i had 600hp to my boat spun the motor 5800rpm stock lines no good . put a a/f box on at idle was good put wot was running to lean . i was not getting the rigth amont of fuel . 8pd at idle 5pd wot .pull the plugs and see. or get a a/f box

I was talking about what the GPH is of those stock pumps that run off the water pump. If their like 80 that's not enough.

hi guys i see we are underway fully on this topic--now i will throw my 2 cents into it!!!:eek:

Pantera--your problem most likely lies in that the cam is too small and the heads dont flow. Anyone who suggested that you can use those oval port heads w success making close to 500hp is nuts! Also if you have a good Hi psi mechanical fuel pump and you have the vent trick done your fuel should be adequate, mech pumps can support a 700hp N/A motor.
I pm'd you also

I've read in mags before of people making over 500hp in 427's with peanut port heads. Large ovals will flow better than rectangle heads up to 5300rpm on a 454" motor. There's flow test all over the internet that show it. Don't know his exact cam specs but he has post it having .600" lift which should be plenty besides the fact it was custom designed by a very reputable source. All he needs is 7lbs. of fuel pressure. What he does need is high volume. Never heard of the fuel pump vent trick. Can you let us in on it?

The stock Merc seapump mounted fuel pump is 120-130 GPH.

i had eddie young make me a bigger tube for the gas tank put 1/2 in lines now my pressure at 8pds wot a/f 12,5 at 5700rpm and i have a holley pump. 3/8 is ok for 500hp but 600hp i go with 1/2 to be safe.

I ran the boat for the first time in a back canal I hit 5000 rpm and 67 with 23plus big diff from intercoastal running. The motor does get hesitation sometimes around 4000 rpm then starts pulln again,

Did you set your timing while at full advance? If so what did you set it at?

Approx 32 total advance, im going to try my old 23 labbed should geta lil more rpm, and i need to set up my a/f ratio in pipe.
What are you guys thinking the hp output should be on this motor with this setup?
Thanks

Did you get your fuel issue solved?

You need at least 36 total. I run mine at 38.

Can you run 89 octane so far advanced?
So when i advance it at the top is it ok with the bottom naturally advancing itself as well?

It runs up to WOT sometimes with no problem, it does choke for fuel sometimes if you try to do mulitple fast runs. So im going to check the tank pick up this week.

The spec in merc manuals for engines similar to yours (400-420-440-460) is 36 total. I would think they keep it a little conservative. It will be fine at idle as long as it's not more than about 15-16. Idle speed will pick up so you may have to idle down the carb. What's timing at idle now? What ignition setup do you have now? Should be fine on 89. I trailer mine so I always get 92-93 on the road before ramping in.

Thanks for the help..
Im running a new hei distibuter
I forgot initial ill check next time i fire it up.
I run high octane and mid grade depending on how week went lol.