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Posts: 512
| The questions about this boat never ends! Sorry. I finally got to take the boat out, and i think it has the wrong prop on it, but not sure because ive never had this problem. It seems the boat peels out or slips sometimes, so im guessing this is cavitation and is being caused by the wrong size propeller? Didnt seem to get on plane very well either. The water splash was about half way up the boat, unless thats normal for this boat, i dont know. I thought when it was on plane most of the boat should be out of the water..
So.. once again, any thoughts would be appreciated..
seems this boat/trailer wasnt set up worth a crap!!
thanks
Dave |
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Posts: 32886
Location: Rhinelander, Wisconsin | Half way is good on that rig. Sounds like you may be over-revving or the motor is too high...take a picture of the motor and mount and post it and get the numbers off the prop. |
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Posts: 437
| The holeshots could be caused by a couple issues: motor not trimmed down all the, wrong prop or motor mounted too hign in the transom (which hole is it mounted in?) Once on plane does it "slip" when turning or going straight?
If you are working the trim correctly it is either wrong prop or motor mounting location. Changing the prop may gain you holeshot, but you will lose some top end (possibly). You just want to be careful to not overrev the motor on top.
You should be able to contact a dealer and they will be able to tell you optimum setup for that boat with your motor, as in hole location and prop. |
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Posts: 512
| I noticed it taking off, and again while turning..
its bolted in the second hole from the top.
Dave
Edited by Dave T. 8/23/2011 10:36 AM
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Posts: 512
| ya, it did get over 6000 rpm, think its supposed to be 4500-5500 wide open.
The prop says 13x19 on it, and here are two pics.
Dave
Edited by Dave T. 8/23/2011 11:42 AM
Attachments
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 motor 001 [].JPG (89KB - 151 downloads)
motor 002 [].JPG (106KB - 124 downloads)
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Posts: 437
| Operating RPM is 5000 to 6000 RPM so as long as you are under 6000 you should be OK.
Did you have the motor trimmed all the way down when trying to holeshot? The mounting location appears correct. |
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Posts: 512
| i believe it was all the way down, doesnt have a trim gauge unfortunately.
and it says operate between 4500 and 5500 full throttle in the manual..
Dave |
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Posts: 32886
Location: Rhinelander, Wisconsin | If you are hitting 6K with any load, you can go to a 14 or even 15. You should lose about 250 RPMs per number up in pitch. Height looks good. |
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Posts: 32886
Location: Rhinelander, Wisconsin | If you are hitting 6K with any load, you can go to a 14 or even 15. You should lose about 250 RPMs per number up in pitch. Height looks good. |
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Posts: 512
| ya, i think it might of went over 6 actually, will run it once more to double check..
Will changing props help with the cavitation/ventilation issues as well?
thanks Steve, did ya stick any skis up there yet??
Dave |
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Posts: 437
| Sorry Dave, I was looking at the 115 when I gave you those numbers. You are right with RPM ranges. It is 4500 to 5500. What seems odd to me is that you complain of holeshot and cavitation. With the RPMs you are pulling you should go up in prop to reduce the top end, but that would make your holeshot worse.
I bet your motor wasnt all the way down. Mine doesnt have a trim guage either, just keep trimming and the sound changes to a squeel when its all the way down. Then hammer on it out of hole, watch those RPMs all the way to top end. It should never hit the numbers you are talking about.
Here is a link to the suzuki specs for that motor (scroll down to 90, I looked at 115 first time).
http://suzukimarine.com/sr_07/df115-90/features/
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Posts: 512
| so 13 is the pitch number on my prop now? (13x19), nope, just looked it up. 19 is the pitch.. so now im confused. steve said run a 14 or 15, so go with a bigger diameter prop?
Dave
Edited by Dave T. 8/23/2011 1:44 PM
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Posts: 437
| I am not an expert by any means on props, but I think you have to stay with the 13, but you could go to a 20 or 21 pitch prop. This will reduce RPMs, but hurt your holeshot. I have a 150 suzuki and my prop is a 15 inch prop. Not saying your's is wrong, cuz I dont know for sure, all I could find was pitch. |
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Posts: 117
Location: Northwest Wisconsin | I had a problem with over revving this spring and changed from 18 pitch to a 21 pitch on a 75hp Mercury. I did lose 2mph top end but not enough to really notice a difference. |
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Posts: 512
| Now when you say over revving you are referring to the slipping/cavitation issue i spoke about earlier?
