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Posts: 388
| I have a 2004 DF90 Suzuki on 1750 Crestliner Fishhawk. Have always ran stock aluminum propeller 14x19. Hole shot has been very good with this combo. When the prop was brand new, I could reach 40 mph (GPS) at 5600 rpm which is a little above the recommeded operating range for this motor (5000 to 5500 rpm). Motor is mounted on the center hole.
Over the years, I have shaved a little material off of this prop through normal wear and tear. RPM's will run up to 5800, top speed is down to about 38 - 38.5 mph. Hole shot remains very good. I have a newer spare aluminum prop but it tends to suck air / cavitate easily and is more finicky with trim angle.
I am considering a stainless prop this year. Have had recommendations to go to a 14x18 prop in stainless but was hoping to get some info from others who have made a switch on a similar combo. Suzuki's are a little tougher to size up due to unconventional gear ratio of 2.59:1. |
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Posts: 3504
Location: Elk River, Minnesota | Hiya,
I do not run a Suzuki but I would agree with a switch to 18 pitch. You will lose some RPM going steel, but dropping in pitch by an inch will increase the RPM back to the 5500 desired.
The other option you have is to stay in the same pitch, but reduce by 1/2" If Holeshot is nice with the prop you had running 19 pitch, staying in that pitch should be fine, but you will lose about 200 RPM. By decreasing the diameter, you can gain that back as well. you can expect about 100 RPM's for each 1/4" in diameter...so...going down by 1/2" will give you 200 back from the 200 rpm loss in changeover to steel.
A good steel prop will also have a bit more cupping on the trailing edge as well, so it will not flex as much, and the cupping will act much like another inch in pitch. In effect, a good 19 pitch steel prop with decent cupping will act more like 20, which is why I would suggest going down 1/2".
If you can, find a good prop shop/dealer in your area that has a demo program. Get 3 - 4 different props in pitch/diameter and head to the lake....make test runs checking and recording items like holeshot, top speed, and handling, bow lift and overall boat lift, trimming etc. One will stand out over the others in most, if not all areas.
If I were to make a suggestion, I would look at an older michigan rapture that has the XHS system in it (If you can find it...ebay being key). This will give you options since the hub is interchageable and can be made to fit your motor. Key issue here is getting the right hub diameter. All in all, I say go 13-1/2" x 19 with a good trailing edge cup. What I feel this would do for you is give you the RPM you need, maintain your overall holeshot, and increase your top end by a couple of MPH over your original stock aluminum. Depending on what you find in props, you might be able to tweek out more as well by lifting the motor higher on the transom, then increasing the diameter of the prop based upon the number of holes you move up. If you go up 1 or 2 holes, I would say increase diameter by 1/4".
Lots of variables, but with a little time invested, you can find a prop that works really well.
If you want to stay aluminum I would suggest a solas propeller. I was out last night and put on a solas alcup 3 on my 90hp yamaha and I think it performed almost just as well as my michigan ballistic propeller. It cornered better than my ballistic, and I only lost about 1/2mph in speed. I was very surprised at that with where my motor is mounted.
Steve |
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Posts: 388
| Update to above - Tried two different SS props this year.
14x18 was not enough prop for the motor. Motor would hit the rev limiter (6000 rpm) at about 37 mph.
14x20 seems just about perfect with the exception of the fact that the prop tends to break loose with too much throttle at once or with boat trimmed out. Have to keep the nose down a little more than I would like to prevent sucking air. Can get to 39 mph consistently with nose down and a little bit of torque on the steering wheel. Can get past 40 while making a moderate right hand turn (not sure what that means). This was a used prop bought on ebay and I am wondering if it needs a little fine tuning to make it less prone to sucking air. Would like to trim up a bit more and get the torque off and get a few more MPH out of this prop. Any advice? I did try adjusting the tab on the cavitation plate and this slowed me down about 1 mph. |
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Posts: 1094
Location: Hayward, WI | I run the same setup and best prop for all out speed I have found is a Mercury Trophy 21 pitch, but if loaded heavy it is a little too much. With heavy loads a 14x21 3 blade Turning Point Express SS worked very well or a 19 Trophy worked well also but was a little slower. The Trophy is a 4 blade and it really holds well in rough water and is very good at keeping the bow up.
Might want to try possibly lowering the motor one hole, it might help with the cavitation issue. |
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Posts: 388
| Thanks for the info. Motor is mounted in the center hole. Has worked pretty well for the stock aluminum prop unless I am cornering aggressively (have to trim down to do so without ventilating). Have always like the way the boat gets up despite the Suzuki being a heavy motor (400#).
