Dmac88sport226

Hey guys, I'm dozing some mild work to my carb 454 mag. It's the original motor and I'm doing a 3 angle valve job a .218/.224 at .050 cam and probably a Hardin seaward series manifolds on it. Still going to use the stock aluminum intake manifold and might possibly change to either a edelbrock or quick fuel 750 cfm, not sure depends on the funds. So I was thinking of switching to a 4 blade prop and I always have people in the boat so I was curious on some opinions on pitch size. The wot on the mag is 5200 rpm and it came with a 27 pitch 3 blade but that won't come out of the hole to save its life with people in the boat withs full tank. Thanks guys.

class6

I would go with the Bravo1 24, Lose a little top end, but it going to be the best bet for everyday boating with people on board. Should come up on plane real good

Dmac88sport226

That's what's was thinking but aren't you supposed to go down 2" in pitch when you move to a 4 blade?

class6

Most 4 blades are even #s and 3 blades are odd #s in the bravos and Mirage. Step done to the next number when moving to a 4 Blade. But I think a 26 is too much. It might pull it, but id rather have the low end punch of the 24

getrdunn

iTrader: (7)

25 mirage

getrdunn

iTrader: (7)

I shoulda asked what your projecting hp is? Sounds like should be 365 plus.

Seems like that boat came with a 25p

Dmac88sport226

It's 365 stock but I think that was flywheel rated. So I'm hoping maybe 400. It had a 25 on it when I got it. But with like 3 people in the boat and I full tank it's a dog out of the hole.

SB

iTrader: (1)

If you have a 365 MAG, your cam choice may lose power.

Merc Mag Mark IV engines have the following flat tappet cam:

Mag BBC 454/502 Flat Tappet (rect heads)

.004” 296*, 296*
.006” 286*, 286*
.050” 224*, 224*
.200” 130*, 130*
Valve lift with 1.7 .510”, .510”
LSA 115.5
Merc Part#431-9830 / GM#14096209
ICL 114 ATDC
ECL 117 BTDC
=============================

For reference sakes, the carbureted 7.4L Merc 400 / 420 / 425 's
came with the following flat tappet cam:
Crane Part#132561 Grind # H-228/312-2S-14 T1.2
Duration at .004” : 298, 306
Duration at .050”: 228, 236
Lift with 1.7 rocker: .530”, .551”
LSA 114LSA
ICL 109 ATDC , ECL 119 BTDC

BenPerfected

You might want to talk to BBLADES about a 23P Mirage reworked to get you at the target RPM at WOT. It seems to me this would be better than the 25P getting on plane and you might not have to trade off any or much top end.

Dmac88sport226

It's .224/.224 @.050. I talked to cp performance they said .218/.224 @.050. The lsa is 112 stock to