Dave M

1.65 ratio? Why not 1 .5 with a smaller prop? I know someone with a non-step 27 w/500 HP and he is running 74-75. He's running a left handed Hydromotive.

Dave M

Do you know Bruce's last name? Where are you located?

GOODT

You should be in at least the mid to upper 60s if not get it checked !!!!!!!

BajaRunner

I know a guy who bought a 33 outlaw with 496's and they did the same thing, 1.65 ratio with 30p bravo 1.

I dont understand why.

Von Bongo

a 1991 isn't a step bottom boat...95 was the first year...

My 95 with a 325 hour 385 HP 454 MPI ran solid 66. Ran a left hand Mach I prop. Thats why I figure you either have the wrong prop or your motor isn't putting out much HP. Before you go swaping out stuff need to figure out where you are. I think my Mach was a 21 pitch LH 4 blade.

Not to sound stupid, and to cover all the bases, what are you trimming out too? If I remember my boat hit WFO at 6.5 on the drive indicator. I am sure it varies depending on set-up but it isn't unheard of people not trimming out at all.

a 19 pitch may have you bumping the limiter...you should try to borrow a 21 4 blade and see what you can pull for max RPM. Try a hydromotive or a bravo 1. If you can't spin a 21 then the HP your engine is putting out would be suspect. You can do a compression and leak down to make sure it's healthy. If OK then I would start to look deeper into what manifold, carb, jetting and so on you have.

Also be nice to find out what your compression ratio is, as has been said you may have a motor that was set up at 7-7.5 to 1 for a blower. If so I would take the easy rout and make it a 525sc except with a 502 instead 454. YOu could run 5 lbs of boost and live for ever if it is a low compression set up.

Von Bongo

That's dialed in, the step bottom boats barely run that with a 500 EFI

pullmytrigger

the Bravo 1s, Mirages, Hydros, Machs will all fit.......you can try left hand and right hand operation by putting the shifter in reverse if your prop is turning right and you want to try a left hand prop (it can make a difference from a right hand!).......props props props!!!......Im pretty sure max hp for that engine is 51 - 5200........you say it runs 58 and your looking for 65?.......I dont know if you'll pick up 7 from a prop change but 4 or 5 is not unheard of.........dont ever for one minute think all 3 blade props are the same and all 4 blade props are the same.........Merc , Hydro and Mach allmake 4 blade props but the fact they have 4 blades is about the only thing they have in common.....they're all different.......try some props!!!!!!!!!!!!!!

sleeper_dave

Right now, i'm not far from you (Aberdeen, MD, traveling for work). I live in Harrison Twp, Michigan, though.

Don't know Bruce's last name. Heads Up Racing is the name of the company, and apparently Bruce managed to win some races by hiding the nitrous in the roll cage at some point (per an anecdote i heard 3rd hand), that's all i know. Heard he's good at building big-blocks, from a source independant of the marina that sent my motor to him. I'm going to call the marina i had do the work (Beacon Marine in Harrison Twp.) and see if i can't get more details on the motor.

Believe me, i trimmed it out. When i was 12 years old, i figured out how to trim out my dad's Silverton 34X to get max speed (35.0 mph, for a few seconds at least). I'm not leaving the bow buried and then complaining about the speed, although i can see people doing that.

I'm not sure how well the trim indicators are adusted. I've run with the tabs up, and with the tabs almost horizontal and haven't noticed much of a difference. There seems to be quite a bit of slack in the right indicator though, if i move the tab in the opposite direction it takes a few seconds for the indicator to start moving again.

I had trouble discerning a speed difference between 4-5 on the drive trim indicator and 6 or so. I did notice more vibration at anything but about 4, though. It'll get a new u-joint this winter, even though it didn't seem to need it when the motor was pulled.

BTW... WFO? Wide f'n open?

Does this thing even have a rev limiter? Thunderbolt IV ignition. Crappy enough tach that i have to hit it to get a decent reading (also will be fixed over snowy season). If it's hitting the rev limiter, i haven't noticed. Although when it leaves the water i'm usually not looking at the tach (but i do pull the throttle back). Honestly, i could have sworn i heard valve float on the first big wave i hit at WOT (before i had the motor rebuilt). I would be surprised if it has a rev limiter.

