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Bajaorlando 05-12-2018 07:53 AM

502 build advise
 
Hello everyone
new to the forums
i searched the forums for answers before I posted so not to put up yet another build thread
to start I have a 2000 33 outlaw twin 502 mag mpiís that are stock
my thoughts are to pull the low hour mills and freshen up with a hone and rings and bearings on the bottom end. Then have heads checked and install inconels on the exhaust and springs to match the yet to be determined cam.
i am wanting a fairly mild 600ish hp and was leaning towards a 8/71 with twin 750ís along with manifolds like imco powerflows with risers. Forgot to add that the oil cooler will be upgraded. Boat has full hydraulic to the helm.
please share some of your experiences with a somewhat budget build along with doís and donít
Thanks in advance

hogie roll 05-12-2018 01:07 PM

An 871 could make up to 800hp. You could make 600hp easy with new heads like Brodix dragon slayers 320 or promax 317s with a 741 cam and good exhaust.

F-2 Speedy 05-12-2018 01:25 PM

If you cant do a bunch of this work yourself, you could easily spend 20-30k to get this done...........I had the same power and boat at one time

Bajaorlando 05-12-2018 06:23 PM

I do plan on doing all the work myself with the exception of machine work. I will buy my own pieces.

Bajaorlando 05-12-2018 06:25 PM

Was just hoping for some real world examples of similar builds. My biggest questions are cam and exhaust and how much boost with the iron heads and the mag pistons

Baja Rooster 05-12-2018 07:55 PM

My recommendation would be to leave well enough alone. If you canít do that then buy some already made power out of the swap shop here as thereís a multitude of reputable sellers here and sell the stock power for a pretty penny. If you canít do that then call Eddie Young who is incredibly helpful to the community will save you literally boat loads of grief and money.

600hp is commonly attained with some good heads and Crane 168741 cam, and your Bravo drives may actually live through the summer.

You should actually call Eddie first and he can answer what youíre looking for.

hogie roll 05-13-2018 08:15 AM


Originally Posted by Bajaorlando (Post 4626087)
Was just hoping for some real world examples of similar builds. My biggest questions are cam and exhaust and how much boost with the iron heads and the mag pistons

I think stock CR is 8.75. You could run maybe 7psi non intercooled on an 8-71 with that. Exhaust you should check out the thunder n lightning cast aluminum. Dry to tip tails will let you get aggressive with the cam. Most people like the 741 cam, it is the 525 efi cam I believe, or similar. That combo would make 700-800hp depending on cam and boost.

Bajaorlando 05-14-2018 06:52 AM

Thanks Hogie
what are the rest of the numbers on that cam
Will it work with my GM lifters?

convincor 05-14-2018 08:05 AM

Crane 168741, and you need lifters as well. 13532-16

Bajaorlando 05-14-2018 08:08 AM

Thank you

Crude Intentions 05-14-2018 08:17 AM

I have builds similar to what you're looking for. You don't need blowers for 600. Your basic combo with 8-71s will be 800+. I have a comp custom cam. EQ heads with no port work just bowls cleaned up and a good valve job. 8.7:1 compression. Merlin intakes. 2 1 inch spacer and quick fuel 850s. 570 on the dyno in marine trim with wet exhaust. This was through etops. With some longer runners like CMI sweepers or eickerts these would have been 600 no doubt.

Bajaorlando 05-14-2018 08:21 AM

Thanks Crude
what comp cam do you have?I have not heard of eq heads are they iron?

hogie roll 05-14-2018 08:51 AM


Originally Posted by Bajaorlando (Post 4626331)
Thanks Hogie
what are the rest of the numbers on that cam
Will it work with my GM lifters?

search function

Crude Intentions 05-14-2018 09:14 AM


Originally Posted by Bajaorlando (Post 4626346)
Thanks Crude
what comp cam do you have?I have not heard of eq heads are they iron?

yes they are iron. Flow very well from the box and very cost effective. It's a custom cam off their huc lobe series. 243/251 .627/.632 on a 112.

