Fuel Line Question

[ThePatriot]

Hi all

I have a 2005 Honda BF150 on my SR.

The fuel hoses from the tanks to separator filters are all 3/8.  From the separator to the motor (bulb hose) the line is 5/16?

The bulb hose is looking tired and I want to change it out.  Honda parts are calling for a hose labeled 7.3x2000.  I'm assuming that's mm.  Which would make it slightly smaller than 5/16. 

I always thought that motors over 100hp should have 3/8 fuel hoses?

Any thoughts?


Sent from my iPhone using Tapatalk

[ohmytodd]

I have the same main as well as a kicker that take 5/16. Everything works just fine, and yes, that factory Honda line is a tight fit on a 5/16 barb, but it works. Sportcraft should have those fuel line assemblies in stock, but they're pricey!

[ThePatriot]

Yeah mine has worked fine too but I've been reading that 5/16 on that size motor could make it run lean at higher RPMs.


Sent from my iPhone using Tapatalk

[ohmytodd]

Yeah mine has worked fine too but I've been reading that 5/16 on that size motor could make it run lean at higher RPMs.


Sent from my iPhone using Tapatalk

I don't think you'd have an issue, it's factory spec. Larger probably won't hurt anything, but you'd need an adapter to size down to the motor connection or find an aftermarket connector.

I had Sportcraft replace all of my lines last Fall to factory spec and they used the smaller diameter.

[Fisherdv]

With the Honda motors being so fuel efficient, I think you will be fine with the factory rated diameter. 5/16 under pressure should be more than enough fuel.

[davidsea]

   Back in the middle ages, when I used to race boats, we had similar concerns.  In the days of carburetted 2-stroke motors, with wimpy diapragm fuel pumps run on crankcase pressure pulses, going lean on top end was a very expensive no-no. Engine RPM would increase momentarily, followed by loud noises and then complete silence. The old rule-of-thumb was that fuel flow was 1 gallon per hour for every 10 horsepower being developed - a motor putting out 100 horsepower would burn 10 GPH.  That old rule is pretty much still true, although newer 4-stroke, fuel-injected, electric fuel pump, computer-controlled motors do a little better than that, and are a lot less likely to be affected by restricted fuel flow.   Some of the race guys set up a very simple test - they hung lengths of fuel line vertically, stuck funnels in the top, and measured how long it took for gravity to push a measured amount of fuel through.  Without a pump (actually, without vacuum), it was thought that 5/16" was good to about 125-150 HP, and 3/8" from there up, except for the 300+ HP race motors, which used 1/2" line and regulated electric pumps.  For Arima-size modern motors, I'd be comfortable with 5/16" for everything except for 200-250 V6's.

[ThePatriot]

Thank you.  I think I'll stick with the recommended 5/16 replacement. 


Sent from my iPhone using Tapatalk

[mariner]

Thank you.  I think I'll stick with the recommended 5/16 replacement. 


Sent from my iPhone using Tapatalk

If the fuel hose that comes out from under the cowling of your BF150 is 5/16 and the manual states 5/16 is appropriate, stick with it.   Wouldn't hurt to contact a Honda dealer and ask what they recommend.  I don't know about Honda but current generation midsized to large Mercury OB have on their manual and from Merc technicians to NOT put a primer bulb or any additional in-line fuel filters(apart from the dedicated water/fuel separating filter) or anything that can restrict fuel flow to the engine.