87 johnson 70 hp, still surging w/video

[cold_gin]

Ok second post on this motor. When i got this boat it was running really bad and surging/boggin down at all speeds above idle. All cyls above 100 compression and all within a few psi of each other. List of new parts;

spark plugs, spark plug wires, power pack, one coil replaced, rectifer replaced. carbs cleaned out. fuel bulb replaced.

Seems like every time I worked on it, it would run better. Now its runs really well on the muffs idles good and very responsive when u snap the throttle, but seems to idle a little rough on the water, at up to 3/4 throttle it runs pretty good. Once you get past half idle u can see/feel the surge and at full throttle will run briefly and bog down.

This boat defintely had an ignition problem with a spark tester attached u could see the spark was intermittant and now im kinda stumped. Im thinking maybe the carbs still, but when u squeeze the primer bulb at surge it doesnt do anything for it.

heres the video i took a couple hours ago

70hp johnson - YouTube

 

[Cap'n Chaos]

Re: 87 johnson 70 hp, still surging w/video

It almost looks like it's starving for fuel....have you checked the fuel pump? Gas tank vented?

 

[fishfeatures]

Re: 87 johnson 70 hp, still surging w/video

It almost looks like it's starving for fuel....have you checked the fuel pump? Gas tank vented?

he does say that squeezing the bulb doesn't solve the issue, so this would bypass the fuel pump .....

Have you checked to see if the reed valves are ok? I had a chipped one once that caused similar symptoms as you're having.....

 

[Bosunsmate]

Re: 87 johnson 70 hp, still surging w/video

With engine off prime your bulb firm, check it holds for a while.
Sometimes the floats will close the pump off at low rpms but as rpms incrrease the extra pressure is too much and will flood causing symptoms like you have

 

[cold_gin]

Re: 87 johnson 70 hp, still surging w/video

yeah bulb holds firm, not sure what you mean about the floats closing the pump off

 

[Bosunsmate]

Re: 87 johnson 70 hp, still surging w/video

closing pump flow off is what i meant.
Have you tried hitting the choke when it starts spluttering?

 

[cold_gin]

Re: 87 johnson 70 hp, still surging w/video

yep hit the choke as well, doesnt make a difference

 

[Bosunsmate]

Re: 87 johnson 70 hp, still surging w/video

How do the plugs look?

 

[cold_gin]

Re: 87 johnson 70 hp, still surging w/video

took them out and they all were wet and looked the same

 

[Bosunsmate]

Re: 87 johnson 70 hp, still surging w/video

Is the timer base advancing properly with throttle to the spark advance throttle stop

 

[LongLine]

Re: 87 johnson 70 hp, still surging w/video

Make absolutely sure that those "lousy" 4 pin connectors are in good shape, properly seated and your getting good contact.

Tom B.
(LongLine)

 

[cold_gin]

Re: 87 johnson 70 hp, still surging w/video

The base is moving all the way to the rubber stop.

 

[cold_gin]

Re: 87 johnson 70 hp, still surging w/video

So im thinking either timing or too much fuel. If the choke solenoid goes bad, can the carb suck gas thru it? Im thinking about unhooking from the fuel and see if that helps.