And what if you get a new prop, and it doesnt fix it, or you need an even higher pitch, then youre stuck with it and have to buy another prop?
Dave |
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Posts: 437
| Here is what I would do and what my dealer would do for me. They let me try the boat out with various props before buying them. I say take it to the water, make sure its trimmed all the way down and see how it reacts for holeshot. It shouldnt cavitate and no prop change will fix that.
I was searching online and I found some other guys with that motor that were running the same prop as you. I think it may be the right one, but you could go to a 21 to bring your RPMs down. If operating RPM is 5500 and you are over 6000 thats not good. |
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Posts: 512
| Different props wont help the cavitating? Then the slipping im feeling could be something else possibly??
i do need to get the rpms down, but i also want to solve the slipping problem as well, i didnt care for that at all
Dave |
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Posts: 32886
Location: Rhinelander, Wisconsin | Sorry, I thought the prop was a 13. What horsepower motor is this? it makes little sense you'd need a 20 pitch or 21 unless it's a higher HP small block. |
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Posts: 512
| Its a suzuki 90 h.p. four stroke..
Just never had a boat do this that i remember.. seems odd to me.
I hope its nothing major and it is cavitating/ventilation.
Dave |
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Posts: 3480
Location: Elk River, Minnesota | Hi Dave,
That motor will turn a pretty steep prop because the gear ratio is 2.59:1. I would suggest finding a good steel prop. What I would bet is happening is the prop is not pitched enough, or worse yet, the hub on the prop is spun out and not functioning. If the hub is spun, it might catch a little then it might not, but if you have been able to get up on plane, but not very fast, I would think the hub is fine. If the prop is under-pitched, it will be slow, and with your rig, you should be able to get the side-spray further back without issue and get more of the boat out of the water altogether.
That motor should have no problem turning a decent 13 x 21 steel prop and still get good hole shot and good top end. A demo prop program would be a great thing if you can find it, although many dealers require you make a purchase, so it can be a bit hit-and-miss...
The other option which I have utilized quite a bit is ebay... lots of props on there and some really great deals as well..
Steve
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Posts: 32886
Location: Rhinelander, Wisconsin | Ohhh, a Suzi. Different gear ratio. VMS is correct. |
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Posts: 512
| Yep, i ran it pretty fast so i dont think it is the hub, had it up over 40 m.p.h. before the speedometer stopped working.. thats another question i have, i couldnt find the sensor for the speedo, i found a small hole in the lower unit in front, is that the speedometer sensor?
I have never purchased a prop, so i will check ebay, and see what i can find..
Are props engine specific, or are they universal?
thanks a bunch again guys
Dave |
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Posts: 3480
Location: Elk River, Minnesota | Hi Dave,
Props are actually boat and motor specific in that no two boats with the same motor will act exactly the same way..so...finding the right prop for what you want your boat to do is a matter of trying different ones. Usually what happens after some testing of different props, one will stand out and perform the best for everything, including hole shot and top end, along with good handling. The right prop will allow the boat to just float along at cruising speed (not wide open) and handle without any issues.
Most larger motors have a tube that runs out of the lower unit (usually close to the front of the lower unit by the shift linkage if you can see it). There is a hole below the cavitation plate that it will go to (which is what you found), then that tube goes up to the speedometer. Most of the time, the speedometer set up to work via water pressure is not extremely accurate and can sometimes be quite a bit off...so a GPS will give you a more accurate reading on what is really going on.
Pretty big learning curve isn't it... 
Steve
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Posts: 512
| So the prop will be specifically for a suzuki DF90? Or will any 13x21 work on this motor?
And there is supposed to be a tube going into that hole i found? I hope not, cause its gone! or is the tube inside the motor? I dont understand why it stopped working, unless some weeds plugged it up maybe?
