Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Follow us on Facebook Follow us on Twitter
Results 1 to 10 of 10
  1. #1
    Registered formula271's Avatar
    My Boats:
    1999 Formula 271
    Join Date
    Aug 2001
    Location
    Oswego,New York
    Posts
    157

    502 MPI Upgrades

    Has anybody done any upgrades to these 502 MPI motors? I have had my ecm reprogramed and changed to a K&N filter which gained me a little more power. What about changing and/or modifying the heads, cam or intake? If so what heads or cam do you guys think will be the best to go with? What kind of cost are these upgrades going to be? No, I don't want to Whipple it or procharge it. I'm just looking to make another 50 or so hp. What is the difference between the 500hp and the 502 MPI besides about 55 hp? Thanks for any constructive input.

  2. #2
    I hate the winter!! Platinum Member Vinny P's Avatar
    My Boats:
    99 checkmate 259
    Join Date
    Jul 2001
    Location
    long island, new york
    Posts
    2,701
    I was kicking this same ideas around for a while. After hearing of a few horror stories of inproperly re-mapped E.C.U.'s I decided against it. Someone on this board sent me this link to an article that did just what you want to do. http://www.azspeed-marine.com/articles-1a.html It sounds great, really an easy thing to do. BUT, if a few guys here on OSO can give you some of their stories, you may think twice about it. If you can get a hold of DirtLawyer, he can tell you of his problems.
    My answer to the need for a little more power was finding an HP500EFI. I should have it delivered in a few days. I am not expecting a BIG increase in speed, but it will give me the 85 horsepower that I wanted to get from my 454 Magnum. Also, if you were to sell your 502 and couple that money with what the upgrades would cost, you can probably find a used HP500 for the same money. That way you increase the value of your boat, those Blue motors are worth something at resale.

  3. #3
    Registered
    My Boats:
    1986 Cigarette
    Join Date
    Oct 2000
    Location
    Knoxville,TN, USA
    Posts
    350

    502 MPI upgrades

    Upgrades are straightforward and work extremely well for this engine. These upgrades are well documented and are widely available from reliable and reputable engine builders. There are several people with lot's of history in successful 502 MPI upgrades. Cam, lifters, roller rockers with screw in studs added, valve upgrades, ECM reprogramming, exhaust, and minor head work are the most common things I've seen. Additionally a .005 bore with J&E pistons with improved ring operation is a nice addition.

    My word of advice. Only do these things with dyno tuning. You are just guessing otherwise. ECM programming is best left to those with experience.

    If you are serious about making these upgrades call Performance Marine in Oshkosh Wis. Ask for Rod. He can make these motors work very well.

    Good luck.

  4. #4
    I hate the winter!! Platinum Member Vinny P's Avatar
    My Boats:
    99 checkmate 259
    Join Date
    Jul 2001
    Location
    long island, new york
    Posts
    2,701
    You are right boatmon. Re-mapping an ecu should only be done on a dyno. I don't see how companies out there can say that they can get it right by just talking to you on the phone for a few minutes. I just feel that by the time you count up how much it costs to upgrade an engine right, you can step up to a better Mercruiser motor where you know it is right.

  5. #5
    Registered
    My Boats:
    1986 Cigarette
    Join Date
    Oct 2000
    Location
    Knoxville,TN, USA
    Posts
    350

    502 MPI upgrades

    I kind of agree Checkmate. But, there are tons of 502 MPI/EFI available and they share many of the good parts from the HP 500 series. There are good used 502 EFI's available for around 5K. I would say with the upgrades I stated, you could spend another $3-5000.00 and have a great performing motor. Personally, I like the fuel injection systems for idle characteristics and good mid range torque. Like you said, maybe getting a good used HP 500 is better. But, maybe not. Both are good motors.

    As for the flame arrestor/ECM upgrades, I've not heard any really strong user support. How about you ?

  6. #6
    hauling ass-a
    Guest
    Was just wondering, what horror stories are you talking about? I 'am running a arizona speed ecu and really have had no problems at all! Please fill me in dirty lawyer.

