70 hp Evinrude problem

[Florida Boater]

I have a 1988 70hp Evinrude. Problem is runs good anything above about 1/3 throttle. At idle & slow speed acts like 1 or 2 cyls cutting in and out. What I have done so far. Cleaned and installed kits in carbs. New plugs, twice. New head gasket. Removed reed plate, reeds look good. Tested the coils, tested good. With a spark tester spark looks good. Compression 100 lbs on all cyls. Running it on a hose the upper cyl is the one running strong. You can block off either lower carb, makes little difference. Squirting gas into either lower carb makes no difference. If you block the upper carb motor dies instantly. Switched upper coil and wire with center coil. No difference. I have given the charge coil and sensor coil a resistance test, they test good. Don't have the equipment for output tests. Years ago I was an outboard mechanic so I know a little about repairing outboards but apparently not enough. Could a power pack act this way? Don't know what to try next. Any suggestion would be appreciated. Not Fishin.

 

[tashasdaddy]

Re: 70 hp Evinrude problem

pull each plug wire individually and note any difference the the running of the motor. if there is no difference, then that cylinder is not runnin. then you need to put the spark tester on it, and see if it is firing. if firing then it is not getting fuel.

you may also need to do a link n sinc. aligns spark and carb so the work together. also timing.

 

[HighTrim]

Re: 70 hp Evinrude problem

Sounds fuel delivery related. Does it only do this when warm or all the time? Pumping the fuel primer bulb pick it up at all? I assume you removed the slow speed jet from the carb when rebuilding and giving it a thorough cleaning, not just soaking it? All fuel lines tight, no leaks?

 

[ICEMAN]

Re: 70 hp Evinrude problem

there is a condition where the power pack can double fire on the cylinders. this is checked using a timing light. you may have to remove the spark plugs and index the flywheel so you have a mark where #'s 2 and 3 would fire at TDC. run the motor and light up the flywheel and see if it shows two numbers firing at the same time. try it on all cylinders, if shows 2 firing, the power pack is N/G.

 

[RJDAWSON]

Re: 70 hp Evinrude problem

I had a similer problem with a 79 70Hp, the stater was bad. Check the Stater if it is gummy to the touch or shows a tar like material on it, it may have overheated. I think replacement is in order.