1978 Evinrude 4hp fuel question

[curtis4769]

I will give you guys the whole story so you can best help me diagnose the problem.

I run rafts from Moab, Utah through cataract canyon and out of Lake Powell. A distance of over 100 miles.

I just got back from a trip and brought two motors that I got working (thank you for all the replies to my previous threads)

One motor is a 1971 Johnson. I rebuilt the carb and replaced the impeller on it and it ran like a dream for many days straight on the trip.

The second motor is a 1978 Evinrude 4hp. This motor gave me a few problems on the trip and I need some advice. The first day we fired up this motor it ran fine for 6 hours with no issues at all. The second day the motor ran for 2 hours and just quit randomly. When we pumped the primer bulb from the gas tank it would start again but die after a few minutes. Then I would press the primer bulb and it would not get hard. When we switched to the 71 johnson the bulb got hard and that motor ran flawlessly, so I have eliminated the tank and primer bulb as the problem. Does this sound like the fuel pump or a carb issue?

 

[Rick.]

Re: 1978 Evinrude 4hp fuel question

If it ran flawlessly on the Johnson Bulb but not on it's original I would suggest you change out the original hose/bulb before you look for fuel pump/carb. issues. I hope I'm understanding what you've done. The thing that throws me is you say you've "eliminated the tank and primer bulb as the problem" where as the way I'm reading it you have proven it is the problem. Common thought is you should run a 25/1 mix in that 71 Johnson, not sure about the 78. Best of Luck. Rick.

 

[curtis4769]

Re: 1978 Evinrude 4hp fuel question

Thanks rick, sorry if I wasn't clear. I was using the same gas tank/hose/primer bulb for both motors. The bulb gets hard and everything works with the 71 johnson, but the bulb doesn't get hard when attached to the 78 evinrude.

 

[hidef]

Re: 1978 Evinrude 4hp fuel question

I would say it is time to rebuild the fuel pump. The 1978 4 horse can safely use 50:1 but running 24:1 will not hurt it if are swapping tanks around because you don't want the 71 running 50:1..

 

[curtis4769]

Re: 1978 Evinrude 4hp fuel question

hidef, I was using 24:1 for them both based on your advise a few weeks ago. I suspected the fuel pump but wasn't sure because it had ran fine for 6 hours the previous day. Do I need to get an entire new few pump ($) or is there a certain part I could replace that is causing the bulb not to get hard?

 

[Rick.]

Re: 1978 Evinrude 4hp fuel question

No disrespect meant here for sure as hidef may well be right. I'm just thinking if it ran for six hours the pump may be just fine. When the bulb doesn't get hard (and I know the bulb is good) I normally suspect the float needle is not seating correctly unless I can see obvious fuel leakage elsewhere. Rick.

 

[hidef]

Re: 1978 Evinrude 4hp fuel question

You can order a new pump

http://www.marineengine.com/parts/j...4836E&manufacturer=Evinrude&section=Fuel+Pump

Or rebuild yours

http://www.marineengine.com/newparts/part_search.php?part_num=393088&submit2=Go

The pump wore out simple as that. When you pumped the primer bulb you said the engine would run for a little bit then die that is the symptom of a bad fuel pump.

 

[curtis4769]

Re: 1978 Evinrude 4hp fuel question

Rick, that's what kinda confused me as well. I think I'll just throw a carb kit at it and if that doesn't work I'll tackle the fuel pump. It probably still has a cork float in it that I should replace anyway.

 

[curtis4769]

Re: 1978 Evinrude 4hp fuel question

hidef, I need these things to be reliable so I guess I may as well pony up the cash and get the fuel pump as well.

 

[Rick.]

Re: 1978 Evinrude 4hp fuel question

The kit for my 71-4hp-Evinrude came with a brand new cork float. I was surprised they hadn't gone to a composite material. What good is a float if it only lasts 40 years? LOL. Rick.

 

[hidef]

Re: 1978 Evinrude 4hp fuel question

If you are ordering parts you might as well order the rebuild kit for the old pump. You can rebuild it and keep it as a spare. If your fuel lines are old replace those as well as Ethanol in the gasoline raises hell with the old fuel components until they are rebuilt with new parts.

http://www.leeroysramblings.com/Rebuilding_fuelpump.htm

 

[curtis4769]

Re: 1978 Evinrude 4hp fuel question

hidef, do you happen to know the size of fuel lines I would need to order for the 71 and 78. The lines from the tank are new but everything after that are old. Thanks man your knowledge makes working on the old 4hp's a lot easier

 

[Rick.]

Re: 1978 Evinrude 4hp fuel question

If you are ordering parts you might as well order the rebuild kit for the old pump. You can rebuild it and keep it as a spare. If your fuel lines are old replace those as well as Ethanol in the gasoline raises hell with the old fuel components until they are rebuilt with new parts.

http://www.leeroysramblings.com/Rebuilding_fuelpump.htm

Now that's the best advice you got today. When you depend on a motor, and it sounds like you do, it's well worth spending some extra cash to eliminate even potential problems. I don't recall the gas line sizes but if you take samples with you to an auto parts store they will more than likely have what you require. Rick.

 

[curtis4769]

Re: 1978 Evinrude 4hp fuel question

Well, I went out to work on the 78 evinrude today, hooked up the gas tank and the primer bulb got hard. Started it up and ran it for like 20 minutes in the barrel. Maybe the carb float was just stuck and that was causing the bulb to not get hard?