Not sure if the prop itself has some tendencies to suck air (ventilation). Believe that this was a reworked prop and since posting last have found some info relative to ventilation on reworks... |
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Posts: 3504
Location: Elk River, Minnesota | hiya,
I would say you might be able to have the prop tweeked a bit with some cupping added to the tips and the trailing edge of the prop. What this will do is help the prop stay hooked up with the water, and the lowered RPM might be able to be offset by a higher motor setting. If you have not been able to trim up to optimum, you might be low on rpms as it sits now, so the extra cup might get you up there....my gut says, though that a move up of 1 hole after cupping would be close to ideal (again...not seeing the boat run...so tongue in cheek on this for the most part).
What prop did you find on ebay? would be interesting to hear brand and model as that can be a good indicator of what the prop is like and what could potentially be done with it.
Steve |
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Posts: 388
| This is a Suzuki prop, 3 blade 14x20. Although I cannot see any kind of visual defect, I suspect that it was reworked. Bought from a seller that deals a bunch of props and does the rework. Feedback was good so I would think that the prop could be tweaked as you suggest.
If I knew that I could easily adjust the height of the motor I would attempt it but am reluctant to do this myself. Not sure how much more I could trim up with my standard aluminum setup if I did this and never tried based on how well this boat gets up on plane - something that the dealer that I bought the boat from when new attributed to the way that they set up the 1750 fishhawks.
Any suggestions on who can do the cupping work? |
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Posts: 3504
Location: Elk River, Minnesota | DAH propeller. Lots of good feedback from the work done there.
As for raising or lowering the motor, you can do it with the motor right on the trailer if you are interested....
Steve |
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Posts: 388
| I am interested. Do not have a lift but remember some discussionaround using the motor hydraulics to adjust transom mounting point.
Would appreciate more info.
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Posts: 3504
Location: Elk River, Minnesota | Here you go...
1st: tighten down the transom straps to keep the boat on the trailer for this process
2nd: lower your tongue jack as low as it can go. Level out the motor so it is perpedicular to the ground, then place blocks under the skeg until they are touching the skeg.
3rd. Remove the upper transom bolts
4th. loosen the lower transom bolts a ways so the silicone will break free.
5th. crank the tounge jack up until the next set of bolts line up with the bolt holes on the motor. you may have to use some side pressure (push up on the side of the outboard on both sides (like rocking it back and forth) so the silicone breaks loose. Once loose, it will be able to let the boat move but the motor will stay in place.
Once the new bolt holes are lined, up, re-silicone the holes, insert the top mounting bolts and tighten. Tighten the lower mounting bolts and you are all done.
If you are looking to lower the motor (which you should not need to do if you are looking to get cupping added) just raise the tongue jack as high as it can go, and just do the reverse.
First time through is always a little bit more nerve racking, but once you have done it one time, any other times will seem easy.
Steve |
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Posts: 388
| Thanks! Lowered the motor down 1 peg and will give her a whirl tomorrow... |
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Posts: 388
| Motor adjustment made little difference in hole shot, top speed, steering torque, or tendency to suck air with the SS prop. Still very easy to turn left and difficult to turn right. Adjustment was relatively easy to do with the instructions that you provided so I had little to loose in trying this before spending $$ to tune the prop.
I did consult my manual and found out that I adjusted the trim tab the wrong way when attempting to eliminate the torque issue. You move it to the direction that the boat wants to turn to make corrections. I did the opposite thinking I needed to oppose the direction that I was fighting it. Not sure I understand why it works that way but will give the SS blade another whirl with this trim tab setting and see how it goes at the lower transom setting.
I did try the original aluminum prop at the lower transom setting and it trimmed up fine without torque. Very little difference compared to what I was used to in the middle hole. Speed was about 1 mph slower than SS. Hole shot and top rpm were about the same.
For whatever reason it did seem a little easier to suck air with the aluminum prop so I cleaned up the shaft and propeller splines, and torqued 1 flat tighter than I had done previously. Noticed a little bit of galling / pitting on the tapered portion of the splined shaft and the mating surface on the stopper (which I had not previously removed). Suspect I had a little bit of play here causing this.
Edited by Yake Bait 10/11/2010 9:36 PM
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Posts: 3504
Location: Elk River, Minnesota | Hiya,
If the steel prop is of the same design as the aluminum prop, they will basically perform in the same manner. If this is the case, your findings would be what I would expect.
It does tell me, though, that you could move the motor back up and would be no worse for wear.
As for the torque tab, I would assume you were considering the trailing edge of the tab? When looking at the rear of the tab from behind the boat, the rear of the tab moves om the direction of what you feel in sterring torque. So...if you feel torque when trying to turn right, you would move the rear of the tab to the right. What the torque tab is then doing is creating more water pressure on the right hand side of the tab than on the left, which makes the front of the motor want to face to the left, ultimately turning the boat to the right.
Steve |
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Posts: 388
| Ran tonight and torque is good. Moved motor back up an will give it yet another whirl. Should be OK.
Thanks for the help!
Pete
Edited by Yake Bait 10/12/2010 8:42 PM
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