You can use the newer USCG rubber hose. You can find it in 1/2".

OK, then I'll go rubber up to the fuel/water filter, and then stainless and AN from there. That should save me a little bit.

Thanks for the help, guys. Have fun this weekend!

OK everyone, I need some educating. I understand how important it is to not run an engine lean due to an undersized fuel systems. But I have never changed my pickups,or up-sized hoses. I have gone from the Mercury sea/fuel pumps to electric Mallory 140GPH fuel pumps. Every winter I drain my tanks. I just unhook my fuel line from my fuel pressure regulator at my carb and turn on my fuel pump. I have timed it out and I can fill up a 5 gallon gas can in under 3 mins. That is almost 100 GPH actual gas the hose and my pickup can supply at free flow. I do understand free flow rates and that flow and pressure are inverse proportion and how to choose a fuel pump. But when it gets down to it by math, flow charts and actually filling gas cans, why can't a 3/8" hose support more than 500HP? I also understand that pickups and fuel lines are changed for electric pumps because it is important not to cavitate the pump and hurt it.

Wait till your stainless fuel line finds + battery terminal or a stray +12v wire that that got knocked loose in 3'-4's and is now glowing red hot in your bilge. I'm going to be changing out to rubber USCG rubber hose this year.

I had braided due that too me. Engine was running poorly. Noticed the fuel pressure was down a tad, so figured I'd adjust that first, until my elbow (same arm where my hand was grabbing theline and regulator) shot a inch or so long duration fat spark to the flame arrestor. Okay, it was a few sparks as I tried to move.

It hurt bad ! Thank god I didn't blow up.

Engine ground was bad, so I became a tad better ground.

Yikes !

A 3/8th's can move a bunch of fuel. Is sometimes enough for 500hp or more. But, it's getting close, so would never suggest it, especially when reaching 600hp or so.

That's all.

I'm confused. So are you saying to go with with rubber hose all the way up the the regulator or the carb? I was under the impression that rubber lines were not allowed between the pump and the carb by USCG regulations. All the factory Merc motors that I have seen had hard metal lines going up to the carb. Wouldn't these conduct just like the braided SS lines?

I also thought about using something like the push-lok hoses and fittings. Those are non-conducting, aren't they?

BSFC of 0.55 at 700HP = 385lb/hr fuel needed. 385lb / 7lbs/gal = 55 gallons/hr actual gas needed. I have extracted over 50 gallons out of my boat many times in less than an hour. I just don't understand what I'm missing.

I also am not recommending any hose size just trying to understand.

SB Not trying to argue or disagree. I know that some times conversational tone and inflection can not always be conveyed through written text. It's all good

The tubing is rigid and secured. I'm not saying you would run your fuel lines all half assed like I did. Not thinking of +12v sources. lol

For one you're missing the pump's flow curve - as pressure increases flow decreases. When you're dumping your boat there's no pressure to buck vs ~7psi for carb or 30-40-??? for EFI.