fuel line size?

[crankn101]

Sorry for the DUM question.

What size fuel line for a merc EFI?

200 HP 1998

I believe it's 3/8" but it might change to 5/16" somewhere and I don't remember.

Thanks

[1954bmw]

now the size battle starts

[rgsauger]

Can't go wrong with 3/8

[tux974]

now the size battle starts

LOL.....

Even though 3/8" will not hurt Mercury prefer for you to run 5/16" for a reason, even on a 300X which is a thirsty bugger. They even do not suggest an onboard filter if you have a spin-on on the motor........
To me it makes sense since a good flowing 5/16" is plenty and the pump will not need to work as hard.

[Chaz]

The biggest detriment to 5/16" hose is that the fittings have a 3/16" I.D. @ best. Some even smaller. It "costs" aprox. 1 PSI to lift water 1 ft. Most gas weighs .7 of water, so the numbers are a little better. So the little pulse pump that could, must lift an average of 3 to 4 feet. It's easy to see that by adding extra restriction, like an in line filter , or the weight of another 1/16" inch of line diameter .. would put that poor little square block over the edge.
The Hi-perf 260 - 280 horse 2.5 L motors came with a external pump for a reason. Sweeping bends, Large ID fittings .. no restrictions to flow vs demand.
The 300x is said to make 330 HP. 90% of the reason people say .. "Ohh them things all blow up" is the lack of fuel system they came with. Small line, pulse pump, single needle and seat in the VST , small area for the Hi-Pressure pump to draw from. They have to be a deadheaded system, there is little to nothing left over to return @ WOT.
A 500 cc injector running @ .85% duty cycle is 425cc min. X 6 = 2550 cc min X 60 = 153,0000 cc or 40.41 gal/ hr.
At 4 - 5 PSI , your not going to move most of a 55 gal drum in an hours time thru such a kinked up system with such little holes …
The little stuff is fine for cruzin around at part throttle, or 100% stock low output motors. But if your going to start makin power , the fuel system is the first thing that should get upgraded. Or you can wait till it starts burnin aluminum for fuel, It'z them dern Wiseco's … that oil yur a usin .. get some of that "white gas" an it won't a happen to ya … LOL

Like my buoy Steve says, properly sized ( big) … If he had started choking down his fitting size, it would have had an effect on mass flow.
Steve, take off that Rolex before putting your hands in that $hiz ..



I don't think a basic 2-stroke burns as clean as .6 (which is pretty dirty by 4 stroke standards) I would say it's closer to .7

330 HP / 6 injectors / B.S.F.C. .6 / 80% duty cycle / = 433.1 cc

https://www.witchhunter.com/injectorcalc1.php

Just my .02c

[crankn101]

Thanks guys. I really appreciate it.

[tux974]

~How can you dispute that much data..................................................................................
~I say according to that much data one needs to run a 1” garden hose............................................
~Wonder why Mercury did not hire or consult him.........................................................................
~Is the word sweep from a plumbing term like a toilet waste line for a smooth non sharp bend...........
~Heck, a guy that goes to work with a Rolex must be successful....................................................

PS; had time this morning just had toooo...............................

[Chaz]

Mr. Tee,

It's all math, some much more complicated than others ..
Blown alky dragsters I built, used an 1.250" alum tube for a fuel line ..
When I met him he worked for Mike Thermos @ NOS, then Holley, now his own ..
It's slang, common thought is, kinked (also slang) adds approx. 12" line length over a swept fitting ..
If you wear a Rolex these days, sadly, you should probably carry a gun .. too big to wear on my wrist, but my cell phone has a clock ..
I'm glad you did, your a great source of information .. < (Ice tea)

Chaz = thinkin, when I ask the Merc. tech reps a question .. 99% of the time, they say … I'll have to back to you ..

[wetsetmarine]

So Chaz...Would you recommend that I remove VST on my stock 300X? Just bought it and want it to live.

[Chaz]

If it's lasted this long with it .. why change ?
I would make sure it would stand a good chance to remain living by ...
Running fresh 93 fuel
A good grade oil
Fresh kit in the pulse pump
Not an inch of 5/16 hose anywhere in line
The thermostat's are in working order
The spring in the regulator hasn't "sacked out" and has less than 40 PSI of fuel pressure. I'd put an adjustable kit in it , so you can bump it back up to where it belongs. ( Busters in NY has/had some NOS regulators, there not cheap )
If you insist on putting a huge prop on it or your boat weigh's a lot, I'd avoid lugging the motor into detonation .. ( do as I say, not as I do, my mom would say .. )
To take the VST off, you would need a dedicated well thought out fuel system, that would entail every single piece or part that the fuel touches, except for the injectors.
Then at that point, the choice is yours …

[tux974]

Wise guy, like the smiley!!!!.........
You never listen to mom anyway or you would have been a scientist.......

Hope you and Deb are doing well with these crazy and concerning times!

[Chaz]

Mr. Tee,
I was in the back seat of my parents car one day and the song "Mama said there would be days like this" came on the radio … I sat up and said, Yo ma, why didn't you warn me ? She stared a hole thru me in the rear view mirror with 30 years of pent-up frustration .. Oh I did, you were just way to *&^$%&&% hard headed to listen … Yes ma'am, your right, bad attempt at a joke .. as I slumped back in the seat … with as much humility as I could muster …

You guys be safe as well. We have only had a few cases in town here .. I watch TV and start to worry about my friends in the N.E. and have to shut it off ..

I reckon it's a good thing I don't live in a highly effected area. I wake up, rub my eyes, pick my nose and make a bacon, egg an cheese sammich .. break all the rules before I even start the day ..

[wetsetmarine]

Thanks Chaz Tux!! Doing all the suggestions!!

[Chaz]