Need Help Badd!!!!! Going Crazy

[gforceauto]

have a sbc with the best of everything , that wont go above 3200 rpms...
i have been chasing this deamon for months and when i thought i had it licked i was wrong, it is a 383 sbc that has eagle crank, eagle h beam rods , aluminun pro action heads, ect ect. an 13 1/2 to 1 compression. it will hit 8000 rpms in a second out of the water but in the water 3200. i had the pump rebuilt also with a b cut impeller on a berkley pump. i will go threw what ive tried chasing this down.
1. changed to a new set of heads 1500.00
2. bought a 1200.00 msd marine distributer and box
3 went back threw the heads and installed different springs.
and still 3200 rpms, so i ordered a cam from lunati that they recommended and it was almost identicle to the one that was in it. the boat went faster with a 300.00 bone stock 305 than it is now.. so does anyone!!!!!!!!!!! have a suggestion,
please!!!!!!!!!!!!

[W.O.T]

dont spend any more $ until you get some good advice. what size boat? what kind of intake grate does it have? is it getting enough gas? is it bogging down on you or just stops revving? maybe that b impellor is to much for it.

[junkyardhunter]

what is the rpm range for your cam you need most of your power from 3000-5500 rpm

[78CoLe]

you runnin header or manifolds

[W.O.T]

the cam probably has no low end grunt

[gforceauto]

ok, i have headers, the cam goes from 2500- 5500, and not sure on the intake grate but it is same as it was when i had the 305 in it.

[78CoLe]

shoot got me then try advancing the cam 4 deg if able to

[junkyardhunter]

sound like you have problems.It only takes 90hp to spin a berk B cut @ 3200 rpm you should in the 5000 rpm range

[78CoLe]

if you can look up rampager or canuck their pretty good with small block in jets and good luck with the up hill battle

[gforceauto]

and it is a 16 foot tahati

[moneysucker]

I know I had a blower issue that kept me at 5200 for a couple years and I went through the same thing as you. CHeck your fuel filters and jets in the carbs, it could be clogged fuel system. You could have an air laek somewhere as well. What are your plugs reading? There is a ton of info that needs to be analyzed before you spend another dime. You are chasing ghosts wit $ bills and so far has gotten you a ton of spare parts.

[gforceauto]

new carb, filters, tanks. been over every gasget with a fine tooth comb.

[W.O.T]

is your carb and throttle linkage etc. working properly? if everything else sounds right maybe its a fuel problem. check your lines, filter, jets etc. never overlook the simple things. could be not getting enough or way to much fuel. what kind of carb setup do you have?

[gforceauto]

i had a race deamon on it, and bought a new holley to make sure. and every filter, gasline, tanks, nuts, ect are brand new

[Cas]

have you made sure the secondaries are opening up all the way?
Did you change the pick-ups in the tanks when you replaced them? If not, the little filter at the bottom may be clogged.
Have you also checked to make sure the tanks are vented properly? A simple test to check them would be to take the boat out, open the tank fills and go for a run.

[QuickJet]

Where is the cam in at?

[DUCKY]

This seems like it will be really simple, stupid little problem that everyone will over look. First, if you old motor was doing the same thing, how is the pump? Are you having a bearing problem that is binding up the impeller under load, or even worse, thrusting the crank against the block. I'd disconnect the H-bar and look there first. Also, you said someone rebuilt the pump. When and who? Was it before the new motor went in, and did they set it up right for your application. And are you sure that it is a B impeller?
And last but not least...You said you have already replace the valve springs, but have you checked the installed height, seat pressure, and open pressure.
Have you checked your ignition advance? What is it at idle and is it advancing with rpm?
And of course there is the fuel delivery as mentioned by others, what is your fuel pressure at the carb?