Ive had a lot of boats, but this one has been schooling me!
just found this parts list for the motor, and it calls for a 3x14x19 prop. just keeps getting weirder. why would it call for a 14, and what is the 3 for?. opps found it, 3 blades.. also has 17,21, and 23 as options..
heres the link to the parts page.. http://www.danssouthsidemarine.com/assets/layouts/main_layout/parts...
its on page 35, didnt realize it would load the whole book!
thanks Steve
Dave
Edited by Dave T. 8/23/2011 9:09 PM
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Posts: 3480
Location: Elk River, Minnesota | Hi Dave,
The 3 is for the number of blades, the 14 (first number) is the prop's diameter in inches, and the 19 (last number) is the prop's pitch in inches (theoretically, the prop would push the boat 19 inches in one full revolution, but the prop must slip so it is usually a little less than that)
The prop must match the hub for your particular engine. The diameter and pitch can change, along with blade design, which is what you get to play with when trying to find the correct prop for your particular rig. Your lower unit shaft will have a certain amount of splines which must match the hub of the prop in order for it to fit.
So... in quick review: the hub of the prop must have the same number of splines as the shaft in the lower unit (i.e suzuki specific for your motor size), the first number is the diameter, the last number is the pitch. Blade geometry/design plays a huge role in the function of the prop, so it must be considered in order to get the best prop for what you plan to use the boat for.
Questions are a good thing... helps the learning curve for you, and for many who are also following the thread.... So, ask away as you feel need...
Steve
Edited by VMS 8/23/2011 9:25 PM
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Posts: 512
| Thanks Steve, i appreciate it.
Well i wonder why i have a 13 inch diameter prop on there now, when the parts breakdown for that engine calls for a 14?
maybe that is part of the problem also?
Ill get this figured out someday!!!
thanks again, i just wanna drop the boat in and go fish!!
Dave |
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Posts: 3480
Location: Elk River, Minnesota | Hi Dave,
If the diameter is too small, the prop will spin more freely as well... 14 x 19 is just a standard size... If you go to the suzuki outboard website, you can download the different prop sizes that will fit your motor, but keep in mind these are just suzuki brand props. There are many aftermarket props out there that are designed to fit your motor as well...in fact, aftermarket props are in most cases cheaper than OEM props.
When I looked at the chart, a 14" diameter prop is what the majority of the props are with a 13-1/2 x 15 as the smallest size.
So..knowing the diameter should be around 14, I would say a 14 x 19 would be a good start... Your motor is going to have a bunch of power with the gear ratio...
Steve
Attachments
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propellers.pdf (177KB - 468 downloads)
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Posts: 512
| Thanks again Steve.
i was looking for that page!
Hopefully i can find a good aftermarket one..
im also going to put a hydro wing on it, i have on all my other motors,
and maybe that will help as well
Dave |
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Posts: 3480
Location: Elk River, Minnesota | Hi Dave,
With the right prop, the fin is not needed. In my humble opinion, a fin is a band-aide for an incorrect prop on the motor, and is primarily used when a boat is under-powered. Your boat is maxed out, so a fin will only slow you down. When the boat is on plane and set up correctly, the cavitation plate should actually be OUT of the water, so the fin would be doing nothing for you...
I am running a Johnson 90hp that is up a few inches off the transom, and no fin is needed...grabs like a son of a gun with the right prop on it.
Steve |
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Posts: 395
Location: NW WI | My .02...and random thoughts...
Dave - where do you live?
Before you start dropping $$ on props, somebody like a VMS or any knowledgeable guy should go visit Dave and take his rig for a ride and provide input from there. It sounds like you're throwing darts right now.
Where is your dealer in all of this? Do I recall that you bought the boat some distance away from you?
If the gear ratio on that motor makes so much torque, would you want to run a larger diameter prop and also a stainless steel prop? Start with a larger diameter then dial in the pitch from there?
VMS is right on the fin....don't do it. Spend the time to get this thing propped right. Is the boat maxxed out on HP?
Invest the $$ and have a trim gauge installed. IMO - no boat with trim/tilt should be without it.
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