View Full Version : Upgrade the Predator to an MCX?????

10-16-2004, 10:04 AM
I know just enough about engines to get myself into trouble. :popcorn: It appears to me that the main difference between these engines is the intake manifold, EFI, and throttle body. Now I have a lot of components from the Corvette sitting in the garage and was wondering if this might be possible. I have a program, LS Edit that lets me get into the PCM for the Vette and was also wondering if this will work with the Mastercraft PCM????? Just looking for some input. :wavey:

10-16-2004, 12:00 PM
First, it's still under warranty. If you modify it, your warranty is history. Second, the 'Vette has a closed loop system, the boats don't. The ECM on the boats can be used on a car (like with the GM Performance Parts crate motors) but you would need to recalibrate (with correct fuel mapping and advance/retard) if there are any different air/fuel requirements after the mods are done. The TBI calibration is not the same as the MCX, but a dealer could be able to update it for you with the understanding that neither they, nor Mastercraft, are liable for any damage to you or the boat. Beyond the intake, EFI and throttle body, without seeing the actual specs on the rest of the motor, it's impossible to tell if it will be the same.

If I wanted to use spare 'Vette parts and not void my boat motor's warranty, I would be tempted to find a used 5.7L motor with the Vortec heads, roller lifters and rockers, find a shop with a dyno to test it so I would be sure it wasn't running too rich or lean and was developing the power I want in the right RPM range. Then I would probably do something goofy, like put it in a car or pickup that would never have had a motor like it in its wildest dreams.

10-16-2004, 12:10 PM
Hmmmmm sounds a little more complicated that working on the LS1. With the car, I can throw it on a Dyno, hook up A/F meter and start re-mapping the fuel curves. OK.......how about some different exhaust manifolds?

10-16-2004, 12:16 PM
Read my edited post, first. The exhaust couldn't have much less backpressure than on a boat. You won't get an improvement form that. Do you want more speed or do you just want to have more power for the sake of it?

The LS Edit only lets you do so much with the fuel, too. They know people will try the high and low extremes so they make it hard to go out of a range that's safe for the motor. Again, the car is closed loop and the boats aren't, so if you hook LS Edit to a boat, it's going to throw a bad O2 sensor code and may not let you proceed.

The dyno you put it on has the motor in the car, tested at the drive wheels, where in marine dyno testing, they mount the motor on the dyno and test it, usually without the trans. One of the main tests that us mere mortals don't usually have access to is testing for in-cylinder temperature, intake air flow volume and temperature, emissions and frictional resistance of the motor.

east tx skier
10-17-2004, 10:29 PM
Hey, Jim, just out of curiosity, any ideas for squeezing some extra horsepower out of the 351 HO? Not that I'm seriously considering it, but winter is approaching and I've got to have something to ponder.

10-17-2004, 10:38 PM
Go to a speed shop, preferably with their own machine shop. Otherwise, some NAPA stores can do the work and some have pretty good gearheads working there. Intake manifold, cam, porting and polishing all help it to breathe better and that's what gives you more power. A motor is basically an air pump, after all. More in=More out.

east tx skier
10-18-2004, 10:30 AM
Very good. Food for thought. So what kind of potential horsepower increase are we talking about?

10-18-2004, 11:48 AM
Mag, just my :twocents: but I wouldn't even consider doing anything to the engine as long as it's under warranty. My guess is that if something went wrong they would point to your mods and say it was somehow related to the problem. After the warranty expires you can go wild with it (if you want).

10-18-2004, 12:04 PM
Does the Magnuson-Moss act apply to boat manufacturers?
If it does, would it not allow a guy like mag to do what he wants or does it specifically apply to aftermarket parts rather than modifications such as the ones mag mentioned?

10-18-2004, 01:56 PM
I don't know of anyone who allows mods on anything and have the warranty stay intact. "Only authorized personnel may perform service on this equipment", or words to that effect. I don't remember the Magnussen-Moss Act anymore. What does that state, or should I look it up?

"Oh, the internet. They have that for computers now?"

east tx skier
10-18-2004, 02:17 PM
Jim, be careful or, eventually, every thread on this board will be full of Simpsons lines (not that that's a bad thing) ;)

10-18-2004, 06:00 PM
The Magnuson-Moss act that your reffering to regarding warrenties protects consumers who chose to use parts other than the manufacturers THAT STILL MEET OR EXCEED THE MANUFACTURERS SPECS. That means, if I want to use a WIX brand oil filter, rather than an Indmar brand oil filter, I can do that and not void the warrenty, becasue a WIX oil filter easily exceeds the manufacturers specifications for an oil filter. And yes this act applies to boats, snowmobiles, etc. This is to prevent manufacturers from stiffing you into buying their own product lines; oil, filters, plugs and wires etc. It's total B.S. when a dealer tells you that you need to use their product or else you might void the warrenty. Pure B.S.

NOW, if you go replacing your top end, and fuel mappng, you can pretty much kiss you warrenty good bye. You would have no leg to stand on if you expirienced any issues with driveability, starting, idle, etc, even so far as a burned piston, as the manufacturer would quickly point out that your "mods" possibly made it run lean, causing the problem. The only place you'd have an argument might be the bottom end, (IMO you WOULD have an argument) but the manufacturer would probably still claim, "Increased power...beyond the components engineered limits...blah, blah, B.S.) So I agree with JimN in this case modding would be kissing your warrenty goodbye.

Also, you LSedit won't work on the Indmar/GM designed computer. Not compatable. JimN is correc about no O2 sensor (your Vette has 4 of them) and no vheicle speed sensor either. Lastly, the TBI computer won't (practically) drive 8 MPFI injectors. You COULD make it work, but for way less money and effort, you could....