[gforceauto]

it has been built by one of the best motor builders around. but he's latemodel dirt track guy not boat, i realy thought it was the cam but when we yanked it and compared it to the lunati it was almost identicle to the 1000' nth. isky reccomended a small cam but the one i have is 2500- 5500. the motor sounds incredible and runs perfect but just has no a##. should i go more radicle with the impeller or cam? i dont know but 8000.00 into it and it just wont pull.
T

[gforceauto]

and the pump i had gone threw twice to make sure that wasnt the prob.
!. thought it was gas bought new carb
2. thought it was fire so i bought the best msd
3. thought it was heads so i bought the best i could find.
4. had the pump gone threw twice
ect ect

[Daytona100]

How about you dyno the motor. Should eliminate the guess work and probably save you some money. Throwing more parts at it and guessing gets real pricey$$$$$$$$ fast.

[Cas]

what are the cam specs?
All numbers would be great including lift, duration, int and exh valves opening and closing numbers. I'd like to do a guestimate on where the curves are on desk top dyno.

[gforceauto]

Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 3,000-6,500 RPM
Intake Duration at 050 inch Lift: 239
Exhaust Duration at 050 inch Lift: 249
Duration at 050 inch Lift: 239 int./249 exh.
Advertised Intake Duration: 278
Advertised Exhaust Duration: 288
Advertised Duration: 278 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.517 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.543 in.
Valve Lift with Factory Rocker Arm Ratio: 0.517 int./0.543 exh. lift
Lobe Separation (degrees): 106
Intake Valve Lash: 0.018 in.
Exhaust Valve Lash: 0.020 in.
Computer Controlled Compatible: No

[racincraft440]

Did you check your fuel pressure at that rpm with that load on the motor?

[centerhill condor]

like daytona 100 said..dyno time! this will help you better understand what is and is not happening...you may not have enough torque to get over the hump!

[Cas]

I couldn't find your exact cam specs for the intake and exhaust valve opening and closing numbers but I did find a Crane cam that is very close. The difference is .518 intake lift and .536 exhaust. The duration is 280 and 288 and the same operating range.
Since Desk Top Dyno probably isn't real accurate on the numbers.....I think it gives high numbers by about 7 or 8%. I think the tendencies are fairly close though.
At 3200 rpms there's about 180 hp (less 7% would be about 168) and the peak is up around 6500. The TQ peaks about 4500 which is pretty good. If the pump is absorbing 10%, it's down to 152, 20% it's down to 132 or so.
On top of all that, I don't know much of anything else on your engine so I entered info based on a better scenario. It's very possible that the cam isn't giving the engine enough oomph at that rpm to allow it to get into it's real hp range.
I'm with everyone else though, I'd be checking and double checking everything instead of tossing more money at it.
You mentioned it had a B impeller, what brand? There is a difference

[BOOGEYMAN]

What size are your fuel lines?? Are they just the cheap rubber ones or some nice braided fuel line? I wonder if you are pinching a fuel line down under a load??

[edog_103]

There is somethig definitely wrong. I am running a 1988 16' Carribian with a stock SBC. This summer I rebuilt the motor. Put a small Comp cam in it-RPM range 1500-5500, Edlebrock performer manifold, and a Holly 600 cfm vac. Secondary. It will turn 4,200 rpm, with an "A" impeller. Like previously stated sounds like the cam range may be too high.

[gforceauto]

have went threwverything twice. and my motor builders convinced its the cam or the impeller. Does anyone know a good marine engine builder that i can get cam suggestions i call all the major brands and get different numbers from all.
And i had it on the dyno once and me and the dyno guy got into it, and he's the only one around.

[Oldsquirt]

Gforce, before you go any further, go all the way back to the basics. There are some simple things that need to be double checked.
1.) With engine OFF, have a helper hold throttle pedal to the floor while you look down into carb to verify that the throttle blades are wide open. It is possible to connect the throttle cable to the wrong point on the linkage, preventing carb from opening fully.
2.) Ducky has already asked what your base and total timing numbers are. I will ask an equally important timing question. Have you verified that the TDC mark on balancer/timing pointer are indeed TDC for the motor? It is possible to use the wrong combination and have the timing very retarded. If you are using a balancer with an elastomer ring between the hub and outer ring, it is also possible for the outer ring to have slipped. Use a piston stop to find TDC and check it against your timing marks. Check this and then give us your timing specs.
3.)What is your fuel pressure at WOT at the max achievable RPM?

