Calling all Carb Gurus

I'm no guru, but I'm guessing the guys are gonna whip ya for using this in your boat.

I'd definitely start saving for a remanufactured marine carb.

Marine versions don't have floats that can be adjusted externally, certainly an automotive carb you have there. The marine carbs have a few extra seals and gaskets that the auto doesn't. Mainly to prevent you from exploding.

Thanks Brian! I ordered up the carb from National (via Ebay). Got it for $239 + shipping. Supposed to arrive this Friday. I'll post up some pics and a review once I get her bolted up. Hoping this cures my issues.

I thought the only difference in Auto vs Marine on most carbs was the vent tubes. The marine being "J" shaped and the auto being straight up.

Is there any truth to that statement Eric? or do you know of other differences?

Chris4x4gill2 wrote: I thought the only difference in Auto vs Marine on most carbs was the vent tubes. The marine being "J" shaped and the auto being straight up. Is there any truth to that statement Eric? or do you know of other differences?

No. the throttle shafts are sealed to keep fuel from seeping externally under flooding conditions.

Also, any 'universal' holley will never run the same as the application specific marine carb. The marine carbs and medium duty truck carbs, are designed internally for managing the best combustion temps and power under sustained high loads.

Therefore the PVCo's behind the PV are sized to be exacty 50% of the main jet size to deliver 25% more fuel under high load, for stoiciometrically correct a/f ratio under different conditions.

The PVCO's on the universal carb are way too big to keep amature hotrodders from fragging their engines and blaming holley. Thats one reason why they belch black when they stomp on it.

With a universal carb you can change jets all day and it wil still run like azz. Plus risk getting blown up.

Hmmm, very interesting reading guys. Thanks for all the responses! I bolted up the new carb (from National) and put about 6 hours on the boat yesterday. Still having major issues. The top end is vastly improved but the boat now dies completely when you punch it.
She idles great, and if you throttle up slowly runs up to about 1500rpm, then sputters and runs erratically up to about 2000. If you punch it at 2000 rpm, she screams up to 4000+ and 40+ mph easily. Accel pump seems to be shooting ok.
Have checked timing, set at 10 ATDC at idle. Advance does not seem to move at all until about 2000 rpm, and then creeps up about 15 degrees. I am thinking distributor is the issue now. Can these be taken apart and cleaned up, or should I just look into a new one.
Or do you guys still think I have carb issues? The only mystery to me on this new carb is that it has a tube that comes out above the secondary diaphragm, labeled "return to fuel pump". Not sure what that is all about, I have it capped off.
The new carb does have j-tubes and non-adjustable floats. BTW I now have a (possibly original?) Holley for sale!

The other thing I just noticed... your timing is at 10 ATDC? .. dont know a thing about the Ford...but,seems a little late? should it be somewhere BEFORE TDC?

I'd say your distributer is still compromising your boating experience.

25 degrees total advance is about 13 shy of optimal for a 302. You shoudl be at 25 degrees by around 2000.

Just get a new Mallory, i think you won't regret it.

Checked the firing order and it was good. Rechecked and measured timing and looks like I was getting even less advance than I thought. Only about 10 degrees.

Decided to pull the trigger on a YLM512CV Mallory from Summit, after doing a bunch of reading on here. Thanks to 79Nautique, TRBenj and others for all of the comments on other threads, very informative. I was tempted to go for the YLU optical pickup or performancedistributors.com DUI solution, but am feeling a little tapped out on the boat budget after the carb replacement. I can't afford to spend $350-400 on a distributor. Since this motor will be staying stock I just decided to go for the economical solution. Hopefully the advance will be right. Looks like I should have it for the weekend so we will see.

Thanks everyone for the help thus far. I am dying to get this boat running right. Took a ride in Mark Mel's boat last week and it just blew mine away out of the hole. It was like mine was running on 4 cylinders compared to his. Right now I can't even get up behind my boat on a slalom ski    Crossing my fingers this will solve the problem.

sorry, i read thru and see you tried it
have you done a comp test? or taken some vacuum readings?

At least the boat is running well enough to get up on my wakeboard:

Well, after replacing the distributor with no change I am back to the carb, specifically the accelerator pump. I tried a simple test on the lake today, opened the motorbox and had my buddy drive and hit it hard. Normally this kills the motor (still doing it today even with new dist and correct advance.)

However, while he hit it I pumped the accel pump linkage hard by hand. The boat blasted out of the hole like she should!!

I did some more fooling around and the boat actually screamed up to speed best if I pumped the accel pump linkage by hand twice quickly, once off idle and one again at 2000 or so rpm.

I am thinking I need a much more aggressive pump shot. I am running a size 25 nozzle(s) and the red cam. Thinking of going to a size 40 nozzle with hollow screw, 50cc pump and hotter cam (brown?). Bigger nozzle to get the shot in earlier (along with the cam), and larger pump size to hopefully keep a long duration on the shot.

What do you guys think? What are people running in terms of nozzles and pumps? Is the stock 30cc pump sufficient on these carbs?

I know this is a drastic change, but what I have right now is not just a stumble, the boat dies completely on acceleration every time if you hit it hard.

Thanks!!

if this helps I commited a sin, pcm 302, some of the problems i recently went thru. 2 firing orders they will run on either, 450 holley, rebuilt it and couldnt get the idle down under 1500    dumped it and put on a weber....
pulled the front cover and the chain was so stretched it was probably a couple of degrees out of time when in time and this was discovered after a fluctuating timing mark and a touch low on vacuum readings.
but the brunt of my problem was the stretched chain, she cracks now.....

eric lavine wrote: pulled the front cover and the chain was so stretched it was probably a couple of degrees out of time when in time and this was discovered after a fluctuating timing mark and a touch low on vacuum readings. but the brunt of my problem was the stretched chain, she cracks now.....

Eric I get shot down every time I mention a stretched chain on these things but it's not an urban legend. Direct from PCM tech support over 700 hours and it's a posiblilty for low power. I don't know why thats so hard to believe.