  7. #7
    hauling ass-a
    Guest
    Was just wondering, what horror stories are you talking about? I 'am running a arizona speed ecu and really have had no problems at all! Please fill me in dirty lawyer.

  8. #8
    Registered Cattitude's Avatar
    My Boats:
    '02 Daytona 30
    Join Date
    Jun 2001
    Location
    Lowell, Arkansas, Beaver Lake
    Posts
    1,210

    It's all in fesibility and expectations

    Lot's of options- spend a grand on ECU and flame arrestor for a GPS digit or two, Whipples on the other end. The middle ground may be viable if you are going to freshen the motor anyway. Otherwise you are spending on labor and goodies almost as much as a whipple for about 1/3 of the gain.

    The HP500 swap is viable if you can cut the right deals, does add nicely to eye candy and resale.

    Good luck!

  9. #9
    I hate the winter!! Platinum Member Vinny P's Avatar
    My Boats:
    99 checkmate 259
    Join Date
    Jul 2001
    Location
    long island, new york
    Posts
    2,701
    Hauling-ass:

    Is that motor you are running stock or modified? I was considering doing a little work, such as heads, valves,cam, bumping the compression just a bit. With this in mind, enter e.c.u re-mapping. I can get the motor to make a little more power with no real trouble, but all of this hinges on the re-mapped e.c.u. I personnaly don't see how someone half way across the country can do the right job by just asking you a few questions on the phone. Every motor I have ever built always requires some tuning. Most importantly MIXTURE. In a carb, no problem screw in another jet, or power valve. What do you do with EFI? Do you send the ecu back a few more times until it is right? I didn't feel like getting involved with that. What really made my mind up is when I called a company that does ecu re-mapping and asked what they do to the program to make power in stock motors, they told me that they lean out the mixture, and increase timing advance. So I asked him how does ADVANCING the timing, and leaning out the mixture bring you more top end power? He told me that is how motors would react to that kind of change. SO, I laughed in his face and hung up the phone. Now maybe I spoke to someone who usually cleans the bathrooms and was walking by the phone when it rang, I really don't know. In any case, I stick with my original thoughts, a modified motor should only have the ecu re-mapped on a dyno, where conditions could be properly monitored and the ecu can be set up according to the data.

  10. #10
    hauling ass-a
    Guest
    my motor is a 502 and it is stock. After talking with a few people about this issue I have come up with a conclusion about the ecu re-mapping. With my motor I did not re-map to gain top speed, I was told this change would only effect the low end and midrange. I have had no problems at all, my midrang was the biggest improvment! After talking with arizona speed they told me mercruiser loads up their lower end and has a little less timing advance. If you are looking to gain major improvements on the top end this would be a waste of money. I actually bought my re-mapper ecu of the classifed section of oso. I figured for $400 I got another ecu reprogrammed from arizona and if it didn't work I would have a spare to compare it with. Efi motors are fun to try and get big power without doing all kinds of mods. Personally if I knew I was going to keep this boat for 5 more years I would have whipple charged it!!!!! I still think you can't beat the whipple!!!


Similar Threads

  1. 4.3l mpi upgrades
    By Jean-Claude in forum General Q & A
    Replies: 2
    Last Post: 05-26-2007, 06:07 AM
  2. 6.2 MPI upgrades...
    By gferdon in forum General Q & A
    Replies: 8
    Last Post: 01-11-2004, 05:23 PM
  3. 502 mpi head upgrades
    By hauling ass-a in forum General Q & A
    Replies: 4
    Last Post: 09-12-2003, 09:49 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
OSO Sponsor
OSO Advertisers


OSO Directory
All times are GMT -5. The time now is 01:02 PM.
Powered by vBulletin® Version 4.2.0
Copyright © 2014 vBulletin Solutions, Inc. All rights reserved.
Search Engine Optimization by vBSEO 3.6.1
Original Poster In Postbit provided by Original Poster In Postbit v1.0.0 (Free) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
Copyright 2011 OffShoreOnly. All rights reserved.