not plugged, that would explain the high ventilation on hole shot, and could potentially be an issue on full speed if the holes are so large as compared to your power band that the exhaust gasses might not be able to fully blow by the holes. If that happens to be the case, I might wager to say that is why you saw such high rpms and very slow speed.
The trophy prop is a great prop for overall lift along with bow trimming capabilities. Do you still have that prop to test more?
Also, where is the motor mounted on the transom? one hole up etc? Might be able to work with things there too... This sounds like it is one of those conundrums that can really challenge the mind.... We can find it, though...that I am sure of!!
Steve |
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Posts: 742
Location: Grand Rapids MN | The Vent holes were wide open and they are quite large. Now that you say that it makes sense for sure. The motor is all the way down (top hole) and the cav. Plate is level with the bottom of the "V" when trimmed all the way in. I have been meaning to try it a hole or two higher. I do not have the prop as I took it back to the dealer. I did like how much grip this prop had. I could trim almost twice as far out before it ventilated compared to any prop I've used. Wasn't required but I did it to find it's limits. I may have been able to help the steering torque issue by adjusting the trim tab but as is I literally had to hang on one side of the steering wheel. No antifeedback unfortunately.
I appreciate the help Steve. After dropping some coin on the new motor I would like to get the most out of it. Maybe I can find a demo prop and play around again.
Edited by Targa01 9/29/2011 1:45 AM
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
I would bet if you could find a demo trophy prop that has different size vent plugs to try, you could really dial your motor in. I would not be surprised if you could have vent holes around 1/4" in diameter and get decent performance and good hole shot. If you find another trophy, the smaller vent holes will reduce your rpms a bit, but it should hook up even better than before.
I have no doubt you could raise your motor up probably 2 holes without issue, and a good chance you could go as high as the motor allows. The higher height will add a little more slip to the prop, but steering torque should go down a bit, with an adjustment of a torque tab taking care of even more of it. When you trim up, the torque should go down significantly and be pretty free when on plane.
We'll get it working... 
Steve |
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Posts: 742
Location: Grand Rapids MN | Well Steve I wasn't able to find a Trophy for a reasonable price but I did pick up a Powertech RXB4 in a 17 pitch at a good price to give a shot. I will still go up the 2 holes to start with. I think that's almost a must to do.
Have you had any personal experience with this prop? After some net surfing it seems to have a decent following with good reviews.
I'll let you know how things go when I get it installed and motor height adjusted.
Thanks for the help man!
Edited by Targa01 10/7/2011 11:07 PM
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
Unfortunately, I don't have any experience with that prop. If the price was decent, never hurts to try it out... Definitely interested in hearing how it goes with testing...
Steve |
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Posts: 742
Location: Grand Rapids MN | Well I received my prop and installed it today. I decided to try it as is before I raise it up 2 holes. It was really windy but here's my first impression of the prop.
It was difficult to tell if there was improvement in hole shot because it felt so close to my old prop. It may have a slight edge. Bow rise was about the same as well which was never really a problem so were good there. I tried to look at the splash line the best I could to determine if I was getting any more lift from the prop. It did not seem to provide much lift at cruising in comparison but at wide open throttle and trimmed out to the same level as my 3 blade the splash line was further back. Again I think there was improvement but was difficult by the seat of the pants testing. Plus I went to a short lake so it made even more difficult to get a good feel.
There was a lot more grip as far as cornering. It actually was scary how sharp the boat would turn now. I could also slow down and hold plan better (down to 3600rpm but it begins to lug some) so I'm going in the right direction.
here's a few performance specs.
27.7 @ 4200
31.7 @ 4800
33 @ 5000
40.5 @ 6000
I was glad to see that this prop still maintained good speeds. Almost identical to my 3 blade but a touch better in the mid-rpm range. Which I guess tells me that I must be getting some lift. Even though it was really similar to my current prop I am excited by the potential. I know this prop will react better to raising my motor than my Solas 3 Blade. Torque steer was not bad at all and once trimmed out it almost went away. I assume once I raise the motor that will take out a little more and then I can fine tune with the trim tab from there.
The prop does not have any vent holes and on the PT website they recommend 5/16" port. After I raise the motor and see how it performs maybe this would be another option to get an even better hole shot.
So what do you think so far Steve? Heading in the right direction maybe. |
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Posts: 742
Location: Grand Rapids MN | Some motor height pics for ya to reference. Boat has a 20 degree deadrise at the transom. Motor is all the way down.
(motor height back view resize.jpg)
(motor height resize.jpg)
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 motor height back view resize.jpg (43KB - 259 downloads)
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Posts: 3508
Location: Elk River, Minnesota | hiya!!
sounds like it is doing exactly as you had hoped!! That is great news!! No doubt I think you could move the motor up a couple of holes. It is definitely set down...I would bet your anti cavitation plate is in the water. I would bet if you move the motor up 2 holes, the plate will be out of the water at planing speeds with the only difference in handling being you might have to trim down just a touch since you will have a little more slip in the prop at a higher mounting position. worst case is you end up dropping it back down a hole...but I am betting you won't need to. You will definitely gain at the top end as well, and you might find bow rise on hole-shot might be less too..
Glad to hear things are going in the right direction...that is great news!!
Steve |
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Posts: 742
Location: Grand Rapids MN | I had the wife look at the cav. plate earlier this season to see where it was while on plan and she said there was just a little light spray over the plate. This was WOT and trimmed out to where I get my best speed without ventilating but as soon as I let off just a little it had increased water over the top. So you're right that this motor needs to come up.
Hopefully tomorrow I can get a good feel for the changes.
Thanks Steve... |
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Posts: 742
Location: Grand Rapids MN | Well I moved my motor up two holes and tried it out today. Again it was windy with a chop but I was able to find some cleaner water to test in.
Hole shot- there was a little less bow rise or it didn't stay up as long. Stern seem to lift a little quicker. Acceleration didn't change or didn't seem to. Kind if like the prop wouldnt spool up faster. I'm assuming getting it ported could help with that.
Ride - the ride improved especially at lower speeds compared to the 3 blade and a little over the lower motor mount. I could cut back to 3600rpm and still keep on plan and not porpoise. I even ran slower in the big waves and it did not porpoise and ran a smoother. It was a light load and I have yet to try it out with a heavier load yet. That will be the true test as my other props "weakness" would really show up then.
Performance - I actually lost anywhere from 1-3mph but it still pulled itself up to 40.5mph@6100. At 4600 it ran 27.7. So the lower the rpm seem to have a little more loss.
So I'm thinking I have to go back down one hole. The prop would also blow out a little on turns with any trim. And these were not as tight as yesterday's testing. Over all I'm thinking this prop will meet my needs. Adding an extra blade, more cupping, and even durability with SS without loosing speed isn't to bad and should help when I finally load the boat down. Plus scoring the prop for $150 shipped didn't feel to bad either.
So tonight the motor will come down one hole and back out to the lake tomorrow for testing.... And a little trolling! |
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