Turbojack

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.

jpclear

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

cobra marty

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.

excaleagle42

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.

Turbojack

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

Tonto

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

Turbojack

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.

tomcat

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.

excaleagle42

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?

jspeeddemon

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.