engine dies: 1989 70 H.P. Evinrude runs for five minutes, then quits

Have a 1989 70 H.P. Evinrude that runs for five minutes at times, then just quits, may run more or less than that then quits. Choke it a couple of time and it will re-start and run awhile, then quit. Can someone point me in the right direction as to where the problem may lie. I have changed gas lines and fuel tanks, but it didn't help. Filter maybe, fuel pump maybe? Help me please.

Thank you very much in advance for any help.

 

I was going to suggest checking your gas tank vent,but that has been changed-was all that changed due to being rusty?

Unless they were,the small cheap easy stuff (filters,plugs,etc) would have been my first choice for replacement if only for maintenance.

Does it cut out only at idle,or also when you are motoring along at higher revs?

 

Try elevating your fuel tank so it gravity feeds, that might rule out the fuel pump. It is reasonably easy to check whether the pump diaphragm is perforated, and replace if needed. Other than that, sticking needle valve in a carb would only knock out one cylinder ?

 

Engine quits

Yes, it quits at faster speeds

 

Sounds to me like a partially clogged fuel filter or fuel line, particularly if the vent has been ruled out.

 

The fuel filter will almost certainly be part of the problem, something you can easily correct. Because this is a 23 years old engine, I would also remove the carbs and thoroughly clean them. If you find sediment in the float bowls, also clean the fuel pump.

 

It's only logical to establish a reasonable base line when doing this sort of work. Screw the parts you don't know about and R&R the appropriate consumables, then preform a basic systems check and tune up. Now you have a base line you can trust, no guess work. The first thing of course is a manual for the engine.



$30 and you can preform all the basic maintenance and tuneup procedures with confidence.

As has been eluded to by others, you likely have a number of issues. To beat around the bush a bit; fuel line deterioration particularity from ethanol added fuels, carb varnishing possably partially block passageways, used up consumables (filters, plugs, etc.), possible fuel pump output and other fuel delivery issues, etc., etc., etc.

The book will nurse maid you through the basics and get you on a level playing field, so you can make reasonable assumptions about the engine's condition and not be stymied by compounded symptoms

 

I recall many moons ago taking the fuel filter off a Johnson outboard and seeing it packed with debris, thought, "aha, there's the problem". It wasn't, amazing how it was getting enough fuel, but the issue was elsewhere. Can't remember what though, which is no help at all to the OP !

 

The most difficult is diagnosis. Your engine cuts out after 15 minutes.

That alone speaks a thousand words, spark plugs dont do that, coils maybe but dont start up again. Fuel supply unable to keep up the flow will!!.

Simple trick pump the bulb as its about to stop --if it picks up then its fuel.

Also the bulb should pump up hard, not flood or collapse.

 

You could try a compression test.A friend of mine had a similar problem on a 60hp 3cylinder,it would run for a while then cut out.It turned out to be one of the pistons partially melted.We replaced the piston and rings and it ran like a dream.

 

If you have changed fuel lines then the pump is next. There is little one way valves that can get dirt or rust. The gaskets are small and need carefull handling, they not only keep to keep fuel from leaking but vacuum pulses from the crank case equally as important.

 

Floating debris in the fuel bowl, priming bulb, etc. can also cause this. Again, start with a level playing field so you don't chase ghosts.

 

Floating debris in the fuel bowl? well if it could get through the filter it must be pretty small and therefore able get through the main jet. But the main jet takes from the bottom of the bowl and floating debris would be harmless

If ts floating I dont understand how the submerged pick up pipe could get it.

 

In the float bowl there is only sediment when you take the carb apart, but in a running engine the vibration will cause it to float.

I resuscitated my small Mercury that only kept running with the choke pulled. The fuel filter was clogged with colorless, sticky stuff and the float bowl contained a slimy brownish residue. I'm inclined to blame the overly expensive, environment friendly 2-stroke oil because with simple mineral oil I've never had such problems.

 

I've seen bits of gasket, "O" rings, fuel line pieces, chunks of varnish all floating the bowl. CDK is right, as soon as you start the engine it's in suspension and you'd think it would just get swallowed, but most of the time it just dances around. I've seen floats held open, jets partially blocked, the works.

I'm betting the hoses he has aren't ethanol rated and are breaking down, which leaves little bits of fuel line running through the system, eventually plugging up the works. It's also a pain the butt to remove all of them.