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Old 02-05-2011, 06:22   #1
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What Size Fuel Hose ?

I am replacing all the fuel hoses as part of my refit. After 25 years they have gotten pretty hard and one has already cracked on the end.

The old lines look really large to me, 5/8" ID from the dual tanks to the selector valve but only 3/8' from the selector to the Racor and fuel return line. Engine is a Westerbeke 58. Hoses, supply and return from each tank to the selector are about 10', about 3' to the Racor and return line from the engine about 4'.

I think the 5/8" is overkill for this size engine. Wouldn't 3/8" hose be adequate, even for the distances between tanks and engine?

I do plan to relocate the selector in the process which would put it closer to the tanks but then give about 10' to the Racors? Any reason not to keep that part of the run 3/8' even if it is further away?

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Old 02-05-2011, 07:23   #2
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Re: What size fuel hose

Diesel Fill pipe systems must be minimum 1-1/4" ID, requiring min. 1-1/2" ID Hose.
Diesel Vent pipes must be minimum 7/16".

Engine Fuel Supply pipes will depend upon specific engine. Consult manufacturer.

Westerbeke 58 Manuals:

Partshttp://www.dublerfamily.com/Regina_o...Searchable.pdf

Owner’s ➥ http://www.dublerfamily.com/Regina_o...nersmanual.pdf

Technical ➥ http://www.westerbeke.com/OnlineManu...ech_Manual.pdf
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Old 02-05-2011, 08:32   #3
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Re: What size fuel hose

Of course Gord is correct to suggest going with the manufacturers specs.
If that is not clear or available, I would think that 3/8" would be a safe assumption.
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Old 02-05-2011, 08:51   #4
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Re: What size fuel hose

Just my $.02. I find that 5/8" seems to be the most common size for various mfgr fuel fittings (like tank vents, check valves, etc). Not familiar with your installation, going with something smaller risks more size adapters.

For fuel I would guess it is better to go bigger than smaller?
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Old 02-05-2011, 09:40   #5
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Re: What size fuel hose

Quote:
Originally Posted by westsail42 View Post
Just my $.02. I find that 5/8" seems to be the most common size for various mfgr fuel fittings (like tank vents, check valves, etc). Not familiar with your installation, going with something smaller risks more size adapters.

For fuel I would guess it is better to go bigger than smaller?
I looked at the fittings and the tanks and selector valve all have adapters that are 3/8" NPT male threads with hose barb on the end. Should be a simple task to replace all the NPT adpaters with another with a smaller hose barb.

I agree that generally bigger is better but in this case running a smaller, more flexible hose will simplify the process a LOT, plus save a couple of bucks for the smaller hose.
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Old 02-05-2011, 09:48   #6
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Re: What size fuel hose

Quote:
Originally Posted by GordMay View Post
Diesel Fill pipe systems must be minimum 1-1/4" ID, requiring min. 1-1/2" ID Hose.
Diesel Vent pipes must be minimum 7/16".

Engine Fuel Supply pipes will depend upon specific engine. Consult manufacturer.

Westerbeke 58 Manuals:

Partshttp://www.dublerfamily.com/Regina_o...Searchable.pdf

Owner’s ➥ http://www.dublerfamily.com/Regina_o...nersmanual.pdf

Technical ➥ http://www.westerbeke.com/OnlineManu...ech_Manual.pdf

Thanks Gord,

Haven't even looked at the fill and vent yet. Started at the bottom and working my way up, not to mention that the fill and vent hoses are harder to reach.

Read the manuals, what a concept. Even though I might feel my manhood threatened I might give that a go.

Assume that for similar horsepower which typically means similar fuel use that requirements for various engine makers would be the same. And, since there are a number of other variables like distance of the hose run which will incur some cumulative resistance, lift if any from tank to engine, number of sharp turns or 90 degree elbows in the line, that the engine manual might not cover the subject in detail. Guess I will have to break down and actually look.

Meanwhile if there is marine mechanics rule of thumb I'm interested.
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Old 02-05-2011, 09:50   #7
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Re: What size fuel hose

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Originally Posted by James S View Post
Of course Gord is correct to suggest going with the manufacturers specs.
If that is not clear or available, I would think that 3/8" would be a safe assumption.
Since the system is 5/8" only from the tank to the valve and 3/8" from the valve to the Racor to the engine and back I can't see why it couldn't be 3/8" all the way. But I have gotten myself in trouble making assumptions in the past so thought I would ask for a second (third, fourth, etc) opinion.

