Stumped -- 1981 Evinrude 70hp stalling during acceleration

dmadey · #1 June 20th, 2006, 02:02 PM

Please help if you can! I've been struggling with this stalling issue on my E70ELCIH since last season and I'm stumped. I've spent weeks reading articles on this forum and have tried the suggestions I've found ... but without success so far.

Symptoms/behavior of the engine is:

- Engine idles well when cold and while warming up(both in and out of gear). Once the engine is hot (e.g. after running at high speed for a while), it will stall while in gear going at low speeds.

- Engine runs great at high speed (once I coax it there)

- Engine stalls during acceleration 90% of time. During the stall, choking the carb doesnt help and pumping the fuel bulb does not help.

- In the event the engine doesnt stall, the engine moves slowly towards higher rpms like it's trying to 'catch up" to itself. The rpms steadily rise although the throttle is stationary.

I've done the following work/troubleshooting in an attempt to fix it:

- Rebuilt Carbs, verified proper float positioning, replaced all parts including core plugs. Verified complete cleanliness of carbs.

- Rebuilt Fuel Pump.

- Replaced sparkplugs.

- Verified good spark in all 3 cylinders both idling and in gear.

- Verified good compression (100-110 psi while trying to key-start with no plugs)

- Performed partial link and sync -- I synchronized the throttle and choke linkages. I verified the timing advance at idle was 2 degrees but I havent done the maximum spark advance measurement yet.

- Verified that timing plate is moving smoothly during throttle advance. The timing plate starts moving when the throttle is at about the "11:00 position" and stops moving when it's about at "10:00 position".

- Verified proper tension in throttle cables

- I'm using fresh gas with 50:1 ratio gas to evinrude/johnson 2-cycle oil

What should I try next!???!? Thanks in advance for any help !!!

rickdb1boat · #2 June 20th, 2006, 02:31 PM

I would try this:

web page

OBJ · #3 June 20th, 2006, 03:35 PM

If after resetting the WOT timing doesn't work, check and make sure the choke plates are coming fully open. Doesn't sound like fuel starvation....but to much fuel. Are you sure the float settings are correct and the floats are free to move up and down?

You might pull the pulse line off the fuel pump and squeeze the primer bulb. Watch for any fuel that may come out of the pulse line connection nipple on the fuel pump. If you have fuel there while squeezing the primer, it means the diaphram is shot and allowing fuel to get into the engine through the fuel pumps pulse line.

Have you checked all your fuel lines to make sure all are in good condition...ie...not hard...and are making good connections?

dmadey · #4 June 20th, 2006, 05:31 PM

Thanks, Rick. I'll try the WOT Timing setting procedure this wknd. My boat is moored down at the creek and I wont be able to get to it before then.

Thanks to you also, OBJ. The choke plates are fully open during the stalling. I verified the float settings and movement -- this is all per the manual. I just rebuilt the fuel pump so I'm pretty confident the diaphram is good. The fuel lines are pretty old and could stand to be replaced but I'm not sure how bad lines could contribute to too much fuel. However, I should probably replace these for good measure.

For what it's worth, I forgot to mention in my earlier post that I also put a new powerpack on the engine last month.

OBJ · #5 June 20th, 2006, 06:25 PM

Lose fuel lines can suck air hounddog. Won't cause too much fuel but can make the engine run ragged. Sorry I didn't clarify that.....

billybones · #6 June 21st, 2006, 12:24 AM

Hi I am new and do not know a whole lot. But did have a buddy last year with a lot of the same problems. It ended up being that the vent to the tank was plugged. was a new boat and the mechs found it while looking at it. Was an outboard. Not sure what your engine is. I am a novice. so just sort of throwing that out..

dmadey · #7 June 21st, 2006, 09:36 AM

Thanks, OBJ. I'm going to replace the fuel lines on Friday, when I also do the WOT timing check. I'll let you know how it runs after that. I appreciate the feedback.

Billy bones, closed/clogged tank vents have stung me I've made sure mine are clear.

dmadey · #8 July 1st, 2006, 01:57 PM

Frank, that's really interesting. I'll have to try that.

Yesterday, I replaced every fuel line from tank to carbs and it didnt make any appreciable difference to performance. on the bright side...
- engine idles great and starts right up when engine is cold
- runs beautifully at higher RPMs. I took a 15 mile ride around the Severn River and Chesapeake Bay and the engine was very smooth.
however, persisting problrms are that...
- engine stalls during acceleration most of the time
- when engine is hot, it stalls at low speeds (e.g. going through no-wake zones after long time running at high rpm)
- when engine is hot, it has problems starting and seems to flood very easily (this flooding problem is new)

I still havent attempted the WOT measurement -- I cant access the link that Rickdb1boat posted above. I am planning to try it one night when I can get out around dusk with a friend and it's dark enough to be able to see the timing strobe on the wheel. Honestly, though, I cant see how the WOT setting would cause these issues.

So, I'm still stumped. Frank, I'm going to try your suggestion. I'll let you know what happens.

Thanks to anyone else that can help me get her running right!!