Thunderstruck

Cones worked well for me but you need some more WOT data as you said. Let us know how you do this weekend.

Madkat

Sure will. Im glad the cones help you out, sounds like they are working great for you. I my try them, but not until I get everything dialed in first.I would also like to try a set of 32's. From the info ( dyno sheet )that I have gathered so far is that from 5900-6000 rpm, the motors are making only 5 hp more. We built this motors to peak at 6000 rpm. with the 30's I can run them up to the 5900-5950 mark. I would rather run these motors at 5800 to give me a 200 rpm cushion in case I come out of the water, plus you are not going to see any mph gain by running them the 200 more rpm if you are only making 5 more hp. If I run the 32's, that should drop me down to the 5600 mark and then do some labbing to them to bring them back up to the 5800 mark. I am not sure what gain in mph I would get from going up to the 32 from the 30. I am estimating a possible 2 -3 mph gain. I will defenitly post some numbers after this wknd.

Thunderstruck

My problem was little difference in speed between 28 and 30 pitch props and lab vs. no lab made no difference which it should. I was running 86 mph at 5550 rpm with 30 bravo I's and other props which is 15% slip. Nose cones brought me to 5450 rpm at 91 mph with labbed 30's which is 8.8% slip. Big difference. (I went out by myself w/ 1/4 tank gas, light chop and got another 1 mph after I posted the original 90 speed.)

Tom

Madkat

Sounds like the nose cones really helped you out. When my motors were stock, I was running about 82-84 mph at 5200 with 28. After the rebuild, I gained about 200 hp per motor and gained 6-8 mph at 6000 rpm with the 30's with best speed of 92 mph (about 9.0% slip). I didnt have alot of hrs on the motors then. Now that I have about 45-50 hrs,I will really see what it can do.I know I should be able to spin the 32 with no problem and possible 34's. If I could hit 100 with the 32 and nose cones, I would be really happy.

Thunderstruck

Check your slip numbers. I got 16% slip for you assuming 1.5:1 gear ratio using 30"-1 = 29" for the prop in the calc per Throttleup's (Julie and Matt) recommendation. It's worse if you use 30" for the prop and 1.36 gears.

Check out:

http://www.go-fast.com/Prop_Slip_Calculator.htm

Tom

Tibbstoy2

iTrader: (1)

Hey Madkat, what port are you running out of? And if you're on the west side of Michigan, how good are your mufflers?

Also, what type of notch are we talking about here on these 32's? Mine's a 1997 with no noticeable notch on the back end of the boat. I just haven't seen many around in Michigan to know the difference.

Madkat

Tom,

I will trust you if you say there is 16% slip. I tried at least 10 times putting in the dats and I get nothing. Never been good at using that calculater. Once I see what she does, maybe you can punch in the numbers and see what my slip is

Madkat

I run out of Lake Erie and St Clair. The mech. that did my motors lives over in Marne Mi. We were getting yelled at when we took it for a test drive last year over your way. On our side of the state, they dont say a word to me. I have never been pulled over for excessive noise. ( Yet). What is your email address. I just noticed that our membership is up and I cant post any pics.

Thunderstruck

No problem, let me know whatever you need but, if the website doesn't work for you:

The formula is:
Slip = (1-actual speed/theoretical speed) x 100%

Theoretical Speed = rpm x pitch/1056/gear ratio

Or in your case:

Theo. Speed = 6000 X 29 /1056/1.5 = 109.9 mph

Slip = (1-92/109.9) X 100% = 16.3%

If you get your slip down to 10% with cones or whatever, your speed at 6K with 30's will be 109.9 X (1-.1) = 99 BABY!!!

Madkat

Thanks Tom.
Makes alot more sense now. i will let you know on monday.