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View Full Version : 502EFI Power/Speed Tricks



SupriseSuprise
01-03-2002, 07:02 AM
I recently purchased 272 Baja powered by 502EFI. I want more top end!!! The boat is completely stock and has only (95) engine hrs. Where is $2,000 best spent??

Tinkerboater
01-04-2002, 12:57 PM
The first thing to do is upgrade you exhaust then get your computer reprogramed to allow mods.

SupriseSuprise
01-04-2002, 01:04 PM
Tinkerboater, do you have any suggestions on particular header systems and is MSD the choice for the electronic's. I was looking into a package from Vortec called their EFI POWER PACK. It supplies a MSD programed EFI and comes with their flame arrestor kit.

Tinkerboater
01-04-2002, 08:45 PM
The merc ignition works just fine just get the computer reprogramed to allow for mods.I like the lightning headers I've had 3 sets so far on two different boats. Just use the stock electronics. Put your money into parts that will get you some real HP. New cam, head work, roller lifters. And yes get a bigger flame arrester. What prop are you running. One thing that works well is lab finishing but you dont want to hit anything and you have to be very careful when people swim near the prop because it is VERY sharp. Lab finishing the prop will usually get you 2 to 3 mph.
[This message has been edited by Tinkerboater (edited January 04, 2002).]

SupriseSuprise
01-07-2002, 02:55 PM
Tinkerboater,
Re Prop selections, I only have the 1995 23degree Mirage which came with the boat. Do you have a any particular source you like and what manufacturer have you had best of luck with? I am thinking a new mirage plus and maybe up 2 degrees.

upchurch@bbdlaw
01-07-2002, 04:27 PM
Tinkerboate...
Your claim that a "lab" prop will produce 2-3 MPH is interesting, but everybody brags about "their" product. Do you have DATA / experience???
I run a BAJA Outlaw 240 - 502 EFI - 66 MPH on the Gaffrig guage - which my GPS sez is "dead on".
Another 2-3mph would put me back in touch with a buddy that "out spent me" on his motor work last year. His 235 is knocking at the door (70 - GPS confirmed).
Who does this "lab" work and at what cost?
Maverick

Tinkerboater
01-07-2002, 07:16 PM
Sent you an e- mail. I had merc. do my 26" bravo 1's. I gained 300 rpm at WOT and gained about 3 mph. Cost was $350 each. Just be very careful because the prop will be very sharp. Also you will have to be more careful because the prop will be damaged easier from the thinner blades. Just remember that you have a rev. limiter to deal with. If your 100 rpm below the set point your not going to see 300 rpm increase only 100. So go to a bigger prop in pitch. And stay away from the 4 blade props unless you have a problem with blowout on take off. The 4 blade prop will be about 3 mph slower than a 3 blade prop. with the same pitch.
[This message has been edited by Tinkerboater (edited January 07, 2002).]

Tinkerboater
01-07-2002, 07:31 PM
Suprise - Do the headers and the 25 pitch mirage prop and your rpm should stay about the same as it is now. Mind you as long as your proped right now for the hp you have. I can't estimate what gain you will get without knowing alot more about you boat.(rpm at WOT / speed gps.) You will need to get your MERC. ignition reprogramed.

upchurch@bbdlaw
01-08-2002, 03:33 PM
Originally posted by Tinkerboater:
The merc ignition works just fine just get the computer reprogramed to allow for mods.I like the lightning headers I've had 3 sets so far on two different boats. Just use the stock electronics. Put your money into parts that will get you some real HP. New cam, head work, roller lifters. And yes get a bigger flame arrester. What prop are you running. One thing that works well is lab finishing but you dont want to hit anything and you have to be very careful when people swim near the prop because it is VERY sharp. Lab finishing the prop will usually get you 2 to 3 mph.
[This message has been edited by Tinkerboater (edited January 04, 2002).]
What is your recommendation on the Hardin/Marine 502 Flame arrestor w/ the "air straightner" behind the arrestor and ahead of the butterflies? With a Crane 13 HR 00078 and more fuel from the computer, will the arrestor make more speed? If so, how much, and does stock exhaust kill the effort?

Tinkerboater
01-09-2002, 09:02 PM
Just about anything that increases airflow increases hp. Haven't seen that flame arrester but I think I would stick with the k+n offerings. Decreasing airflow resistance from one end of the motor to the other is the secret to creating max hp. But everything has to balance. Small changes make small hp changes. You probably wouldnt notice any change with just the flame arrester. As far as straighteners I think most of that is just bs. A good way to see if you have an airflow problem is to raise your engine cover at top speed just an inch or two max speed (be very carefull it doesnt blow off) should tie it down so it can't. Dont try this in rough water. This works well for me. Can't seem to get the nerve to cut more ventilation into the sides of my hull. Getting rid of the stock exhaust is the starting point. Everything else comes later.