Problem is? Engine/drive x/gear
 

Problem- 2001 Daytona 26 walkthru bowrider will not fly.

Boat has standoff box with bravo xy 1.36 drive. Top of drive is about 1 1/2- 2" below rub rail, stock 30" bravo 1 prop

Engine is 540BBC, merlin VR marine 310cc steel heads, 8.0 compression, CMI elbow top headers, Crane cam # 139741 @ 50 lift 234/242 duration, 112 lobe seperation, gross lift 610/632, MSD digital setup, Procharger stage4 with 5" pulley. Motor has NOT been dynoed!

This last weekend after getting jetting correct. Boat has no problem planing, crusing at 2100rpms then hitting throttles motor raps to 4K instantly. Boat starts building speed after it seems like eterinty rpms go to 4200 very, very slow. (Boost at this time is aprox. 5-6lbs) I then get fed up & back out.

I had 540 twin turbo motor in boat before, best speed with above drivetrain was 89.9@ 4700rpms

I feel I should be in 100's easy but???

I was told when I had the turbo motor in boat I should go with 1.5 gears instead of 1.36. I talked to person that could not get his 26 daytona to perform until he change gear then boat woke up.

What is problem? I have been told cam wrong, something in engine, prop, gear ratio, drive height, & wrong boat.

My guess is that the engine won't really make real HP till you get it up around 5400. Cheapest first try would be a borrowed 26p prop but you'll probably end up going to the 1.5 gears eventually. --- Jer

It should be a rocket. I run 100 with 1.36 30"B1 5100rpm and IC/SC 502EFI. I wonder if the timing is too timid and retarded? That will make it very lazy. The CR is a little on the low side but will allow for more boost. Try a smaller pully. You probably don't make much TQ below 4000rpm- big cam, low compression, centrifugal S/C. Wouldn't you be happier to spend $500 and have it dynoed.

i would check the msd rev limiter. my guess would be that it's kicking too early but it works so smoothly, it may be hard to tell.
also, i would think that the 1.36 would be fine if you don't have a low end problem now.

Jpclear-
I am going to try & get a 26 or 28 for weekend to try

cobra marty-
I was going to get dynoed but I could only find one person in this town I felt would do it right & he told me to bring in & he would get to it after his vacationl. I wanted to get past all of the other problems so I installed in boat. If I exhaust everything else I will pull motor & have dynoed. Remember that NO problem coming on plan & motor screams to 4k from just crusing at 2100 rpms then falls on face. From 2-4K it is like prop is cavitating but boat is pulling strond, not a slow increase.

excaleagle42
You may have hit on problem. I am doing to download the owners manuel for this box. If I remember right this box has 2 different rev controls, 1 max & 1 for something else. I have an old analog MSD box & going to take that along to lake this week end & try.

I have been gaping plugs at 35 but in talking to engine builders today I am told I should go to 45 but they do not think that is problem

It could be two-fold, the engine is now making enough HP to break the prop loose when you acclerate from 2100rpm, then the MSD rev-limiter is kicking in early. I'm not familer with the digital box, but on the blue #6 box you can simply unplug the rev-limiter. Getting the drive height right can be a frustrating job. Good luck.
Robert

Last night I checked msd digital6 box & had rev limit set at 5800 for both settings. I read that if you set to "0" it take rev control out. I also found my old msd6 box so will try this weekend also.

I hope you can get this worked out. I've had your engine as wallpaper on my monitor for the last month. What is your fuel pressure when this is happening? Does it coincide with the opening of the secondaries? My guess is carbs. May be easier to figure out on the dyno where you have fuel flow numbers to look at. Good luck.

another thought, the engine is getting to the rpm's where serious torque is made. is the prop a solid hub or could it start slipping? i assume your running a single dominator carb?