[gforceauto]

i have checked all of the above, except fuel pressure. now i have tried 3 different carbs. this motor sounds so good out of the water to be so slow in. It acts like it hits a brick wall all 3500. like it needs more gear if it was a car.

[1980Cougar]

you may not have enough torque to get over the hump!
I've seen 400+ horsepower engines in cars without a high-stall converter unable to spin the tires. If they can't get the rev's up to where the cam starts to breathe than they just bog.
If this cam can't make enough power at low revs to overcome the impellor, it might never make it into its power band.

[Floored]

where do you live?

[Duane HTP]

When you say you've had the pump gone through twice, was it by the same person both times? When you say it's a "B" impeller, have you measured it and know for sure that it is? If you're absolutely sure these are right, then do as Daytona 100 says and dyno the motor. One question that hasn't been asked here yet, and is very important; is your tachometer accurate? Be sure to check it against another tachometer to be sure.

[SmokinLowriderSS]

I'm trying to run this up on Desktop Dyno too, and not looking very good.
Without head data (I have a web-page FULL of head flow data, all brands,(http://users.erols.com/srweiss/tablehdc.htm#BBFord) but I am not finding anything I can connect to "aluminun pro action heads".
I went with DD's "Wedge/Pocket Porting, Large Valves" setting trying to get close to a hi-perf aftermarket head, used the factory large valve size(2.08/1.60), put a single plane manifold under an 850 4v, ran with "high-perf manifolds w/ muflers (which always got me very close on my BBC Taylor) and I got the following dyno numbers.
RPM / Torque / HP
2,000 55 / 21
2,500 115 / 55
3,000 185 / 105
3,500 229 / 153
4,000 265 / 202
4,500 296 / 254
5,000 314 / 299
5,500 322 / 338
6,000 315 / 360
6,500 298 / 369
7,000 261 / 348
7,500 231 / 330
8,000 189 / 288
Berk "B" HP requirements per RPM:
2,000 22HP
2,500 42HP
3,000 73HP
3,500 116HP
4,000 174HP
4,500 247HP
5,000 338HP
5,500 449HP
I'm thinking the cam selection has some "issues". Entirely likely the heads may be too free-flowing too. Seen big blocks on here set up for hi-rev racing that wouldn't spin a jet pump worth a damn. A certain 700+ HP 502 comes to
mind that couldn't pull the pump like my mild 454 would. I out-powered him untill 4,000 RPM.

[SmokinLowriderSS]

Just for giggles, I am making an "iterator" run on DD to find the best torque on this motor .... and see what it hands me. Gave it a pretty big range of cam specs to sift thru from 2,000 to 6,000 RPM.
365,904 configurations to run. Will report back.

[Cas]

Smokin,
Those numbers were pretty close to what I got the first time on DDT also. I then changed a few things around just to get some more power out of it thinking he has some real good stuff in it. You're right about the heads too!

[502 JET]

How big are the heads?Valve sizes?
If the heads are big volume ports and large valves (high rpm stuff) it may not be making enough power down low to get the pump spinning.

[SmokinLowriderSS]

Iterator run is 47%, I'll likely post best 1 in the AM .... before work. Getting late now.

[mrossum]

Berk "B" HP requirements per RPM:
2,000 22HP
2,500 42HP
3,000 73HP
3,500 116HP
4,000 174HP
4,500 247HP
5,000 338HP
5,500 449HP
not trying to hijack the thread, but do you happen to have these requirements for a panther pump. i'm runnin a mild sbc in front of my panther.

[gforceauto]

ok i think the main question was valve size 202 190. it is eagle crank , eagle h beam rods, speed pro pistons, aluminum protopline heads, lunati cam.
and the internals were all balanced. it push's 220 lbs in all 8 cylinders, with a race deamon carb and a 1200.00 marine msd to boot..... all brand new. and matching protopline intake, crower springs, fererra valves......

