502 MPI build up

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11-26-2018, 10:01 AM

#11

hogie roll

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The key differences are the heads, cam and exhaust. I believe the intake is the same.

525s have edelbrock heads. There are better aftermarket options. Cam is similar to crane 741 which is good for what you’re doing. You should skip the 525 exhaust and use the thunder n lightning.

11-26-2018, 11:22 AM

#12

Baja Rooster

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If you stray very far from stock add in another $1500+ or so for redoing the oil cooler and fuel systems. I’d freshen up the short block to marine specs, have some good heads built, massage the intake system, and enjoy boating for another decade or two.

11-26-2018, 11:39 AM

#13

BBYSTWY

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forged internals, cam, heads, prochager/whipple....done

oh yea and a pile of bravos to swap the broken ones lol

11-26-2018, 01:12 PM

#14

F-2 Speedy

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Quote:

Originally Posted by hogie roll

I suspect you could do it much cheaper.

Im talking about a custom built 540 and a Mercury 525 EFI not a 454 with a 525 sticker on it......you can always do it cheaper but how long will it last. good luck OP

11-27-2018, 11:01 AM

#15

Bang Bang

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without heads i would not get the 540hp, right?
As i asked... ( double 58mm trottle body, rip down the intake diverters, put in a 525 or similar cam, pistons wich add litte bit more compression rate (we have 95 fuel), a little porting, ecu reprograming ) what do you think i could get out of it?

11-27-2018, 11:04 AM

#16

articfriends

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I saw 560 hp in dyno trim from a 502 w modded intake, 68 mm tb, 731 cam and lots of tuning on 89 octane. Iron heads w mild porting. Tpis bores throttle body from twin 60 mm stock to 68 mm for 270$ btw

11-27-2018, 11:53 AM

#17

Bang Bang

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I saw the Tpis TB, thanks! Perhaps a friend can do this job for me. Did you use the original 088 heads or aftermarket?

11-27-2018, 12:07 PM

#18

Diamond Dave

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Quote:

Originally Posted by articfriends

How much did just the throttle body alter the tuning in your case I don't recall if you mentioned it specifically?

Last edited by Diamond Dave; 11-27-2018 at 12:27 PM.

11-27-2018, 01:02 PM

#19

Griff

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I would bet you will need at least 600hp to go from 70mph to 80mph

11-27-2018, 02:25 PM

#20

hogie roll

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Quote:

Originally Posted by Bang Bang

I saw the Tpis TB, thanks! Perhaps a friend can do this job for me. Did you use the original 088 heads or aftermarket?

make sure you understand the difference between dyno trim and in your boat. Highly dependent on your exhaust manifolds and how many pumps you hang off it.

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