On the list so far:
1. redo the dash
2. fix the upholstry that's tearing
3. drive shower
4. intake (cheapest performance mod i can see)
5. possibly carb (any insight on how i can tell what i have? 8867 and a W on the top)
6. prop
7. u-joint

not in any specific order

They say a boat is a hole in the water that one throws money into. That's just not true. Most of the time when i throw money at it, it's on the trailer.

Do pictures work on this site if they're not attachments?

let's try

tcelano

Here is what our software says you should get out of a late model at 5000 lb with 1.65 gears and a 30" B1. Looks a little tall still to me, and there might be more in it with a little higher drive height or a lab finished prop.

Manufacturer: Fountain

Model: 27 Fever

Length: 27 ft

Beam: 8 ft 4 in

Weight: 5000 lb

Deadrise Angle: 22.5 deg

Hull Depth: 5 ft

Number of Running Strakes: 2

Number of Transverse Ventilated Steps: 1

Hull has a keelpad

Boat has an open cockpit

Engine information:

Boat has 1 x 502 c.i. Normal engine installed

Engine Redline: 5300 RPM

Peak BHP is 415 BHP occuring at 5200 RPM

Peak Torque is 450 lb-ft occuring at 4400 RPM

Drive information:

Boat has 1 x Bravo One, X, XZ, XR Drives Installed, with 1.65:1 gears

Propeller information:

Propeller: 4 bladed Bravo 1

Prop Diameter: 15.25 in

Prop Pitch: 30 in

Prop is set 24 inches behind, and 6 inches below the running surface

Environmental Conditions:

Boat is to be simulated operating in Salt Water, at 0 ft above msl, with an ambient air temperature of 80 degrees F

Program Completed

Computational Results
Your boat's computed performance is as follows:

SPEED(mph) ENGINE RPM REQ'D BHP AVAILABLE BHP PROP SLIP WETTED LENGTH(ft)
25.00 2309 92 177 38.02 14.49
26.00 2363 96 182 37.01 14.03
27.00 2420 100 188 36.12 13.74
28.00 2478 104 193 35.28 13.48
29.00 2533 108 199 34.42 13.08
30.00 2591 112 204 33.67 12.85
31.00 2646 116 210 32.88 12.49
32.00 2705 120 216 32.21 12.29
33.00 2761 124 221 31.50 11.96
34.00 2820 129 227 30.90 11.78
35.00 2876 134 233 30.25 11.48
36.00 2932 138 239 29.63 11.20
37.00 2992 144 245 29.12 11.05
38.00 3049 148 250 28.55 10.79
39.00 3105 153 256 28.01 10.53
40.00 3166 159 262 27.56 10.42
41.00 3223 165 268 27.06 10.19
42.00 3280 170 273 26.59 9.964
43.00 3338 176 279 26.13 9.747
44.00 3395 181 285 25.69 9.540
45.00 3457 189 290 25.34 9.459
46.00 3515 195 296 24.93 9.265
47.00 3572 201 301 24.54 9.077
48.00 3630 207 307 24.17 8.897
49.00 3689 214 312 23.81 8.724
50.00 3747 221 317 23.46 8.556
51.00 3805 228 322 23.13 8.395
52.00 3868 236 328 22.88 8.346
53.00 3926 244 333 22.57 8.194
54.00 3985 251 338 22.27 8.047
55.00 4044 259 342 21.98 7.904
56.00 4103 267 347 21.70 7.766
57.00 4162 275 351 21.43 7.633
58.00 4221 283 356 21.18 7.503
59.00 4280 292 360 20.93 7.378
60.00 4340 300 364 20.69 7.257
61.00 4399 309 367 20.46 7.139
62.00 4459 318 371 20.23 7.024
63.00 4518 328 374 20.01 6.913
64.00 4582 339 378 19.86 6.897
65.00 4642 348 381 19.65 6.791
66.00 4702 358 383 19.46 6.688
67.00 4762 368 386 19.27 6.587
68.00 4822 379 388 19.08 6.490
69.00 4882 389 390 18.90 6.395
69.23 4896 392 392 18.73 6.302

This next example is an older model, with no step, at 5500 lb, 1.5:1 gears and a 24" prop: I'd say this estimate looks pretty reasonable. You can visit www.speedboatperformance.com, and run the code for yourself. We've made it free to all users!