[SmokinLowriderSS]

not trying to hijack the thread, but do you happen to have these requirements for a panther pump. i'm runnin a mild sbc in front of my panther.
You just happen to be in luck. Panther with 450 impeller (I think the only one).
2,000 22
2,500 43
3,000 74
3,500 117
4,000 174
4,500 247
5,000 338
5,500 448
6,000 580
6,500 735

[502 JET]

Are you running racing gas?
Have you gps'ed the speed?
Is the tach correct?
Your timing light could be incorrect try another light and recheck the total timing.

[Havasu Hangin']

ok i think the main question was valve size 202 190.
What size intake runners? (I would think 200cc would be plenty for that setup).

[gforceauto]

200cc

[SmokinLowriderSS]

ok i think the main question was valve size 202 190. it is eagle crank , eagle h beam rods, speed pro pistons, aluminum protopline heads, lunati cam.
and the internals were all balanced. it push's 220 lbs in all 8 cylinders, with a race deamon carb and a 1200.00 marine msd to boot..... all brand new. and matching protopline intake, crower springs, fererra valves......
Well, I'll do a revision in the morning. I have found Pro Topline LIGHTNING head flow data ..... nothing on any plain Pro Topline head such as their stock replacement heads.
Have they been ported? The valves you spec are larger than anything Pro put in their heads. (1.95/1.60) that I am finding.
I'm still standing on a serious miss-match of parts to try to spin a jet-drive hard.

[gforceauto]

It Went Faster With A 300.00 Bone Stock 305. Than It Does With This 8000.00 Beast.. And Yes 103 Gas.

[gforceauto]

http://www.racingheadservice.com/Products/Heads/PA-SBC.asp
thats the heads ...

[SmokinLowriderSS]

Well, here is what I have now,
RPM / Tq / HP
2,000 95 36
2,500 147 70
3,000 209 120
3,500 252 168
4,000 288 220
4,500 320 274
5,000 338 322
5,500 347 363
6,000 338 386
6,500 320 396
7,000 281 374
7,500 252 360
My earlier guess setup:
2,000 55 / 21
2,500 115 / 55
3,000 185 / 105
3,500 229 / 153
4,000 265 / 202
4,500 296 / 254
5,000 314 / 299
5,500 322 / 338
6,000 315 / 360
6,500 298 / 369
7,000 261 / 348
7,500 231 / 330
8,000 189 / 288
Best torque setup Iterator came up with (my guess heads) looks like thisd
2,000 182 / 69
2,500 221 / 105
3,000 267 / 153
3,500 309 / 206
4,000 341 / 260
4,500 369 / 316
5,000 383 / 365
5,500 384 / 403
6,000 371 / 424
6,500 350 / 434
7,000 310 / 413
7,500 275 / 393
8,000 238 / 363
That was with the folowing cam specs:
Lobe center 105*
Int lift .520"
Exh lift .550"
60* overlap
Int Dur 267* @.050"
Exh dur 273* .050"
IVO-27
IVC-60
EVO-60
EVC-33
That should pull a Berk B to 5,000 before the pump's requitrements exceed the engine.
Running a new one with the "right" heads ... will report later.
I think it's a miss-matched engine.

[cfm]