TJ-What did you end up with on your jetting, I was reading your post on eliminator section and it looked like you were still working on jetting. Sec Agent Man nailed your jetting on the head, this motor won't make power if its too fat? How did your plugs look at WOT, they should be tan and not sooty at all, if it is clean. I haven't attained that point with my Procharger but I am working on it. Since we last talked, I turned my box base around, lined up the the carburtetor with the plenum, and flared my intake roofs up to the flange. We'll see how this works soon. I was reading in a Supercharging book that a centrifugal supercharger makes 1/4 as much boost at 3000 RPM's as it does at 6000 RPM's. I believe you can partially fix the problem by giving the package a leverage advantage with a smaller prop, however I don't believe that is your problem totally. A lot of guys are running less motor(smaller than 540's) with only 5 or 6 lbs. of maximum boost, would be able to pull that prop and drive ratio past 4000. Your motor if tuned with 5 lbs of boost should make well over 6oo hp and 600 ft/lbs of torque, the key is if tuned. I can pull mine to 4000 with 1.5 and 32 with half throttle or less. There is 10% in drive ratios so yours would be equivalent to a 1.5 with a 33. You should rpm that quite easily. Go back to your tuning, I kept leaning mine out, checking my plugs till it made power. For god's sake don't leave out reading the plugs. I'll tell you my motor wouldn't get out of its own way when it was too rich. Keep us posted. By the way the weather has not been cooperative for trying out the Nickerson carbs on Dave's boat, but the boat is ready to go and I'll update you when it's accomplished.

jspeeddemon - What setup are you running? Carb, intercooler and compressor? Any pictures?

I am running a 540 BBC, Canfield 350cc Aluminum heads, Stage 4 Procharger with dual carbs and intercooler. The boat is a 26' Daytona with XR drive and 1.50 gear ratio, turning 32 Bravo 1.
Initially had trouble with tyhe setup, I was real green on blow thru blowers, hell I'm still green but I learn everyday. I feel these Prochargers are designed for the masses, a generic to fit all applications, which is cool. However I am working on customizing mine to my boat. As mentioned earlier, the box
Tomcat-Loved your thread reply about the intercooler efficiency. The box has an offset in it, the carbs don't sit directly over each of the plenums, they are offset by 2" forward, so the air has to go thru the carbs and either bounce off of a shelf or make a turn left, to get down to the intake ports. I put a crank trigger ignition on mine, turned the base box around and lined the carbs up with the plenums. With your understanding of air give me some insight into the increased efficiency aquired by doing this. Also I ported the intake runners, blending the ports up to the flanges. I think there is a misconception among performance guys that the air gets blown in the cylinders no matter what the restrictions. However if it is true that a supercharger increases the density of air versus more quantity of air, then increasing the ability of the motor to breathe should result in more power and more efficient burning of fuel.
May I pose a question to you Tomcat? If a naturally apsirated motor takes in a coffee cup of air per valve opening as a rule of thumb, and a supercharged motor takes in that same coffee cup of air, just packed more tightly, then my theory would be correct. The inefficiencies in the intake head combination would stand as impediments to making power. Tell me if you think I'm on the right track. I doubt I'll ever get this system to burn clean with carbs and will eventually fuel inject this motor, for now just making it the best it can be.

Your instincts are right. Supercharged engines respond to all the same airflow improvements as NA engines. Air is air. It has mass and it takes force to accelerate that mass. This applies when the air mass is accelerated from zero to some velocity at the inlet, but it also applies every time the air is required to change speed and direction. When changes in speed and direction are sudden, further resistance to air flow is caused by turbulence. Because the force driving the air through the "pipe" is the pressure difference between the two ends of the "pipe", these sources of resistance to air flow are often called pressure losses.

I didn't realize the dual carb box was like that. Your solution was smart and will reduce resistance to air flow. Sounds like it may improve fuel distribution too.

I agree that these kits are built to a price point and require massaging by the customer. That's exactly what I'm trying to do with the improved intercooler configuration. If we had a large budget, we would design a new EFI intake manifold, purpose built for intercooled supercharging, but instead we struggle with existing hardware.

I like your coffee cup analogy. It's true. The engine is a positive displacement pump, it always handles the same actual volume (ACFM). When you add the compressor and force more than this ACFM into the system, pressure and temperature go up because the actual volume is fixed. When this air passes through the intercooler, pressure and temperature go down because the actual volume is fixed.

