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Need help setting up a 87' starflite for top speed

rico649

Member
Good Days Guys, just purchased a 98" mercury 250 efi 25" shaft.(got a great deal)Motor will be arriving on friday so next week i want to start setting up my boat to go in the water. I just did the floor over and re-inforced the transom as well.
I'm looking to get maximum top speed out of my starflite. Can anyone help me with set up advice. like engine height, best setback, prop to run etc.
I will greatly appreciate it, thanks.
 
:welcome: The starflites are awesome hulls.
You'll get lots of good info here. I don't know much on the o'b setups but I do think the first thing you'll need is a 20" shaft.
 
I'm sure the experts will chime in soon but I can get you started in the right direction. Your hull definitely likes a 20" mid so I'd keep an eye out for one of those and then you'll need new lower unit or change out driveshafts.

If your positive you have a secure transom, add anywhere from 10"-18" of setback. My personal opinion is 10-12" is great but you might gain a touch more speed with a little more setback at a cost of increased proposing at medium speeds.

It's imperitive to have a water pressure guage and then jack that motor up; the higher the better as long as your getting good pressure. 3" below the pad is a pretty good starting point. If you have a low water pickup, you can get it higher and a nose cone can help you get a little more speed.

As for a prop... A 26P Trophy should be a good starting point.

What do you have for steering? You should be thinking of a capable hydraulic system as you'll be touching the high 70 mph mark and safety should be one of your first priorities.
 
Because I got a screamin' deal on a 25" shaft 175 Mariner motor, I run that on my Enchanter.

I would think that as long as you have the 25" shaft motor, you aren't going to want to go crazy with setback, as you'll really have to jack the motor up in the air, which will be detrimental to handling, as well as hard on the transom.

I have have a standard 6" jackplate, and run with the engine bolted as high as I can get it.
 
I'll start here with saying the same everyone else has. You are going to want to find a 20" midsection for that motor if you really want that thing to run at its best. And like Droptop5.0 said, if you haven't already, invest in a hydraulic steering system. I put a Sea Star Pro set up on my Starflite and loved it!!!! Felt so much safer running at higher speeds.

Here is how I had mine set up and got the best results. I ran 11.5" of setback, 6" extensions and 5.5" CMC hydraulic jackplate. It has been awhile, but I'm pretty sure I got my best results with the center of the propshaft 3/4" to 1" below the bottom of the V. I also ran a nosecone with a low water pick-up. I would not attempts to run that 25" mid motor that high, especially with no cone and LWP.

Once you get everything straightened out, she should be a really good running boat!!! I'm looking forward to seeing how this develops.
 
11-14" of setback, Sea Star Pro hyd. steering, 20" midsection, TorqueMaster gear case with low water pickups in the case (block off the upper 3 holes on each side of the gearcase by tapping them and inserting allen head bolts with thread lock), Trophy Plus 27 or lab finished Trophy Plus 28 or Mazco RE4-28. Start 2" below the pad...With a strong running 250 you should see speeds mid to upper 70's..
 

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Ok, appreciate the inputs guys. my goal will be to get a 20" mid section. for now, i'm going to run the 25 shaft and just jack the motor up via jackplate. what is the maximum setback you think i can run with the 25" for now? and how many inches below the V
 
Ok, appreciate the inputs guys. my goal will be to get a 20" mid section. for now, i'm going to run the 25 shaft and just jack the motor up via jackplate. what is the maximum setback you think i can run with the 25" for now? and how many inches below the V

The maximum setback has nothing to do with the 25" shaft. The maximum setback is limited by the handling characteristics of the hull, the strength of the transom and the center of gravity based upon the weight/length of the hull. In your particular case (a 21'2" v-hull that weighs roughly 1300lbs dry) 10"-12" is about the norm. I've heard of people running 14"-16" of setback on 21' hulls also but that would greatly effect lower speed porpoising and place more stress on the transom...I would mount your 25" motor at the highest hole settings on your motor clamp and raise the jackplate as high as it will go. Run a straight edge off the bottom of the "V" to the front of your gearcase. Then you'll get a good idea of how far below the boat bottom your propshaft will fall.
 
Ok, thanks. I'm planning on mounting engine today or tomorrow. I'll let you guys know how that goes. Using a 6" jackplate for now.
 