Cam Style: Mechanical flat tappet
Basic Operating RPM Range: 3,000-6,500 RPM
Intake Duration at 050 inch Lift: 239
Exhaust Duration at 050 inch Lift: 249
Duration at 050 inch Lift: 239 int./249 exh.
Advertised Intake Duration: 278
Advertised Exhaust Duration: 288
Advertised Duration: 278 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.517 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.543 in.
Valve Lift with Factory Rocker Arm Ratio: 0.517 int./0.543 exh. lift
Lobe Separation (degrees): 106
Intake Valve Lash: 0.018 in.
Exhaust Valve Lash: 0.020 in.
Computer Controlled Compatible: No
You also have:
383cid's
200cc RHS/ Protopline heads (not chinese E-Bay Pro-Comps right ?)
13.5 : 1 compression - this is measured, not guessed right ? 220psi cranking compression supports compression in this area so I'm just checking
Above camshaft . For the compression it is actually small. Another way to look at it the compression is too high for that cam. This shouldn't be causing you rpm issue though unless you are detonating. I use cams like this on 10.5:1 - 11:1 flat top motors.
Which intake manifold ? Single plane or dual ? I thought protopline just made an intake for their 14 degree heads ? I could be wrong - okay, prob wrong. I'll go check now.
Have we tuned either of the carbs or just bolted them on ? Most out of the box carbs will have issues with a 106LSA cam . They'll need some tuning.
Have we checked fuel psi at carb ? Have we checked to see if fuel bowls are emptying (needle/seat issue) even if psi shows good ?
What exhaust system ?
What total timing / ignition advance curve / base timing are we using ?
Is coil / amplifier getting full voltage ?
==================
Sorry, can't help with jet pump stuff, no knowledge here.

[sleekvino]

maybe your timing on your cam is off it happened to me in my old boat it had a very small dot to line up i thought it would have been the big zero stamped on it but it had a very little zero on it and didnt see it un till oil got on it.the boat would never get passed 3500 rpms but it would idle fine just would fall on its face after that,i took the front of the motor apart and found it fixed it and it ran great,turned 4700 at 63 mph.

[GUGS102]

ok i think the main question was valve size 202 190. it is eagle crank , eagle h beam rods, speed pro pistons, aluminum protopline heads, lunati cam.
and the internals were all balanced. it push's 220 lbs in all 8 cylinders, with a race deamon carb and a 1200.00 marine msd to boot..... all brand new. and matching protopline intake, crower springs, fererra valves......
Does it have a retard on the box? How about the rev pill? Just thinking of simple things that can cause headaches.
Will it hold the 3500 or does it cut out?

[gforceauto]

it holds 3500 and sounds perfect, but it feels like it hits a brick wall and no more pull.and the msd is perfect, the fuel perfect. have checked evrything twice except cam size and impeller size.

[SmokinLowriderSS]

Well, here is what I have now,
RPM / Tq / HP
2,000 95 36
2,500 147 70
3,000 209 120
3,500 252 168
4,000 288 220
4,500 320 274
5,000 338 322
5,500 347 363
6,000 338 386
6,500 320 396
7,000 281 374
7,500 252 360
My earlier guess setup:
2,000 55 / 21
2,500 115 / 55
3,000 185 / 105
3,500 229 / 153
4,000 265 / 202
4,500 296 / 254
5,000 314 / 299
5,500 322 / 338
6,000 315 / 360
6,500 298 / 369
7,000 261 / 348
7,500 231 / 330
8,000 189 / 288
Best torque setup Iterator came up with (my guess heads) looks like thisd
2,000 182 / 69
2,500 221 / 105
3,000 267 / 153
3,500 309 / 206
4,000 341 / 260
4,500 369 / 316
5,000 383 / 365
5,500 384 / 403
6,000 371 / 424
6,500 350 / 434
7,000 310 / 413
7,500 275 / 393
8,000 238 / 363
That was with the folowing cam specs:
Lobe center 105*
Int lift .520"
Exh lift .550"
60* overlap
Int Dur 267* @.050"
Exh dur 273* .050"
IVO-27
IVC-60
EVO-60
EVC-33
That should pull a Berk B to 5,000 before the pump's requitrements exceed the engine.
Running a new one with the "right" heads ... will report later.
I think it's a miss-matched engine.
The latest creation by DD, this time using pro-topline heads airflow file I managed to dig up.
RPM....Tq... HP
2,000 216 82
2,500 252 120
3,000 294 168
3,500 337 224
4,000 367 280
4,500 392 336
5,000 404 385
5,500 401 420
6,000 388 444
6,500 361 447
7,000 320 426
Cam specs:
Lobe center 105.5*
Intake centerline 106*
Int lift .550"
Exh lift .570"
55* overlap
Int Dur 262* @.050"
Exh dur 270* .050"
IVO-25
IVC-57
EVO-60
EVC-30
THAT setup should spin a Berk "B" cut about 5,300 RPM before the pump cuts it off.

