Need help with a run-away 1983 70hp

[trimmers]

Motor ran fine last week on the water for hours, did a fresh water rinse when done playing with no issues. Now today while on the muffs, it is running away! Here is what I did so far to diagnose issue: Pressed electronic choke in while running and it started to caugh and wanna die. I ensured the butterfly linkage was not bound up and the butterflies were closed. I manually pulled the throttle linkage back some with very little difference. All 3 cylinders appear to be same temp by touch. Ensured good fuel. Manually engaged choke lever and killed the motor. I am lost. I did hear a weird sucking sound out of the bottom cylinders carb as the motor was laboring to run at one starting attempt, then the sound went away, and the motor ran up again. Each time, it hits about 1500 rpm's and I kill it. But it seems like it will run up alot more. Maybe a reed valve? Help Please! Thank You

 

[trimmers]

Re: Need help with a run-away 1983 70hp

Update! Inbetween Lightning storms, I managed to pull out a compression check. 100psi on all cylinders. Also, I removed the lower carb and all 4 reed valves appear to be fine. Closed up the carb and started the motor. All ran good at normal idle rpm's for about 20 seconds and then without seeing any movement in the linkages, the motor ran up to about 2500 rpm very quickly before i could kill it! I am at a total loss?

 

[clemsonfor]

Re: Need help with a run-away 1983 70hp

Check the float levels on the carbs, make sure its not flooding. You can squeeze the primer bulb and see if fuel flows out of carb throats. My point is that this excess fuel will puddle in the bottom of the air box and if you have a carb sucking air your getting more air than you should creating vacume to suck that excess fuel into the recirculation hose and into the motor and make it fuel up beyond idle. Not a gaureentee just a thought?

 

[trimmers]

Re: Need help with a run-away 1983 70hp

That definetely is a good point. I will try that tomorrow morning. Will post results, thank you

 

[jtexas]

Re: Need help with a run-away 1983 70hp

before starting the motor again, inspect your spark plugs, look for evidence of pre-ignition and/or detonation

http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

 

[ScottinAZ]

Re: Need help with a run-away 1983 70hp

does your engine have choke plates on the carbs, or does it have an enrichener solenoid in place of the choke. If it has the enrichener (my 82 115 has one) and it is stuck OPEN, then it will feed fuel past the carbs. usually the enrichener is a round black thingy about an inch and a half in diameter and it will have a lever on the top of it with fuel lines in and out. I make note of this, because you did not mention if you had the issue before you started with the choke.

 

[trimmers]

Re: Need help with a run-away 1983 70hp

it has an electric solenoid for the choke. It ran away prior to playing with the choke. The plugs seemed fine and there was no evidence of pre ignition on the plugs or pistons. Will be trying the fuel bulb check in a few hours and will post results. Thank you for the advice, i am really puzzled

 

[Boss Hawg]

Re: Need help with a run-away 1983 70hp

Motor ran fine last week on the water for hours, did a fresh water rinse when done playing with no issues. Now today while on the muffs, it is running away! Here is what I did so far to diagnose issue: Pressed electronic choke in while running and it started to caugh and wanna die. I ensured the butterfly linkage was not bound up and the butterflies were closed. I manually pulled the throttle linkage back some with very little difference. All 3 cylinders appear to be same temp by touch. Ensured good fuel. Manually engaged choke lever and killed the motor. I am lost. I did hear a weird sucking sound out of the bottom cylinders carb as the motor was laboring to run at one starting attempt, then the sound went away, and the motor ran up again. Each time, it hits about 1500 rpm's and I kill it. But it seems like it will run up alot more. Maybe a reed valve? Help Please! Thank You

Maybe a reed valve?

Had the same problem with a '87 70hp & the "mechanic" said "Maybe a reed valve" -- Took it home, went to basics including a lync 'n sync -
Problem solved

 

[trimmers]

Re: Need help with a run-away 1983 70hp

On second thought, the air box (silencer) is removed so fuel puddling theory can't be it either. I guess a link and sync is in order. Will have to try that, however, like I said earlier, the butterflies are all closed. I can however, retard the timing manually while it is running and slow the rpm's down, but I think that is normal. Good Lord, I love I/O motors, they are so much easier than 2 strokes!!!

 

[jonesg]

Re: Need help with a run-away 1983 70hp

Ditto link and sync.

Running with no load its easy to experience a runaway.
Make certain the ignition timing is correct, if its advanced it will run too fast.

Then look for air leaks around carbs, air leak is the same as advancing ignition.

 

[trimmers]

Re: Need help with a run-away 1983 70hp

I was thinking about spraying wd-40 behind the carbs and see if I get any changes in motor rpm's. Is that a good theory?

 

[royal0014]

Re: Need help with a run-away 1983 70hp

before starting the motor again, inspect your spark plugs, look for evidence of pre-ignition and/or detonation

http://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

Ok, so not meaning to hijack a thread, but I think my Q applies here:

The above link provides useful information, for a four-stroke engine. How much would actually apply to a two-stroke? Seems to me that there would be a difference in the symptoms.....

OK, pre-ignition and /or detonation might show the same, but what about the other? Trying to learn something here.........

 

[trimmers]

Re: Need help with a run-away 1983 70hp

It would be pretty much all the same symptoms. Only instead of oil passing rings and fouling a plug and turning it nasty, it would be like running way too much mix oil and especially at low rpms (trolling). But all in all, the same. Rich, lean, predet etc

 

[trimmers]

Re: Need help with a run-away 1983 70hp

Well, I guess the butterflies were NOT all closed. The lower carb was cracked open just a tiny bit. Disconnected the link rod between the 3 carbs and problem solved! Made a slight adjustment on the set screw and good to go! Thank you all very much for your input! Anyone interested in my tilt and trim unit for a OMC V-6? 1987 yr model

 

[jtexas]

Re: Need help with a run-away 1983 70hp

Ok, so not meaning to hijack a thread, but I think my Q applies here:

The above link provides useful information, for a four-stroke engine. How much would actually apply to a two-stroke? Seems to me that there would be a difference in the symptoms.....

OK, pre-ignition and /or detonation might show the same, but what about the other? Trying to learn something here.........

add to what trimmers said, I expect to see a light coating of oil on the plugs especially after idling. A very light coating. not so much where they appear all black & gooey, just a little slick, if that makes sense.

I was thinking about spraying wd-40 behind the carbs and see if I get any changes in motor rpm's. Is that a good theory?

good theory, but....WD-40 used to use LPG as a propellent, now it's carbon dioxide...it's still listed as "flammable", but it's just not as combustible as it once was. So you can't really rule out a manifold leak with WD-40 anymore.

Glad you got if fixed...LOL @ "Good Lord, I love I/O motors, they are so much easier than 2 strokes!!!" ... how much easier than "sync the throttle valves, problem solved". Don't forget the number 1 advantage of the outboard: everyone can see how big it is!

 

[trimmers]

Re: Need help with a run-away 1983 70hp

I guess i like inboards cause of my car racing background. I know them so well, and they have ONE carb! LOL, 3 carbs on a motor that weighs 200lbs???!!! lol,