Considering going from 500 efi to intakes and carbs
10-05-2025 | 09:52 AM
#11
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From: Lake Ozark, MO USA
Are you running electric fuel pumps on these? If so, can you post up some pics of fuel system and what all you did. TIA, beautiful work!
10-06-2025 | 11:23 AM
#12
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From: BC
Or better yet, have a 3rd pump as an emergency pump that is self pressure regulated.
You may not get full flow for WOT, but the intent is to be able to cruise and get home.
Filtered fuel to the pumps, mounted to reduce lift to the pump.
10-06-2025 | 02:25 PM
#13
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From: Merritt Island, FL
That was crazy.
Seafoam or Lucus injector cleaner.
BTW you posted a Oval port intake, HP500EFI's are rectangular port.
10-06-2025 | 03:12 PM
#14
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From: SWFL
Articfriends is correct. I have HP500EFI's and just use injector cleaner every other tank of fuel. They have around 780 hours on the motors and run great.
My engine builder (RIP) had a combo where he used the stock intakes with a 540 cu in kit and out of the box AFR heads. The thing had 700LB of TQ at 3500 rpm and made about 640 HP. That is some killer TQ for a NA motor and what we need most of the time.
You can seek higher HP but those intakes unless modified are not good at it and you normally lose low end TQ.
It's not a race boat.
My engine builder (RIP) had a combo where he used the stock intakes with a 540 cu in kit and out of the box AFR heads. The thing had 700LB of TQ at 3500 rpm and made about 640 HP. That is some killer TQ for a NA motor and what we need most of the time.
You can seek higher HP but those intakes unless modified are not good at it and you normally lose low end TQ.
It's not a race boat.
Originally had 540 with 502 mpi intakes, 308 darts and tuned computers, was a bear to 3500 where it would hit a wall and lay over, I'm guessing the intake/cam combo was an issue. I bought the boat that way.
Last edited by Sonic30ss; 10-06-2025 at 03:19 PM.
10-07-2025 | 08:10 AM
#15
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From: Merritt Island, FL
I make the same #'s with 540, Dart 308 iron head, 525 efi cam, Bill Mitchell single plane intake, 850 QF carbs, 1'' carb spacer, DUI ignition, Tq is 700 @ 3900 & HP 638 @ 5200.
Originally had 540 with 502 mpi intakes, 308 darts and tuned computers, was a bear to 3500 where it would hit a wall and lay over, I'm guessing the intake/cam combo was an issue. I bought the boat that way.
Originally had 540 with 502 mpi intakes, 308 darts and tuned computers, was a bear to 3500 where it would hit a wall and lay over, I'm guessing the intake/cam combo was an issue. I bought the boat that way.
I guess it comes down to if the OP wants to spend money on new intakes, carbs etc. Or just use what he has. Of course the 540 I talked about had different injector so took care of that. Options, Options.
10-07-2025 | 08:21 AM
#17
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From: East Coast
no I’m using mercurys setup that the later model 500 efi used as a lift pump to get fuel to the electric pump. They are mechanical pumps.