If you want more power out of your TBI Predator, get a bigger roller cam, and perhaps an Edelbrock Performer RPM intake and increase your fuel pressure/change your injectors to match it...after you warrenty is up -if you care. You've already got great heads (not LS-x great, but pretty great). Your cam is the limiting factor right now.

East tx skier, read my post under the thread "351 hp" or something like that, about increasing power in your older 351.

10-18-2004, 06:15 PM
OK, I do remember that Act, but the only parts that can be replaced by the consumer are filters belts and lubes, which are called "user serviceable". Anything that requires replacing moving internal parts is excluded, if I remember correctly.

Actually, the TBI computer is the same part as the MFI. The harnesses are different, though, since they don't just clip an extension onto the TBI injector plugs.

I'm not sure the Performer will make that much difference. If it was a stock car intake it would but as I understand, after the testing was done with a variety of intakes, this was used because it worked as well as a lot of aftermarket ones.

If more fuel is required, it's just a matter of increasing the pulse width. These injectors will pour in a pretty good amount of gas. If the MAP sensor sees low vacuum, it'll add more, anyway. A lumpier cam would help but I think porting and polishing would be a good start.

10-18-2004, 06:27 PM
That's why I said Performer RPM intake. I agree that switching to a Perfomer would gain you nothing. And I still think the RPM would only be a marginal improvement.

How would one go about increasing the PW of the injectors? If there is an easy way by all means, that would be the preffered route. If not that is why I said injectors and FP (FP first). I farted around w/a TBI car I used to have. I got it to 320 hp (from the original 170) using the original ECM and STOCK CHIP (!). I did this using large injectors, more fuel pressure, and a vacuum refferenced fuel pressure regulator. My car put down ~320 horse at the crank, and turn 24 mpg on the highway, so I think I got it pretty good for no chip tunning. If ECM tweaking is an option, by all means, that is the way to go, but there are options.

I can't believe they use the same ECM's! That's kind of lame. That indicates to me that the MCX or what ever they call it, is a batch-fire system. I assuemed all the MPFI's were sequential in this day and age.

Porting Vortec head is a lot of work (as much as an iron head) and it yeilds little gains, They are good already. There are some gains to be had on the exhaust side, bit the intake leave very little on the table. He needs more cam.

P.S. Adding a bigger cam (one w/more duration) is going to INCREASE vacuum at the higher RPM. It will only decrease vacuum at lower RPM and yes, at that point it will feed more fuel.

10-18-2004, 06:37 PM
Sorry, I missed the RPM part. By more vacuum, you mean with the throttle open, right? I meant what the MAP sensor sees below the throttle plate, not above.

I think the ECM can be programmed for either batch or sequential. Just a matter of using more pins and telling it how/when/how long to fire them. Although, since these are boats and don't need to be up-to-the-minute for the EPA, they may still be batch fire. After changing the cam and maybe the intake manifold, it may need a recal anyway and this would be the time to tweak the pulse width.

Alan probably has tons of recals that are from various versions of motors from development phase dyno tests. When I was down there for training in 2000, we did a recal and added an IAT sensor to a Predator owned by one of the techs where I worked, and they already had the recal program before we went there.

What did you do with the exhaust on that to get 320 HP?

10-18-2004, 07:01 PM
"... did a recal and added an IAT sensor to a Predator...."

That's a cool "mod". I have day dreamed about adding some form of "Cold air intake" to my boat. Like from the vent under the wind shield, run sealed 4" ducting to a sealed bonnet over the carb. Voila! Intake air ~40* cooler (than the current "under hood" air). So having an IAT would be cool to get the readings from. Even cooler that the injection would adjust for changes. I need to place a thermocouple under my engine cowl some time and see just what the under hood temps really are. Enough about my day dream.

On my car I used "shorty" headers, 1-5/8" primaries, to a 2-1/2" Y pipe, to a single cat (hollowed out admitedly), to a 3" single stainless steel cat back, through a single 1 in -> 2 out, straight through muffler, and two 2.5" tail pipes. At that power level, the exhaust was a restrictive element, but it was carried over from waaaaay back when it was the first mod to my original 170 hp TBI engine. If I had kept the car longer, it would have gotten 1-3/4 long tubes, dual 2.5" w/an X pipe, duel muffs, and dual tail pipes.

10-18-2004, 07:18 PM
What kind of car was it?

I would think that when the boat is moving at any speed, the motor would consume any hot air in the motor box and fresh, cooler air would displace that. With the vents and ducting to the front, unless it's heat soaking or idling, it may not get terribly hot under there. Cold air would be nice, though.

The IAT/recal yielded better hole shot, top end and economy to a MB Wakesetter and this guy boarded a lot with the Wedge and a lot of water for ballast. The recal enabled that input and included it in the program. He called down to Alan and asked if he had any programs and was told to bring it down during training since they already had some programs. They took it out on the water and acquired the data, did the recal, retested it once and they were done. We didn't do anything as far as cold air intake, though.

10-18-2004, 07:31 PM
That's sweet that the IAT netted tangable results. I'm plannign on a trip to Powell this coming weekend. Since this topic is at the front of my mind, I think I'll take my Snap-On DVOM and try the thermocouple and see. Your right that at speed, the engine should be inhaling a ton of air, and it should be fairly cool in there

But hole shot? After idling for 5 minutes waiting fro the next skier to get ready, take all the slack out of the rope etc by then the air under there has to be at least 120* I would think. I'm going to find out. You got me on a mission now! :)