littlejake

I took the boat out this weekend for some speed testing...I am running a 496HO in a 280 with a 24P. I hit the rev limiter which I think is 5200 rpm all day long with very little trim. So I was a little disappointed with 64.9 on gps.

My friend has the laptop program from Diacom and we ran it on the motor and I found out that my throttle position sensor shows I am only getting 85% throttle at W.O.T. So I bought a new one from Stem to Stern and it should be here shortly. So if science is right and if this sensor is bad I should hit the limiter sooner...right?

So I called Kevin @ R&R props in Vegas and got a 26P for $432 with overnight delivery(not bad). Hopefully this will fix my problem and get me closer to 70MPH.

Any input?

slider1

Bill R used to have a 280, and has been real helpful and tried lots of props. He had a 502 , ( same as mine ). Best performance bang for the buck was a Vortech or K&N flame arrestor. The fastest prop was a 24P Hydromotive Q-IV, a little over 70MPH GPS. I'm going to try the Hydro 25P P-5 on mine when the weather breaks. Hydro says the 5 blade will improve holeshot and midrange without losing top end. If not , I'll stick with the 24P Hydro.

Bob 280 Silencer,

Do you still have yours?? Have you tried any other props?

migpilot

Note that the TPS is a rate scheduler and not an absolute final value sensor. The ECU monitors how fast the voltage is changing and is less concerned with the final value on either end (E.G. Idle and full throttle). You may want to check if you are getting full throttle blade travel. If you are you can measure sensor voltage and compare them to the values specified in the merc manual. I dont want to burst your bubble but if you can can verify full throttle blade opening then it is doubtful that you will see any change or increase after replacing your tps sensor.

Marc

powerquest 380

I thought about 65 was a good speed for a 496 28 footer? 70 sounds super fast for a 502, must have a great hull.

Its nice to hear someone else spending some bucks too.......
For a while I thought I was all alone on that one!!

Go littlejake

littlejake

I hear what you are saying but I dont understand the fix. I want to get 100% w.o.t. What do I have to do???? Did I waste time and money with a new TPS? I cant go wrong with the prop right?

migpilot

That 85% you are seeing (if the throttle blades are fully open) is a translation of a zero to five volt signal that the ecu is recieving from the tps. It should be close to 100% (5V)at full throttle. So replacing the TPS would be a good idea. What I was saying is if the tps voltage is less than it should be at full throttle, it doesnt mean you are getting only 85% throttle and you most likely wont notice any difference after replacing the tps. Fuel scheduling is a logarithym based on MAP, Temp, and throttle position, with the tps used mainly for rate scheduling. If you are on the rev limiter at low trim settings you most definetly will want to add some pitch or try a different style prop. If it is much cooler than you anticipate your normal boating temps to be you may want to wait until it warms up before getting to aggresive with pitch changes. I think you are on the right track and 65 is very respectable for your set up. Just recall though that it takes an act of god to get 5 more MPH.

BillR

My 280 w/ 502 and a labbed 26P would run 66 -68 all day. Here are some figures:

Stock:
Hydromotive 24: 4950 rpm @ 68 gps mph before blueprint**
B1-24 stock: 4750-4800 rpm @ 65 to 66 mph
B1-24Lab: 5080 rpm @ 67.7 gps mph (std lab)
4875-4925 rpm @ 66 (+ std added extra cup)
4990-5000 RPM @ 68 MPH. (+1/2 std added extra cup)
**No diffuser ring

After having my ECU recalibrated
Hydromotive 24P labbed: 5020 RPM @ 68.25 (Windy & inconclusive)
Hydromotive labbed: 5000 RPM @ 66.? (4 people 40-50 gal)
B1-24lab (-1/2 cup): 5150 rpm @ 66.5 mph (4 people 60 gal gas)
: 5170 RPM @ 66.7 mph (1 person, smooth)
B1-26lab (- ½ cup): 5000RPM @ 65mph 2 people 1/3 tank

After adding Stainless Marine exhuast
B1-26" 5100+rpm @ 66mph 3 people 1/3 tank
Hydro 24P 5100 rpm @ 69 mph 2 people 1/4 tank windy (w/ wind)

Best all around prop was a Merc Labbed Bravo 1 26P with 1/1000's cup removed.
Fastest prop was a Hydromotive 24P w/o Diffuser ring. One day I hit 71mph (gps) But that prop could be difficult to get on plane - esp if it was rough out.
This prop also liked lots of trim. The Bravo was trimmed to just a a needle's width above 1/4 on the gauge.
Want to hit 70 all day? Add a set of CMI headers. Best HP bang for the buck.

rainorshine

Its a pretty big stretch to get 5mph out of a prop change on stock power. Good luck, you might get lucky and hit on a good combo.

HiPerf2000

iTrader: (2)

Cold weather is good for some RPM's....so you may want to wait till the weather warms a bit to the normal temperature you will be running the boat in.

Slider1....

If the new prop works out for you, I'd be interested in your 24p hydro.

littlejake

Another great day at the lake...
ran the 26P stock with 60 beers, 5 bags of ice, 60 gallons of petro,and 4 people.

this is going to sound CRAZY!!!!! but with this much weight the boat handled BETTER?????

go figure!

No BS I used the same GPS and hit 67.4MPH!!

It doesn't make sense but like I always say..."It is what it is!!!!"


I dig it!