Don't confuse this drop in pressure due to cooling with "pressure drop" a term often used to describe the resistance to air flow of an elbow or contraction or for that matter, an intercooler core. The resistance to air flow is a separate characteristic, and is more properly called pressure loss.

Jetting is perfect (at least I think) Last sunday I made about 15 runs at different rpm's (started at 2100 & at about 200+ each time) & checked plugs. Color was perfect evertime. Of course max rpm was only 4200. Jetting I have now is 68 primarys, 6.5 power valves & 83 secondarys. When I went from 8.5-6.5 it fixed the rich condition in the 2100-2500 range. NO BLACK on transom at end ofl day.

I PMed elimi & he is taking it easy on his motor but he has 26" prop 1.26 gears Had it running 90 @ 5000. He has a standoff box also.

I picked up a 26 & 28 prop to try for weekend.

I read on the procharger web site somewhere the other night & they were saying that a carb procharger system will put out more HP because the carb setup cools the air charge by 20-25 degrees more that if EFI is used.

Are your fuel pumps boost referenced? At 4000rpm and 5lbs boost your fuel might be dead heading. Take the S/C belt off and open the box and see if it pulls the rpms- sure at a slower speed.

tomcat

hi,
i think my understanding of this system is correct. basically, the procharger system is a centrifugal pump used to increase the net positive suction head or NPSH of the reciprocating pump , the engine for more displacement. the more laminar the flow, the less frictional losses and heat there will be because of decreased viscosity of the charge. thats where jsspeeddemon did help his engine work more efficiently by turning the box around. where you confused me was, when the pressure was increased and routed through the intercooler, the temp decrease and pressure decrease is due to the molecules slowing down and the suction of the reciprocating pump? and an engine likes laminar flow, a heat exchanger or intercooler, likes turbulent flow. turbulent flow would be like increasing an intercoolers surface area to increase heat removal through conduction. i don't run forced induction, yet. but my question is, about running intercoolers. could they have baffles to redirect the charge and increase the efficiency of the intercooler without causing a restriction? and if using centrifugal, could some guys in the quest for more power be actually hurting themselves by going to a smaller pulley and increasing the heat of the charge because of pump slip?
:rolleyes: thanks,
Fran

Fuel pump is the big aeromotive one for EFI engines. Yes it is boost refrenced. & have pressure gauge on top of box & on fuel line. As pressure goes up in box, pressure goes up on fuel.

Last night I was thinking maybe the coil??? Problem is motor does not miss out, it is crisp & clear. I am leaning towards the MSD digital box.

TJ-I think if your jetting is truly correct then surely you have ignition trouble. I think you won't find your solution in the smaller prop. Dave has a 28' V-bottom and he is able to pull a 32 pitch Bravo 1 to 5200 rpm with a 1.5 gear last year. That was with a set of Stainless Marine manifolds, I am talking the little ones designed for a naturally aspirated 502 or smaller, this year he will have the Lightning headers. We are expecting this same combination to go 5500-5600. You should be past that due to hull efficiency at if nothing else. Your idea to try the different MSD box is a good one. You be back to the 30 pitch when you get it right.

excaleagle42 - You're right about intercoolers liking turbulent flow but that only applies to the flow through the fins of the core, which are designed to create turbulence and improve heat transfer by "scrubbing" the air against the fins more. Before and after the core you want slower, laminar flow to reduce losses and help balance air flow across the face of the core. The precaution you have to take is not to use too much core face area and slow down the air velocity so much that the fins do not have turbulent flow. With core size restricted by the size of the average engine compartment this isn't usually a problem.

In industry we design cooling coils for a face velocity of about 500 fpm. A 540 engine with 90% volumetric efficiency will bring in about 850 actual CFM @ 6000 RPM. The Procharger 504 intercooler core has a face area of 12" x 7" (0.583 ft3). So the face velocity is almost 1500 fpm. I believe that should be plenty for turbulence within the core. This is the reason why Spearco puts cores in series rather than in parallel when they want to increase capacity. It keeps the velocity up, but at the cost of resistance to air flow. It's also easier to distribute the air flow across the face of a smaller core, which can be a problem with the typical ducted intercooler configuration.