Manufacturer: Fountain

Model: 27 Fever

Length: 27 ft

Beam: 8 ft 4 in

Weight: 5500 lb

Deadrise Angle: 22.5 deg

Hull Depth: 5 ft

Number of Running Strakes: 2

Number of Transverse Ventilated Steps: 0

Hull has a keelpad

Boat has an open cockpit

Engine information:

Boat has 1 x 502 c.i. Normal engine installed

Engine Redline: 5300 RPM

Peak BHP is 415 BHP occuring at 5200 RPM

Peak Torque is 450 lb-ft occuring at 4400 RPM

Drive information:

Boat has 1 x Bravo One, X, XZ, XR Drives Installed, with 1.5:1 gears

Propeller information:

Propeller: 4 bladed Bravo 1

Prop Diameter: 15.25 in

Prop Pitch: 24 in

Prop is set 24 inches behind, and 6 inches below the running surface

Environmental Conditions:

Boat is to be simulated operating in Salt Water, at 0 ft above msl, with an ambient air temperature of 80 degrees F

Program Completed

Computational Results
Your boat's computed performance is as follows:

SPEED(mph) ENGINE RPM REQ'D BHP AVAILABLE BHP PROP SLIP WETTED LENGTH(ft)
25.00 2430 92 189 33.07 15.20
26.00 2492 96 195 32.13 14.72
27.00 2558 100 201 31.31 14.42
28.00 2624 105 208 30.54 14.14
29.00 2686 109 214 29.74 13.72
30.00 2753 114 221 29.05 13.48
31.00 2816 118 227 28.33 13.10
32.00 2882 124 234 27.71 12.89
33.00 2946 128 240 27.05 12.55
34.00 3013 134 247 26.50 12.37
35.00 3077 139 253 25.91 12.05
36.00 3140 144 259 25.34 11.75
37.00 3208 151 266 24.87 11.60
38.00 3272 156 273 24.35 11.32
39.00 3336 162 279 23.85 11.06
40.00 3405 169 285 23.45 10.94
41.00 3469 175 292 22.99 10.69
42.00 3534 181 298 22.55 10.45
43.00 3598 187 304 22.13 10.23
44.00 3663 194 310 21.73 10.01
45.00 3732 202 316 21.41 9.929
46.00 3797 209 322 21.04 9.726
47.00 3862 216 327 20.69 9.530
48.00 3927 223 333 20.34 9.341
49.00 3993 230 338 20.01 9.159
50.00 4058 238 343 19.70 8.984
51.00 4124 245 348 19.39 8.814
52.00 4193 255 354 19.16 8.764
53.00 4259 263 358 18.88 8.604
54.00 4325 271 363 18.61 8.450
55.00 4391 279 367 18.34 8.301
56.00 4457 288 371 18.09 8.156
57.00 4523 297 375 17.85 8.017
58.00 4589 306 378 17.61 7.881
59.00 4655 315 381 17.38 7.750
60.00 4722 324 384 17.16 7.623
61.00 4788 333 387 16.95 7.499
62.00 4855 343 389 16.74 7.379
63.00 4921 353 391 16.54 7.263
64.00 4992 365 393 16.40 7.246
65.00 5059 375 394 16.22 7.135
66.00 5125 386 395 16.04 7.027
66.85 5183 395 395 15.86 6.922

sleeper_dave

How much difference would i expect between salt and fresh water? I run in Lake St. Clair almost exclusively. Salt water is a little less dense, so a little more mph, right? 1-2, or something more significant?

Anyway, those calculations highlight my problem. I should be getting 65ish, i'm getting 60ish.

Will definitely try a prop. And i want to see if i can find out whether i have blower pistons or not. Blower pistons is a good enough excuse to get a blower, right? I mean, i already have the boost gauge...