Did you check your vacuum plugs on the throttle plate? Make sure 1 isn't cracked or missing.

Set your timing using and adjustable gun and set it at full advance to be certain you have it right on top. That is much more important than initial. Set your gun at desired timing. probably 30 in your case, and rev the engine until the mark quits moving, then move the dist back to where the marks are at 0 and you will have it right.

Good luck

This is what I have in my Barry Grant (Holley) 750 DP's in my Merc 425's:

The butterfly's have 172 stamped on them, powervalves are 6-5's, 30cc accel. pump, jets are: Front 77's and rear 87's.

You shouldn't need more than that. WATCH your plug readings!

Check the float level, it should be at the bottom of the sight hole when running. Sounds like the level is too high and the fuel is spilling out of the bowl at idle.

i got her to idle down to 750 today , but she's still popping when you first hit the accel pumps , primary and secondary
i havent checked the float levels cause she's still on the trailer and the boat sits at a much different level when its in the water
i have a rebuild kit that will be to me on friday , and i'm pretty sure it wont be too hard to rebuild the carb
and install jets/power valves as long as it hasnt been drilled on , if it has then i'm just buying a new edlebrock 750 marine and done with it
hopefully i can re-build this one , beer money is gettin scarse

ok , update

I'm in the middle of re-building my holley 750 double pumper
the jets that are in it are 70 primary and 80 secondary's
seems close e-nuff to try right?

heres the real head scratcher
it only has 1 power valve , and its marked 0-5
on the secondary side there was a solid power valve (no valve) threaded in , and from looking at the bottem side of the carb , its not drilled for the vacuem to reach the valve
am i missing something?

Your missing some numbers on the power valve, keep looking. It's probably a 6.5. Yes, you only get one valve in the front. That is why the rear jetting is so much larger than the front. It for ecomony when you are cruising. With the jets I would go to 75p, 85s and assume the 70/80 is box stock. You really should find out what stock is and adjust up 5 jet sizes. But guessing might work too. I think what is in there now is too lean.

The pop sounds like a lean pop. Make sure the accelerator pump in the primary is working. Sounds like it is not. Look down the throttle bores and actuate the throttle and make sure there is a solid double stream of fuel spraying in. Also, check the float level. It will be close enough vs in water. You can do it again later. Also look down the venturis when it is running and make sure fuel is not dripping out the boosters. Thats a sure sign the float level is too high or there is debris in the needle/seat.

BT :cool-smiley-011:

during the re-build i put a 6-5 power valve in the front and re-installed the power vavle blocker in the secondary (since there was no vacuem going to it anyway)
i set the float levels (gotta re-do it on the water again) and she seems to be idling fine now
there is a big hesitation when you crank the throttle open fast . but that could be the old wires and plugs in it , thats the next step
i'm just worried as hell about running lean and blowing this thing up , its been alot of hours putting it together
too bad the weather is sucking butt here in the east , i might have got some testing time in

Check your timing at full advance. Make sure you are advancing properly and to the right timing. I wouldn't run that engine past 30-31 total. Don't set it at idle and try to do the math, better to rev it up and make sure, for right now.

Also make sure your valves are adjusted properly. And check your accelerator pumps.

my timing light is a K-mart special , but my boss at work has the nice Snap-on , so i'll borrow that one monday and set the timing for 30 degrees at 3000 rpm's

aside from the basic gear lube and tune up crap , i think i'm water ready , time to get a baseline with the 15x23 prop i got now and decide how many inches i need to go up to get a nice balence of top end and out the hole , i'm thinking a 36 pitch 5-blade , or maybe just a mirage plus 25 or 26 :D

Yea that 36p 5blade should be a rocket out of the hole. :)

Double check that accelerator pump. You should be able to tune out the hesitation when you punch it.


Darrell.