The temperature decrease after the intercooler is obvious, the pressure decrease is due to the combination of resistance to air flow and the drop in temperature. For more on this, check out my post on what's really going on in an intercooled supercharged engine.

TJ-I think if your jetting is truly correct then surely you have ignition trouble. I think you won't find your solution in the smaller prop. Dave has a 28' V-bottom and he is able to pull a 32 pitch Bravo 1 to 5200 rpm with a 1.5 gear last year. That was with a set of Stainless Marine manifolds, I am talking the little ones designed for a naturally aspirated 502 or smaller, this year he will have the Lightning headers. We are expecting this same combination to go 5500-5600. You should be past that due to hull efficiency at if nothing else. Your idea to try the different MSD box is a good one. You'll be back to the 30 pitch when you get it right.

Tomcat thanks for replying to my question, it reaffirms my thoughts, I will let you know about the results, and once I get a baseline I'll would like to talk to you about your intercooler.

Turbojack - Are you getting into the secondaries at 4200? Have you marked the position of the throttle stick where the secondaries begin to open? What are your pressure readings in the box and the manifold at different RPM?

I'm assuming that you have no power valve on the secondary side so need to be 6 jet sizes up from primary to begin with. That would be 74s. Because the carb doesn't understand boost you have to go richer than that to get enough fuel when at full boost. You have 83s. That's a lot richer. Unfortunately that means as the secondaries begin to open at medium boost, they are way too rich. If you jet it down and start to see more RPM above 4200, you will prove this theory, but watch out at full boost!

Good luck!

Tomcat
"So the face velocity is almost 1500 fpm"

Can you put this is laymans terms?? A bigger number is better? From what I am reading I think that if the procharger

Last weekend I did not see if I could still get the 4200 at part throttle. I had marked the throttle as to where the secondarys start to open. I will check & see what rpm this is equal to this weekend.

Power valve only in primarys, these carbs do not have the option for them in the secondarys. Thinking while typing, power valves in the secondars might be good. I will try to get numbers this weekend at different rpm, boost pressure in box, & pressure in manifold. This way we could see where they would open based on the difference & what power valve would be used. I would say the power valve is good for max 6 steps. I have read the last couple of weeks, anywhere from 4-10 sizes. I have not checked the size of the hole in the carb block but it is small compared to the one in the 850 cfm carb I have. I also am needing to see exactly where(rpm) the power valve opens up. With 6.5 I would need a difference less than 3.25 psi. Procharge in last call last week said I needed 80's in secondarys & 4.5 power valve. Jspeedemon I think told me last year that he had a 2PSI difference between box & manifold. With a 4.5 PV almost would not open in that case.

In trying all these different jets I learned that a 2 step difference, 72 to 74 in primarys I could not get enought power to plane out boat.

Only check of difference I made last weekend was at 2200 rpms had 3 psi box, 5" vacuum in manifold & at 1000 rms in gear 10" vacuum & 1+ psi in box.

Sorry Turbojack, I wasn't clear. Air velocity of 1500 feet per minute (~17 mph) through the fins of the core will surely be turbulent within the core, a good thing for heat transfer. I don't know what the best air velocity is for these cores, enough to get a good scrubbing of air against the fins, but too much and the resistance to flow becomes a problem. If you look at Spearco's data you can see that as you put more air through a given size of core, you do remove more units of heat, but the percentage of heat removed, vs. total heat in the air, goes down. Since we have to work with what the manufacturers sell us this is pretty much besides the point.

When I said 74 jets I meant in the secondary side. Those jets would flow as much as the 68 jets plus power valve holes on the primary side for "square jetting". You need more than that to add enough fuel for the higher density air under boost, but 83 jets may be too big, hence Procharger telling you 80 jets. I'm thinking that when you note the position of the throttle you will find the overly rich secondaries are causing you to bog down at 4200 RPM. Nothing wrong with starting on the safe side. Do you have a pyrometer?