[mrossum]

it holds 3500 and sounds perfect, but it feels like it hits a brick wall and no more pull.and the msd is perfect, the fuel perfect. have checked evrything twice except cam size and impeller size.
try a summit 1107 cam in that beast. my gm pc dyno program shows some very promising numbers. specs on cam as follows:
.488 int / .510 ehx lift @.050
234 int / 244 exh dur @ .050
int c/l 109deg
lobe center 114deg
int valve open 8deg btdc
int valve close 46deg abdc
exh valve open 61deg bbdc
exh valve close 3deg atdc
gm dyno numbers
rpm hp torque
2000 129 338
2500 174 364
3000 218 381
3500 278 417
4000 341 447
4500 405 473
5000 459 482
5500 498 476
6000 521 456
6500 529 428
7000 512 384
7500 490 343
8000 442 290
i used small tube headers in this particular pull. big headers will net even more hp across the board

[mrossum]

You just happen to be in luck. Panther with 450 impeller (I think the only one).
2,000 22
2,500 43
3,000 74
3,500 117
4,000 174
4,500 247
5,000 338
5,500 448
6,000 580
6,500 735
god bless this forum.................................

[SmokinLowriderSS]

it holds 3500 and sounds perfect, but it feels like it hits a brick wall and no more pull.
That is exactly what happens on a jet boat when the pump finally overpowers the engine. The engine just leans on the drive and goes no faster. On my 400 HP 454, that happens on a berk "A" (my Agressor "B"), at 5,000 RPM, not a single RPM more, or less, from holeshot to flat-footed howling across the lake for several miles, no change till I lift my foot to slow down.
It was 4,800 last fall before I found 50 HP in a set of headers.
It was 4,600 that spring before the motor break-in loosened her up a bit by the end of summer.

[SmokinLowriderSS]

god bless this forum.................................
LOL. Glad I could help. :boxed:

[gforceauto]

God bless you all and all your help,
but i get more confused dailey.. let me get this right.. camshaft and impeller would prob be my best bet. if so what cut impeller do you all recccomend.\
thanks alot!!!!!!!! Tommy

[Cas]

None untill you sort the motor out
I agree but I'd also do what Duane suggested, take the pump apart and find out exactly what impeller you have. The brand of the impeller also makes a big difference.

[gforceauto]

a brand new berkley b cut

[Oldsquirt]

a brand new berkley b cut
If this is really true, then your engine is only putting out about 120hp at 3500rpm. It's hard to believe that even a terribly inappropriate combination of parts would produce such a weak output at that rpm. Something still doesn't add up. :confused:

[Cas]

Have you checked the length of the pushrods and are the rockers stock ratio?
kind of thinking out loud here trying to come up with some easier remedies.

[gforceauto]

I Took the heads to steelmans racing engines and had them gone threw, seat pressure, valve ange... all of the above. and it hits 8000rpms out of the water in the blink of an eye.

[cfm]