The maximum setback has nothing to do with the 25" shaft. The maximum setback is limited by the handling characteristics of the hull, the strength of the transom and the center of gravity based upon the weight/length of the hull.

In my opinion, having the 25" shaft directly affects two of the three things you mention. The boat with a motor with a 25" shaft is going to have a higher center of gravity due to the engine mass sitting higher, and it's going to put more stress on the transom due to the effect of the longer lever the motor is pushing on the transom with.
 
In my opinion, having the 25" shaft directly affects two of the three things you mention. The boat with a motor with a 25" shaft is going to have a higher center of gravity due to the engine mass sitting higher, and it's going to put more stress on the transom due to the effect of the longer lever the motor is pushing on the transom with.


Jumbofordman, It's relative to the size/length/weight of the vessel. Yes, I've also mentioned the higher center of gravity and the stress on the transom. In this particular case we're talking about a 21'2" hull that only weighs 1300lbs. If the boat was a 30' boat the equation would be quite different. The height of the motor would not effect the stress on the transom as much as the length of the setback. Remember, you can take a 25" motor and mount it at it's highest setting and it would yield you the same propshaft level as a 20" motor mounted at it's lowest setting.
 
Plus as mentioned earlier you'll want hydraulic steeering more than ever if you mount the engine really high. If using cable steering you will be putting a lot of stress on the cable ends due to the angle at which you will exiting the motor well on both sides.
 
Hey guys. Went out yesterday in the Starflite and i lost 10 mph. I'm still in the process of working on setup but last time i was out, did 65 and yesterday only did. 55
I removed the 6 inch manual jack plate n replaced. It with a 5.5 hydraulic. I also dropped the engine one bolt hole. Do you guys think that little difference made such a big change. I lost maybe an inch in engine high n 1/2 in setback. Now i have 11.5 instead of 12 setback. I also lost like 200-300 rpm. Am running a 26p trophy
 
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Hey guys. Went out yesterday in the Starflite and i lost 10 mph. I'm still in the process of working on setup but last time i was out, did 65 and yesterday only did. 55
I removed the 6 inch manual jack plate n replaced. It with a 5.5 hydraulic. I also dropped the engine one bolt hole. Do you guys think that little difference made such a big change. I lost maybe an inch in engine high n 1/2 in setback. Now i have 11.5 instead of 12 setback. I also lost like 200-300 rpm. Am running a 26p trophy


If you ran the engine 1 inch deeper and it was already pretty deep then yes that will hurt you. The less setback will slow it down more also but I agree with doing that with your 3 liter. You need to measure the prop shaft with the bottom of the V and see how much lower the center of the prop is. 1.5-2 inches below the V is where mine runs best. Also watch your water pressure!
 
Good Morning Guys. Did a couple of runs with the starflite over the week. The most i got was 64.7 mph GPS. Boat handles ok to me with 25" but I found a deal on a shortshaft(20"). Do you guys think with the 20" mid, I'll pick up any more speed? Because i dont want to buy it if its not needed. Boat transom is rock solid running 11" setback with no problem
 
Good Morning Guys. Did a couple of runs with the starflite over the week. The most i got was 64.7 mph GPS. Boat handles ok to me with 25" but I found a deal on a shortshaft(20"). Do you guys think with the 20" mid, I'll pick up any more speed? Because i dont want to buy it if its not needed. Boat transom is rock solid running 11" setback with no problem

It depends upon how high you can run the propshaft height in relation to the bottom of the keel. With 11" of setback you should be able to run your propshaft height anywhere from 1.5" below the bottom to 1.5" above the bottom. Retaining water pressure is critical when running the motor high!!! Make sure you have low water pickups and a good water pressure gage on board. You should see more speed with the 20" gearcase running higher than the 25"..
 
Ok. I did 64.7 with motor about 1.5 inches below the v. I have a fleet master foot with low water pickup. So your saying i can run my motor as high as 1.5 inch above the v? I have a water pressure Guage but will have to install it. What should my water pressure reading be for the safe zone?
 
I know this is a old post but like to know what was the end result as im looking to repower but finding a 20" is hard to find unless you want to spend big i can get many 25" but kind of sounds like you may have went back to a 20 please let me know your final results as a 20" 250 with the right set back and raised corectly with the right prop you should hit 70s all day long so wondering if you got that 25" in the sweetspot or not?
 
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