As for the power valves, you said that switching from an 8.5 to a 6.5 solved the rich condition between 2100-2500. You delayed the opening of the power valve holes. In your last post you said that you saw 3 psi (~6" Hg) in the box and 5" Hg vacuum for a total of 11 " Hg at 2200 RPM. You would think that would be enough differential pressure across an 8.5" power valve to hold it shut, but switching to the 6.5" power valve solved the rich condition so I'm not going to argue.

Procharger's recommendation to go with a 4.5" valve will delay the power valve opening even more, I'm assuming that means until the throttles are opened a bit more. This would also reduce the richness the engine is dealing with just before the secondaries begin to open. Sounds like a fine balancing act is required to get through this transition period and still have enough jet in the secondaries to support full boost density. Remember when we beat that topic to death?

It sounds like you're headed in the right direction. Good luck, and be careful!

Oh yeah, you have 1 psi at idle?! How fast are you spinning that compressor? What are you expecting as full boost?

crank pulley is 8.5" blower pulley is now 5" was 5.5" gear change is 4.41-1 so at 800 rpms impeller is turning 5998 rpms & at 5600 where is hope get to some day is 41,983

I stoped today & picked up new coil, dist. cap & rotor. Going to try this stuff first. If that does not do it I am going to see what prop change will do. It might work with smaller prop & will be able to get RPM's up to do plug reading at high RPM If rich I wll lean down more.

I thing I understand the air velocity thing now.

I am out of here to head to lake tonight.

And the problem was MSD digital box!! Replaced with old MSD 6 analog box & turned 104 @ 5600rpm's, 6 lbs of boost. Speed was still climbing but I chickened out. The MSD box I used did not have a rev control & was worried if I blew a drive, I did not want to take motor along with it. Just was glad to find problem. Next time to lake will be Memorial weekend & I will test to see what max is. & try different props.

TC I made list of Rpms, box & manifold pressures but do not know what I did with it.

RPM right where secondarys open was 3800, I think it was 0 psi in manifold & 6 in box at that RPM. When I find paper I will list.

That's great news! With 6 psi (12" Hg) across power valve it is shut right? So if you cruise just below this throttle setting your plug readings tested OK with the 68 jets. How does the engine respond when you open the secondaries?

Plugs look just a little lean at this point. Knock sensor is not showing any knock. Probem I see is in trying to come on plane with not much boost & throttle in secondarys. Motor wants to stumble just a little bit. Power valve is open, secondarys open, & my guess motor has too much fuel. I did not do a high speed plug reading after I made my one high rpm pass.


When throttle is open past primarys after cruise it hesitates for split second then it starts climbing fast.

Forgot to add humidity was at about 80-90%, temp was about 85 when we were doing the tests.

Sounds great. Now for 2" more prop and more boost!

yes, that is good news. at 104 mph though, i wouldn't consider that chickening out.:D
Fran

I am sure glad that you have gotten the setup close as you have to this point. Sounds like that thing is going to deliver what you wanted for power and speed. What prop did you have on it to get that speed and rpm?

Just got boat runing close to right, still not knowing top speed & already want to put smaller pulley on blower, install shorter drive, & ???

I spent last night wondering about the low boost (6-8 lbs, not quite sure what it was) at the 5600rpm point. Remember this is a 7.9-8.0 compression motor so I could put more boost to it. I do not know what the boost will be at 5800 point, I don't thing I want to spin it any tighter that that.

Jspeed- top of drive is 2" from rub rail. 1.36 gears stock 30" prop. What do you think about a 2" shortie drive??

I called MSD this morning about my box & tech I talked to said that the trigger wire need to be at least 4 -6" away from ANY other wire that has 12v on it. (gauge, power or any other kind of wire) He said if not it will cause problems over 3000 rpms. I asked about the other MSD box I used that worked ok & he said some boxes are more sensitive that others. TECH said I could ship him the box but all they could do was test & see if good, if bad would just throw in trash. Tech did not think it was bad. I wonder if this was problem with my turbo motor??