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Posts: 279
| I have a 17ft v bottom boat with a 115hp optimax with a trophy plus 19p prop. Gps speed of 41-42@5400 rpms. With 2 people and decent load its 38-39@5200 rpms. With 3 people the holeshot is horribly slow. I carry a decent load all the time and was curious on a few things. Will at 17p of the same prop help with the holeshot and max rpms? Im not too concerned with what it will do with speed as I don't run full out usually.
Edited by ttrap 8/22/2012 1:54 PM
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Posts: 3514
Location: Elk River, Minnesota | Hiya,
to answer your questions: Yes and Yes. If you go down 2 inches in pitch, you should see a gain of about 400 RPMs on tope end, given you have the same overall diameter, which is still well below where it should be for that motor. Holeshot will be better as well, but as I see it from what you have stated for information, the prop you are running is way off, given the motor is running well overall.
To get closer to the rpm range I would say you need a combination of two things: lower pitch and maybe a smaller diameter. What boat are you running? And...have you had the tachometer checked at all? I would say the speed is close, but holeshot says a bunch too..
I'll help as much as I can.
Steve |
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Posts: 25
| Prop it more at 5850 wot by yourself light load full tank 17 pitch sounds better. Is your tach set correctly?
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Posts: 279
| Its a tuffy 1700. Was brand new when I bought it this year so should be okay on tach. |
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Posts: 279
| How do I know what the diameter is? Does that have to do with the #'s on the prop. Also there is the one in the for sale section how do I know if that will fit my motor?
Thanks guys |
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Posts: 3514
Location: Elk River, Minnesota | Hiya,
If you look on the back side of the hub or on the side of the hub there should be a stamp of some sort like 14 x 19 on it. The first number will be the diameter, the second, the pitch.
I would agree that if the boat was new and set up correctly the tach should be right, but it never hurts to get it checked a second time.
If you go back to the dealer where you got the rig, they might have a demo program to allow you to try different props on your rig. I'd be interested in seeing if they have some different ones to try, just to see what the boat can do with different blade designs, number of blades, etc.
I would be looking to find out if they have a 14 x 19 pitch tempest. Seeing as though you have a trophy plus in a 19 pitch, that extra blade is what is pulling your RPMs down dramatically. I bet that if you get a 19 pitch tempest on there you will be VERY happy with the result. And...depending on the RPM numbers with that, you might be able to move up to a 21 pitch and really get that boat moving. Either way, you will be much closer to optimum RPM with the 3 blade without much loss in handling, and the boat should be able to get up on plane much quicker as the tempest has different vent plugs to tailor the hole shot to your liking.
Steve
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Posts: 32958
Location: Rhinelander, Wisconsin | You need a 17 pitch if you are looking for hole shot with a heavy load. What's the WOT rpm on the 115 now? |
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Posts: 279
| Im looking for best overall performance. well wide out rpm is 5350 with just me and a decent load. With 2 people its 5250. And with 3 its about 5000. I like the way this prop drives the boat alot when its just me in there and its not bad with,a second person, but I always have a over loaded boat and at least 2 people total and am really just concerned with a better holeshot. I think the 17p is a good choice and there is a used one in the for sale. He said the #'s are 48-825930A46 17P. So I guess I need to find out if that will fit my motor? I need to know the diameter of my prop.
Edited by ttrap 8/22/2012 1:12 AM
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Posts: 3514
Location: Elk River, Minnesota | Now I'm confused...
in your first post you said 2 people was 4200 and you alone it was 4400. I was going off those numbers.
If it is in the 5300 to 5000 range, you then could drop to a 17 pitch and move the motor up a notch or two and get it running at the optimum range. you can also tailor the vent hole plugs there as well. open up the holes a tad to get rpms up higher before the prop bites the water on hole shot to help it get up on plane quicker.
Steve |
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Posts: 25
| Thats why i asked about the tach. With 10% slip with a 19 it puts him around 5100.
Do exactly what VMS said |
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Posts: 32958
Location: Rhinelander, Wisconsin | Do NOT move the motor up. You will have no end of cavitation issues. Your top RPM with a 17 will be 5600 if you are light load, which is OK. Your top end speed will lose about 2 MPH and your hole shot will improve quite a bit. This is a small hub stainless prop for a Merc 115, and most of those do not have the PVS. |
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Posts: 3514
Location: Elk River, Minnesota | Steve,
Do they make the tuffy boats with a higher transom than other manufacturers and build in a set-back on them as well?
Thanks
Steve |
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Posts: 279
| Okay yes i see that i messed up with my first post that should have been 5200rpm and 5400rpm. sorry now i see the confusion. Is there a issue with going to a 3 blade prop? And what would they do differently than the 4 blade?
thanks all
Edited by ttrap 8/22/2012 1:54 PM
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Posts: 3514
Location: Elk River, Minnesota | Hiya,
The 3 blade prop will allow you to go to a higher pitch in most cases as you don't have the extra friction of the 4th blade. What you give up in losing the 4th blade is handling for the most part, but speed is what you normally gain.
Some of the really heavy boats need the extra blade for the increased lift it provides. A great example of that is in the Ranger 690 series of boats where the gas tank was located more toward the bow of the boat. The 4th blade on the prop helped with bow and stern lift giving better performance and less slip.
No matter what you do with propping a boat, there will always be compromises that need to be made. Usually it is a balance desired by the driver for holeshot and handling vs speed.
Steve |
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Posts: 967
| Put a whale fin on the back it will help your hole shot on your tuffy.
It helped mine a ton. I also have a 4 blade 17p stainless prop on my tiller 90hp
I have a Tuffy 1890 osprey GT, I have 3 people and boat loaded down all the time and have no problem getting out of the hole with the whale fin. The guys at Quam's Motor sports in Stoughton had me do it, its been great
Good Luck,
Jeff Hanson |
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Posts: 68
| Like one these? http://www.cabelas.com/product/SE-Sport-300-Hydrofoil/699943.uts?Nt...
I put a Hydrofoil on my HydroStream with a Rude 150XP, and surprisingly noticed a difference. I was skeptical, but the guys at West Marine in Monona convinced me to try it and they were right. |
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Okay prop guru's