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buying a prop need help
i am going to purchase a 23 pitch 17 diameter prop for my z235 davanti does that sound about right i have a 23 pitch 14 1/2 diameter and it is spinning the prop when i hammer down do u think this in fact would solve my problem, pushing more water with a bigger diameter
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Re: buying a prop need help
I'm not sure if i am reading this right but are you intending to go from a 14 1/2" diam prop to a 17" diameter prop? If so, do you have the clearance to run something that size and possibly more important is whether or not your outdrive is designed to handle the increased load of such a large diameter prop.
If you are looking for some more jump out of the hole you could look at a 21" pitch prop or possibly a 22" - 4 or 5 blade prop. All in, you need to keep your WOT rpm's within the recommended range for your motor. So if your range is 4400 - 4800rpm and you are running at say 4500 at WOT with the current prop then you could drop the pitch slightly and it would increase your rpms along with giving you more bite out of the hole. You do sacrifice some top speed though so everything is a trade-off somewhere..... |
Re: buying a prop need help
You'll want to increase or decrease your pitch, not the diameter of the prop.
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Re: buying a prop need help
OK. Now I'm confused (easy to do, I know). I thought going from 14.5" to 17" diameter was a bit of a stretch, but I did think that bumping up the diameter would help push more water and give more bite.
Or wouldn't keeping the same pitch and diameter but going to a 4 or 5 blade prop give more bite out of the hole? |
Re: buying a prop need help
Diameter is another trade off. Larger diameters provided larger surface area, but require more torque to spin them.
Like Mikey stated earlier, the general rule is you drop the pitch a bit when you go to more blades. |
Re: buying a prop need help
Check out " BBlades.com " Great info on props, John had mentioned that the company will send you props to try out for a small fee plus shipping and handling.
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Re: buying a prop need help
Looking at the pics of your boat it looks like you have a bravo1 drive is that correct? A bravo 1 or alpha will not allow for a 17"dia. prop. If it clears at all, it would be only by millimeters. Here is what you need to answer to select a prop.
First of all what is your max RPM with the prop you now have? How do you most often use the boat, water sports, cruising, heavy or lightly loaded, or top speed more important? No single prop will do the best of everything but some come close. I found that a rev-4 that puts you at the high upper limit of the RPM range is a very universal prop. The bravo-1 prop has more blade area and gives more stern lift so it reduces top end more and is more sluggish out of the hole. The mirage-plus 3-blade is better for top end and if you put holes in the vent system it is pretty good out of the hole (not as good as rev-4) but you will lose some fuel economy mid range cruising. If you have a local dealer he may let you try out some props. BBlades.com is the option I used. Good luck! |
Re: buying a prop need help
This is all good (and correct) info, but it sounds to me like all you need is a new hub. Your description makes it sound like the drive shaft is turning, but the prop isn't, right? Easy, cheap fix. Then we can analyze the size/pitch prop. I think a 14.5" X 23 is about right for that boat/engine combo. Don't spend the money on a new prop if it's just a worn hub.
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Re: buying a prop need help
Now that i go back and re-read the initial post i think Indy is right. It does seem like Lance is trying to say that his hub is spinning when he puts the throttle down hard. If that's the situation then yes, the hub is likely worn and you should be able to simply replace the hub rather than the prop.
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Re: buying a prop need help
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Good call Indy, especially if its a flo-torq hub. About $35 will fix it. |
Re: buying a prop need help
I have exactly the same boat (it is actually for sale). I have tried a number of props and have three excellent combinations depending on the application. The setup is a 5.7l merc and an alpha 1 drive. Max RPM is 4600 on the motor nameplate. Let me know you interested and I will get you the exact numbers. The aluminum I use as an all around "ski or loaded up with weight" prop is a 19P * 14 1/2". This turns on plane at 3200 RPM so it is a little tougher on gas. I also have a 21P * 14 1/2" for light loads and gas saving in aluminum. It spins around 2800 RPM on plane. You won't get on plane with 6 people and gear with that one. The best fit is an odd ball stainless from mercury and I believe it is a 19P * 15 1/4". It gets the best top end right at 4550 ish and 50 + MPH on a smooth day. It turns around 2900 - 3000 RPM on plane. Just not a great prop to run in unknown waters as the stainless won't give if you hit something and likely f@$ the outdrive. I have access to a lot of props through a friend and this is what I have found work the best.
The 23P * 14 1/2" sounds like too much unless you have a different motor or gearing in the outdrive. Let me know if you want the exact model #'s of props and I can look them up. Or you could buy my boat as the props come with it.:) |
Re: buying a prop need help
Oh and by the way I agree if you hit the throttle and the motor revs up like it is slipping or out of gear you have rounded off the hub kit that fits inside the prop and it is going to get worst until you just can't go anymore. 30 - 50 buck fix. That is what they are made to do if you run it into the bottom or hit something. If you take the prop off and the hub is metal and has splines than it is something else going on.
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Re: buying a prop need help
I also have a question about regarding a prop. I just took my boat out for the very first time today and for my motor i am supposed to keep it in the 4500 rpm range. At that rpm range i am running about 40mph and I only have the throttle about 3/4 of the way down. It still has alot of throttle let in her but it will run the rpms up way to high. Right now it has a 3 blade prop on it but i am unsure of the pitch and diameter. Do you have any suggestions for what i can put on or do to use the rest of the throttle that is left unused?
