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502 Mag MPI HP upgrade question

Old 01-11-2012, 02:08 PM
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Originally Posted by Poker~N~Run
Efi system is worth a few hundred in real money. Msd 6al ignition box can be bought from summit. Usually can find on Craigslist cheap. Same with dist. I would do it now and enjoy. All compatible with a cam change later.
Just out of curiosity, would there be any benefit in changing the rest of the ignition system? Like a new distributor and coil? Or would the MSD 6M2 ingnition box be enough? Also, would I need a new fuel pump and regulator?

Last edited by MCKILLOP; 01-11-2012 at 03:52 PM.
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Old 01-11-2012, 03:51 PM
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One more question for you guys, I know its impossible to say exactly, but any idea what kind of HP gains I could expect if I swapped out my EFI for the dual-plane RPM intake and an 800 or 850 carb and an HP 500 flame arrestor? I already have the Gill Offshore exhaust and would also be doing an MSD ignition setup and possibly a fuel pump and regulator if needed?

Last edited by MCKILLOP; 01-11-2012 at 03:58 PM.
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Old 01-11-2012, 04:25 PM
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Old 01-11-2012, 07:59 PM
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I got your message, I sent you one back with my email address.


Originally Posted by MCKILLOP
One more question for you guys, I know its impossible to say exactly, but any idea what kind of HP gains I could expect if I swapped out my EFI for the dual-plane RPM intake and an 800 or 850 carb and an HP 500 flame arrestor? I already have the Gill Offshore exhaust and would also be doing an MSD ignition setup and possibly a fuel pump and regulator if needed?
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Old 01-12-2012, 12:54 AM
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Originally Posted by MCKILLOP
I am starting to put together a new boat and am trying to do it on a budget while getting every mph possible. I am wondering what, if any HP upgrades that can be done with the motor in the boat? I recently picked up some Gill Offshore wet manifolds with stainless risers, a K&N flame arrestor, an adjustable fuel pressure regulator and will soon be ordering a Mark Boos ECM tune and upgrading my B1 to a BX1. Is there anything else that would be worth doing with the engine still in the boat? I would love a Procharger, but dont really want to dump that much money into a starter boat. Like I mentioned, I have no reason, nor funds to pull the motor this year so a new cam is out of the question for now. Any other options out there for a few extra mph?
All the upgrades you posted might be good for 1-2mph, if you're lucky. Better off to just get your prop labbed and put the rest of the $$ in the fuel tank.
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Old 01-12-2012, 08:38 AM
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Originally Posted by Griff
All the upgrades you posted might be good for 1-2mph, if you're lucky. Better off to just get your prop labbed and put the rest of the $$ in the fuel tank.
+1

I wouldn't do anything until you can do a cam, well, installing the headers is ok since you already have them...I basically built the carb combination others are talking about here last summer.

For reference here is the carbed combination I had assembled this year.

- Stainless Marine Manifolds (these were already on the boat)
- Rectangle heads with stock valve size and a valve job (matched to intake NOT ported) with Performer RPM (rectangle port air gap) intake and 850 Holley 80330 vacuum secondaries, one jet size down on secondaries
- Converted Gen V 502 Block to roller, honed only not bored -- Bob Madera (RMBuilder) Custom Cam
- Stock JE700 pistons with new rings, stock rods.
- 9.25:1 compression up from 8.75 (.010 off the block and .010 off the heads)
- 1.7:1 Scorpion Roller Rockers

539HP and 569TQ full dress with wet exhaust. Peak power was ~5100

I am sure I left some power on the table -- I specifically told Bob this was a family boat and drive-ability and good idle characteristics were the priority -- he is the man and should be your FIRST phone call, he was EXTREMELY willing to work with me to get the RIGHT combination.

Last edited by brivander; 01-12-2012 at 08:44 AM.
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Old 01-12-2012, 11:58 AM
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Originally Posted by brivander
+1

I wouldn't do anything until you can do a cam, well, installing the headers is ok since you already have them...I basically built the carb combination others are talking about here last summer.

For reference here is the carbed combination I had assembled this year.

- Stainless Marine Manifolds (these were already on the boat)
- Rectangle heads with stock valve size and a valve job (matched to intake NOT ported) with Performer RPM (rectangle port air gap) intake and 850 Holley 80330 vacuum secondaries, one jet size down on secondaries
- Converted Gen V 502 Block to roller, honed only not bored -- Bob Madera (RMBuilder) Custom Cam
- Stock JE700 pistons with new rings, stock rods.
- 9.25:1 compression up from 8.75 (.010 off the block and .010 off the heads)
- 1.7:1 Scorpion Roller Rockers

539HP and 569TQ full dress with wet exhaust. Peak power was ~5100

I am sure I left some power on the table -- I specifically told Bob this was a family boat and drive-ability and good idle characteristics were the priority -- he is the man and should be your FIRST phone call, he was EXTREMELY willing to work with me to get the RIGHT combination.
Thanks for the advice guys. I think I already knew the answer that question, but was hoping I might be wrong. I have decided to keep the EFI and save my money for a Procharger set up.
Thansk again for the advice, I really appreaite it.
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Old 01-12-2012, 12:17 PM
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If your motor is running ok then don't do a thing to it. Do not pull the efi. On that type of boat you will do a lot of 2500 3500 cruising and the carb will will prob cut your fuel economy in half. Dumb move. 2 options for speed. 1 have your prop labbed.. Cost is like 400. Speed gain on that boat prob 2 mph. Next is Sell your motor for prob 5000.00 Buy a used 525 for maybe 15000 plus a prop 500. 00. Maybe get 10mph. If your lucky find a used prop for the 525 and have it labbed . 650 total then your up to 13mph for a total out of pocket of 10650.00. These numbers are for example but not too far off. If I were you I think I would go the 400.00 route.

Chris


Originally Posted by MCKILLOP
One more question for you guys, I know its impossible to say exactly, but any idea what kind of HP gains I could expect if I swapped out my EFI for the dual-plane RPM intake and an 800 or 850 carb and an HP 500 flame arrestor? I already have the Gill Offshore exhaust and would also be doing an MSD ignition setup and possibly a fuel pump and regulator if needed?
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Old 01-12-2012, 02:38 PM
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I also vote for keeping the EFI. When you pull the engine you could swap the cam for a 500EFI cam(or similar) and adjustable roller rockers. Then get the ecm tuned while running the boat. That would be a nice bump in HP.

Last edited by onesickpantera; 01-12-2012 at 02:42 PM.
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Old 01-12-2012, 02:48 PM
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Forget about making the boat go faster,Spend the money on beer and broads


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