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1988 starflight hull performance?

Jackscm88225

Jackscm88225

Member
I am hoping that someone here has some info on these hulls. I have had this boat for 5 months now and have been playing with motor height and props.

I have a 1996 3.0 mercury 225hp. motor that runs great! I started with a 21p aluminum prop and the motor height with the cavitation plate even with the v. The motor ran at 6000 rpm and the rev limiter was holding it there. My speed was 62 on the Speedo. But the boat ran straight and smooth. Then I tried a 26p cleaver prop that ran at 5800 rpm. And a speed of 64 mph. and the boat wobbled back and forth. If I did my math correctly I had a lot of prop slip with this one. So I put a 25p Trophy plus on and my hole shot suffered and I could only get 4800 rpm. At 59 mph. boat ran smooth and strait. I tried raising the motor about 3 inches and with the trophy plus 25p prop I got 5000 rpm. And 63 mph. and it wobbled again just like the 26p cleaver. Is this the prop or the boat? It seems that when approaching 64 mph. this happens. I think I need a 22p prop to get the proper rpm. But then I will have speed I can’t use. Any tips on this?
 
Thanks for the info and the time to respond. I have my motor set back 6 inches and have a lot of bow lift. I am going to check my speedo to day with a GPS.My friend thinks I might have it over trimed at high speed causing it to wobble.
 
The wobble is called chine walk. More setback and motor height may help this, but you should also check your steering and make sure everything is tight. If you hold the steering wheel in one place you should NOT be able to move the motor back and forth.
 
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:bigthumb:Wobbling is chine walking, Also to help stop you need at least dual cable steering that is tight.Nice fresh,not worn mota mounts if not solid mounts.set back,engine height,right props,straight bottoms,ect.ect. all play a hand
Do all you can do with your set up then learn to drive thru the chine walking a 3.0 225 should have enough to push you thru it!

In the bow behind the bulkhead is apx 3ft of foam that can hold up to 100lbs of water need to check that out.If that is true that would add greatly to your over trim proplems

Good Luck,Merc245
 
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Thanks for all the input guy's. I have hydraulic steering that does not have any air in it at all so it is very tight. Motor can not be moved unless the steering wheel moves. I have always let off of the throttle when it starts to chine walk. My only thought was it would get worse and not go thought it and get better. It is not out of control but scary if you have never had this happen to you. This is the fastest boat I have owned and therefore don’t much in high speed behavior. Will try to hold it and see if it stops this afternoon. The weather is good today not much wind so should work out.
 
That motor should turn the Trophy up to 5500+. You may still be running too deep. You should have your propshaft between 2" and 3" below the V. You will find it improves holeshot and top end and reduce chine walk.
 
I have the prop shaft about 5 1/2" below maybe even 6" top of the prop is 1" above. So you are saying I should come up another 3" I do not have a low water pick up on my motor but I will try it and see what the water pressure is.
 
I think we may have misled you a bit... DO NOT try and throttle through chine walk. If you don't correct the side to side movement, it will continue to get worse until you get very wet. I would try what Mark has said to reduce/eliminate it. If that doesn't work, you will have to drive through it with steering input. There's a very good article around about chine walk... I'll see if I can get a link for you.
 
One more question? I have not completely remover the vent plugs to get the largest opening yet. What rpm. should I get when coming out of the hole. Also there is a plastic ring on the back of the prop to stop exhaust from coming around the prop. Should I remove that to get more rpm. to take off. I can see that raising the motor will put the prop in the slip stream of the boat and help also. I have the motor in the position that's in because the first prop I used let go when trying to get on plane. But that was a 21p quicksilver prop. Not made to run near the surface.
 
These boats do start to get light at about 63 mph. I know mine does. The boat will start to walk a bit. BUT, as long as you get some seat time and learn how to correct this before it gets out of shape, you should get close to 70 with that setup.

Matt
 
Thanks for that info. Very helpful! I think I have been trimming it up to high with the front way to far in the air. But I still am going to raise the motor about 3 1/2" and try my prop one more time. Not going to try and drive through the chine walk but slowly trim up at WOT and see how it responds to the new motor height.
 
One other thing to mention- you should shoot for the propshaft to be parallel with the water surface to be most efficient with your power.
 
Thanks for all the help! On my way out to see whats it is going to do before the rain on Wed. Would be nice if I can keep what I have instead of spending more $$$.
 
6" of setback is not a lot. standard from the factory but most people run a lot of setback on a starflite. the bow is heavy, real heavy and doesn't want to un-stick from the water without tons of trim = chinwalk and blowout if your engine is lifted too high for the prop you run. I have run a chopper on mine for a long time and everyone on here says the trophy is the best prop to run, better control in the "chine walk speed" of 64+ mph. The cleaver is the wrong prop and the 25p is a bit steep for 225 hp on this heavy of a boat. I run 22p 3-blade and turn it up to 7000 rpm jacked real high with 250 hp. Hydraulic steering is a must which you have and even with all these things there will still be chine walk because the starflite is not a pad v-hull.
 
Well I have to say that all of you have had some good input into this. And mark was right the height of the motor is everything. I measured from the V to the prop shaft and had 6 ¼ “below. I adjusted it to 3 1/2” which brings only the two bottom holes for the water pickup below the V. It still worked fine if trimmed right. I also removed the plugs from the prop ventilating system and left the back ring in place for this run. The chine walk starts at about 64 mph. but is not as violent it now moves back and forth a little slower and is not so intimidating. My hole shot is very good compared to before the rpm jumps right to 3400 and when the boats starts to lift it comes up to 3900 and then it grabs and off I go. The prop being higher in the slip stream really helped the take off. And it gave me 2 mph before the chine walking set in and topped out at 67.1 – 67.4 gps at 5400 I was able to trim it higher but all that did was shoot more water in the air which it did not do before and I lost speed. With a nice rooster tail ( fun! )I had 5800 rpm and 62 mph. I am having to put a little steering in with the new height at WOT. Might still need to drop a pitch or two. I would like 5700 with it trimmed out correctly and maybe get a mile and hour or two more. But the changes made it nicer to handle and my speed is up so thanks to everyone for their time
 
You may be as high as you should go with the setback you have. I think you have the right prop with the Trophy. If you stack another 5-6" of setback onto your plate you will be able to go up another 1" to 1 1/2" without losing water pressure. You will gain 300 RPM and 3 MPH. You will always have to add positive trim on a Starflite as they are just too bow heavy free up the hull without it. Keep playing with it. Getting there is half the fun.
 
Jack, it sounds like you're on the right track. I'm no top speed expert, but I've got the same motor and hull (with a bit more bow weight) as you. I have NO setback (yet) and am running 4" below the V. My best GPS speed was a tad over 64mph with a 26p trophy only turning around 5400 rpm. I seem to remember this being around 65 on the spedo. Last year I saw over 70 on my spedo (no gps) with a 24p trophy turning 6K rpm +/-. This year I didn't take the silly 19P big ear ski prop off so I have no new #'s (shame shame shame).

I've tried a host of 3,4,5 blades and own 2 tr trophy's. On my setup the 4 blade is the best handling prop. A TP 4 blade would also probably be very good

One other potential issue with that motor is that the primitive ECU / EFI system can get tripped up and advance the timing at WOT (actual cause of this is open for debate, but many people have felt the end result). I have been running at WOT and pulled back slowly to 3/4 throttle and the boat ACCELERATES, then you can ease into the throttle and rev out yet further That was when I saw 70 w/ the 24P. I think this has more of an effect when trying to turn a bigger prop - if you're already running 6K, it may not be an issue. Just something to try...

Good luck and keep us posted!
 
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