Crude Intentions 05-14-2018 09:16 AM

Also went with Johnson lifters. Eddie young advised on these. Ferria valves. Isky springs. Double roller timing chain.

hogie roll 05-14-2018 10:33 AM


Originally Posted by Bajaorlando (Post 4626346)
Thanks Crude
what comp cam do you have?I have not heard of eq heads are they iron?

engine quest. Most find it practical to buy new heads instead of rebuilding since it doesnít cost much more and you get more performance. Unless you have your own rebuilding capability, free time, and are really pinching pennys rebuilding doesnít make sense.

Bajaorlando 05-14-2018 10:44 AM

Crude
Did you buy them bare or assembled? Are you running stainless intake and iconel exhaust
what rpm you spinning and how much timing?Sorry for all the questions but I really like the simplicity of a single carb setup.

Crude Intentions 05-14-2018 01:22 PM

Bare. Had my guy go through them. Never buy assembled. Production stuff doesn't get the attention it should. I used ferrea super alloy exhaust valves. Ferrea competition stainless intake. .135 wall pushrods. Valve train is the key to longevity and reliability. [email protected] Again. I know for a fact I'm choking myself with exhaust. Gonna be upgrading that next year and dynoing again.

Bajaorlando 05-14-2018 01:37 PM

Great advise and thanks for sharing it is much appreciated

RaceRPM 05-15-2018 09:08 AM

Another option is to call Bill at Ateco Marine. He has various upgrade packages for the 502 MPI. Mine are now 540's with Dart Pro 1 heads and made 630hp at 5300rpm's using the merc mpi intake and fuel injection system (MEFI 3). They look like stock 502 mpi's, but boat runs about 10mph faster and they idle like stock motors as well. Third year and 80+ hours on the motors and very happy.

Bajaorlando 05-15-2018 10:15 AM

What did the upgrade cost you racerpm?

F-2 Speedy 05-15-2018 10:53 AM


Originally Posted by RaceRPM (Post 4626602)
Another option is to call Bill at Ateco Marine. He has various upgrade packages for the 502 MPI. Mine are now 540's with Dart Pro 1 heads and made 630hp at 5300rpm's using the merc mpi intake and fuel injection system (MEFI 3). They look like stock 502 mpi's, but boat runs about 10mph faster and they idle like stock motors as well. Third year and 80+ hours on the motors and very happy.

whats the cam specs and pistons that are in these, can you post the dyno sheet...........4.500 X 4.25 X 6.385 is this the combo that they use to get to 540cu in

RaceRPM 05-18-2018 08:48 AM

Cam is .632 and .632 lift on 114 center, pistons are SRP dome top +10cc. Have dyno sheets but need to find them, actually went to the shop and witnessed a few dyno runs. Yes 540ci with rods 6.385, bore is 4.500 and stroke is 4.250.

RaceRPM 05-18-2018 08:50 AM


Originally Posted by Bajaorlando (Post 4626620)
What did the upgrade cost you racerpm?

I will PM you the details.

Bajaorlando 05-22-2018 06:46 AM

After reading countless articles and contributions from various forums, my goal is to be slightly over 500hp. I know I do not have the pocket depth to build a 90+ mph boat so I decided to stay mostly stock. I plan on keeping the heads and rotating assembly stock. I want to add a cam and cmi's The opinions on cams is all over the place. So the last 2 pieces of the puzzle are cam and someone who can program my ECU to match the upgraded exhaust and cam. Any Ideas? I appreciate everyone's input it is appreciated .

fastlane40 05-22-2018 01:49 PM

Crane 168741.Or if you want to tone it down a bit a crane 731.I have 2 of them out of 500 EFI's if your interested $250 our money about $200 in yours plus shipping.
Quite a few in your part of the world to do your ECU.Google.


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