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Old 02-05-2011, 09:56   #8
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Re: What size fuel hose

Mine is 85 hp Naturaly asperated...3/8 all the way..top of tanks are about the same height as the top of the engine...hose length to filters 8 to 10ft....filters to engine I'd say another 4 or 5ft.
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Old 02-05-2011, 23:20   #9
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Re: What size fuel hose

I have a 40 hp Yanny and it has 5/16" (8 mm) ID hose throughout the motor from the factory.
As for yours, if its factory, I would suggest going to the same size as the inlet on your fuel pump. Anything more then that is a waste, especially at todays prices, unless it is a looong run. Then one size up should do.
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Old 03-05-2011, 06:35   #10
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Re: What size fuel hose

Quote:
Originally Posted by delmarrey View Post
I have a 40 hp Yanny and it has 5/16" (8 mm) ID hose throughout the motor from the factory.
As for yours, if its factory, I would suggest going to the same size as the inlet on your fuel pump. Anything more then that is a waste, especially at todays prices, unless it is a looong run. Then one size up should do.
That is the logic I was using. Fuel pump and fuel return lines on the engine are all 3/8" so seemed to make sense that 3/8" should work in the rest of the system. Just ordered a roll of 3/8" A1 hose and will replace the hose barbs on the tanks and selector valve to fit.

Thanks all,

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Old 03-05-2011, 07:21   #11
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Re: What size fuel hose?

5/8" fuel line has 3 times the area of 3/8", .31 against .11 sq.ins. 3 times the atmosphere to evacuate when re-priming the fuel system. Thats lots of hand-pumps at the filter. Don't try it on the starter motor, it'll probably burn out.
I pressurize mine with a short vent hose extender, and an inflated childs party balloon. Pushes the fuel right up to the Racor.
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Old 03-05-2011, 08:21   #12
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Re: What size fuel hose?

My Perkins 4.108 manual specs 3/8 or 1/4 inch feeds to the primary lift pump. Was set up with 3/8 to the Racor and 1/4" to the primary lift pump runs fine. A search of your manual if you have one should give you factory specs.
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Old 03-05-2011, 08:24   #13
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Re: What size fuel hose?

Quote:
Originally Posted by Blue Stocking View Post
5/8" fuel line has 3 times the area of 3/8", .31 against .11 sq.ins. 3 times the atmosphere to evacuate when re-priming the fuel system. Thats lots of hand-pumps at the filter. Don't try it on the starter motor, it'll probably burn out.
I pressurize mine with a short vent hose extender, and an inflated childs party balloon. Pushes the fuel right up to the Racor.
I like that idea. Was looking at other alternatives to pump/prime/bleed the fuel system. A couple of guys have installed an outboard motor style squeeze bulbs in the fuel line from the tank for this purpose. Works for them but I don't really have a good, accessible location to install one in my system. Pressurinzing the vent line would be easy and not require additional breaks and fittings in the fuel line, always a good thing.

Not sure if a balloon would provide enough pressure for my boat. Is your fuel tank above or below the Racor? By how much?

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Old 03-05-2011, 08:30   #14
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Re: What size fuel hose?

Primer bulbs inline for diesel fuel powered engines can end up causing more trouble than they are worth. The priming pump on the primary lift pump should be all that is required. If you have been having trouble priming your motor consider an electronic fuel pump.
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Old 03-05-2011, 08:45   #15
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Re: What size fuel hose?

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Originally Posted by cburger View Post
Primer bulbs inline for diesel fuel powered engines can end up causing more trouble than they are worth. The priming pump on the primary lift pump should be all that is required. If you have been having trouble priming your motor consider an electronic fuel pump.
Have not had a problem priming and bleeding the system once I had fuel to the Racor. The problem I had was getting fuel down a 10' X 5/8" fuel hose from the tank to the Racor.

When I first bought the boat had a lot of problems with the fuel system including a very old Racor with leaking fittings and no availability of new parts to fix, old fuel lines that were cracked and sucking air at several fittings and more. So spent a lot of time filling, bleeding, draining, etc and the little priming pumps on the engine just were not up to sucking fuel up from the tank to the filter. Estimated about 3/4 gallon of diesel to fill the line from the tank to the filter. That's a lot of pumping.

Once I have the system overhauled I hope to never have to do that part again. Will have new fuel hoses and a shutoff at the Racor so I won't loose prime back to the tank when I change filters but will still want to pressurize the line from the tank to the filter to fill the new filter and bleed out the last few air bubbles, something you can't do with the lift pump on the engine since it is sucking from the filter.

Some have reported great success with the bulbs but I'm reluctant. Hence the interest in the air pressure idea.
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