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Re: buying a prop need help
It sounds like you are under pitched with the prop you have, but you need to know its pitch.:confused: The prop should have the pitch stamped on it. If not, you need to barrow a prop of a known pitch and retest so you have a known starting point to work from.
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Re: buying a prop need help
4500 rpm at 3/4 throttle? hmmm....either you are underpitched or the tach isn't set correctly. First, access the backside of your tach and you will see a small dial which allows you to set the tach for the # of cylinders your engine has. Yours (obviously) is 6 so spin the dial a few times (but wait for Bob Barker to say "Come on down!") then set it on 6. :)
As for the prop it should be a 19" or better still a 21" pitch and the diameter & pitch is usually stamped on the backside of the prop around the hub. Some just have a model # stamped there so you have to look them up on the Merc site. If your tach is working correctly and you're still hitting those rpms at 3/4 throttle then the prop is likely a 17" or possibly a 19". At that point i would suggest finding a 21" prop and seeing where your rpms are at WOT. You want to keep your rpms at the upper end of the recommended range (4400-4800) at WOT for the best performance. You could move to a 20" pitch 4 blade prop also but the 21" - 3 blades are easier to find. Note though, there are always trade-offs when changing the prop pitch. Going higher in pitch results in lower rpms and increased top speed but at the cost of some low end 'grunt' and going lower in pitch has the opposite effects. The diameter shouldn't be an issue as it will be around 14" in this range. |
Re: buying a prop need help
I agree with the above comments. If you do find that it is a lessor pitch (17, 19) and you are missing out on that top speed don't get rid or trade your existing one right away. Someone may have put that on there for skiing or tubing as you will get a bunch more pull out of the hole with the less aggressive pitch. The only problem is if you have 1/4 throttle left once you get going, you will have to really watch that you do not over rev the motor. If the tach is right you can likely get that motor over 5000 RPM and that gets real hard on things for any extended period of time. Once you get flying on the water it is easy to lose track of the dash because you start to be more worried about what is coming at you and the bulge in your pants.
I keep two different props in the Davanti and swap them out depending on the day and activity. One is good on gas and has a little more top end speed and the other lets you get out of the hole and going faster. |
Re: buying a prop need help
Alright thanks i will check both and get back to you possibly later today with that info.
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Re: buying a prop need help
Mikey, what are you running on the 180? I have a 183 and I want to get a prop that is good for tubing and loaded operation.. Anyone have recommendations here? I am all ears:horns::horns:
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Re: buying a prop need help
Alright i took a look at my boat the tach gauge is set correctly i checked that out and my prop has a stamp of "191619P quicksilver" on it. So any more suggestions? Thanks for all the help and opinions guys.
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Re: buying a prop need help
22 empire: I'm running a 20" pitch 4 blade SS prop most of the time since we tend to do a fair bit of wakeboarding and just running between the islands north of Parry Sound. If i'm going on a longer cruise, say along the shoreline of Lake Ontario, i usually swap to a 21" 3 blade aluminum prop for the higher top end and better fuel economy.
Irace: that looks like a 19" pitch prop so i would suggest looking for either of the props i mentioned above. The 4 blade should lower your rpms by about 1-200 and the 21" prop should drop the rpms by 3-400. The 19" will work fine for wakeboarding & skiing, the 21" (either aluminum or SS) will work fine for cruising. The 20" is kind of a mix between the two. It also depends on how much $$ you can afford to spend. A SS prop will give slightly better performance than an aluminum prop but at a higher initial cost. |
Re: buying a prop need help
I have one in aluminum 13.75" 3 blade 21P. I can find out what there are worth and work you a deal if your interested. Where are you at?
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Re: buying a prop need help
I just saw this.. I am in Barrie, and I would be interested in a prop. I need to see if there is a spare in the boat when I pick it up on Saturday regardless...
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Re: buying a prop need help
Just to throw this out there because it happened on my bass boat! My prop was slipping and after some discussion and looking from a local prop guy (Old guy with lots of knowledge), all he did was put a lip on the backside of every blade which in turn caused the prop to catch more water, in return no slippage!
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Re: buying a prop need help
Yep, i've seen that work. That's why prop blades with more pronounced 'cupping' tend to perform better. You can go too far though.....
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Re: buying a prop need help
One more question about buying a prop. Do i need to take the prop off and determine how many splines there are or should it be universal for a set type of outdrive? And also when i order one does a hub come with it to match it?
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Re: buying a prop need help
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Re: buying a prop need help
Hi,
I have a 1993 2350Z with Merc 7.4 and Bavo 1, but unusaul outdrive lower with oil drain hole behind prop/ It had a 4 blade 15.25" dia 15" pitch prop. The max rpm is quoted at 4800 for the engine, but it will easily exceed this if I let it. Does this mean I need to go to higher pitch? I am relatively new to baits and am learning as I go. I forgot to mention that the boat also has the switchable option for through transom exhaust. Any advice is welcome. I guess I should also mention that I am in Utah and the altitude where we sail is usually around 5000 ft. Clive |
Re: buying a prop need help
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