try a summit 1107 cam in that beast. my gm pc dyno program shows some very promising numbers. specs on cam as follows:
.488 int / .510 ehx lift @.050
234 int / 244 exh dur @ .050
int c/l 109deg
lobe center 114deg
int valve open 8deg btdc
int valve close 46deg abdc
exh valve open 61deg bbdc
exh valve close 3deg atdc
gm dyno numbers
rpm hp torque
2000 129 338
2500 174 364
3000 218 381
3500 278 417
4000 341 447
4500 405 473
5000 459 482
5500 498 476
6000 521 456
6500 529 428
7000 512 384
7500 490 343
8000 442 290
i used small tube headers in this particular pull. big headers will net even more hp across the board
My brain dyno says near (but more) the same #'s as this thing sits. Only part of his engine combo I don't know is the intake manifold - trying to find a pic of it - and the tune up.
A 383 with good heads (which he has) , 13.5:1 compression, and a cam around 240 at .050" is going to be in the mid 500hp / mid 500ft/lb torque range. If it's a dry header, then a 106 (as he has)-108LSA should make it pull pretty fast.
EX: a 383 with approx 10.8:1 compression, Brodix IK200 heads, Brodix 1016 dual plane , hydr roller with approx 240 at .050, belted out mid 500's for hp and mid 500ft/lbs. Again, this is pretty typical of a 383 SBC build with decent heads, cam, and 10.5:1 or more compression.
Copied from : http://www.brodix.com/IK%20Series.html
rpm..hp..torque
2500 130 273
2600 148 298
2700 163 317
2800 178 334
2900 191 346
3000 205 359
3100 221 374
3200 240 393
3300 266 423
3400 291 450
3500 321 481
3600 332 484
3700 341 484
3800 352 487
3900 366 493
4000 384 504
4100 402 515
4200 413 516
4300 424 518
4400 434 518
4500 453 528
4600 470 536
4700 485 542
4800 494 541
4900 505 541
5000 511 537
5100 517 535
5200 523 529
5300 529 521
5400 532 515
5500 535 507
5600 539 502
5700 544 501
5800 552 500
5900 561 500
6000 568 497
6500 562 461

[Oldsquirt]

Here's a pic of his motor from another thread. Looks like he's running a Demon vacuum secondary carb with electric choke on a fairly low profile manifold. BTW, looks nice.
Gforce, did you confirm that at 3500 rpm, out on the water, that those vacuum secondaries are actually opening? Were all the carbs you tried VS?
What size carb is it? What intake manifold? Have you run it without scoop and flame arrestor? Basically thinking about anything that could be restrictng airflow.
http://www2.***boat.com/forums/attachment.php?attachmentid=17399

[gforceauto]

I tried the 750 race deamon, and to make sure that wasnt the problem. i bought a 750 edelbrock new . so i am resonably sure its not a fuel problem.

[Duane HTP]

Put your enginie on the dyno. Find out how much power you are really making and at what RPM. If there is a motor problem, it will be easy to find and fix. If your motor is making good power in the rpm range that you need it, find out what size iimpeller you have. Then match the impeller to the dyno sheet. You're chasing ghosts here on the board getting nowhere.

[centerhill condor]

back to square 1...try to make nice with the dyno guy...its for a good cause..you can do it..maybe you could send some flowers and a card...or a subscription to hot rod..playboy..bigguns!?

[FILUCKY]

You need to know what your cam is installed at, i'll bet ya your cam is degreed in straight up or even retarded. If your motor was built for a dirt track car thats most likely what ya got and you need to advance it to 4* and see what ya get, hell ya can do it in the boat in a hour or two. I lost over 600 RPM from having my cam straight up, went 4* advanved and hit 6800 up from 6200 thats over 200HP gain so figure that on a 400Hp motor and that could be your problem. Where your cam is set determins where your power curve is, advancing your cam brings your power level down and retarding it moves it up in the RPM range, move it up just a little to high and now you can't break over the hump to reach your motors big HP numbers. Its just like holding your foot on the brake in a car with a auto trans with a stock converter if you don't have lowend HP you can't start spinning the tires to get up in your power range, your jetpump works pretty much the same way.

[don johnson]

I tried to read all the posts and did not see where anyone suggested you check the coil and MSD box.
I just had a similiar thing happen with one of my motors, 1,100 HP blower motor. The connections on the coil got corroded and the motor would run great up to 3,500 RPM then it just stopped making power. It did not crack or bang, simply stopped pulling.... I cleaned the contacts and I was back in business. I have heard that a bad coil or box can cause this same type of scenario....
One last thought, are you getting 12V+ to the MSD box? If not that could lead to the problem. MSD's get grumpy when under 12 volts