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87 Evinrude 70 Idle Problem

J

jgarner56

New member
Hello All,
New to posting here (1st) but have been researching quite awhile on this forum. Cant seem to find my problem in previous post.
87 Evinrude 70 TLCUR.
Compression Check 105, 105 and 105.
Spark is strong on all three.
Fuel delivery is now a concern.

Problem started after first outing of the season, just a quick run on the river. Thermostat hung and engine overheated but caught it just as it happened.
Decided to do minor tune up as well after the water pump which included flushing the carbs. Ended up pulling them and found no varnish, trash or build up in the bowl.Cleaned with B12 carb cleaner and compressed air including the idle path but did not have welch plugs so did not go into the full idle circuit but soaked them good. Even used the small electrical strands in the orifices.
List of parts on repairs
waterpump assy, shift hsg seals, Champion plugs, new thermostat and sealing grommet,gasket, carb bowl gaskets,nozzle gaskets.

All back together and now the idle will fluctuate every 15-20 seconds. Cannot pinpoint the problem to float or idle circuit.
I use non ethanol fuel. Eng still has the vro system and appears to work as designed.

I have a video that I was going to link or post.
Any help would be appreciated with comments, concerns or help in linking my video.
Thanks in advance.
 
You say the idle fluctuates every 15-20 seconds. If that means that the engine's rpms increase, then decrease all by itself.... that is due to the throttle linkage between the carburetors being incorrect. This would normally leave one butterfly completely shut as it should be at idle BUT have the butterfly on another carburetor slightly open.

Top check this, simply pop the throttle linkage off the top and bottom carburetor when it's idling.
 
Thanks Joe I will check this and report back.
I havent timed it by a watch but it seems to change in about that time.
It seems to idle up or seems that way. I did the normal checks on reassembly, but didnt move any linkage adjustments on the carbs.
It just seems like a fuel delivery on maybe one carb.
Ill check the butterflys as instructed.
 
Ok I popped the linkage loose on top and bottom. Same. Plates look closed. Popped the linkage all the way. No change still has the same idle.
 
jgarner56 said:
Ok I popped the linkage loose on top and bottom. Same. Plates look closed. Popped the linkage all the way. No change still has the same idle.
Click to expand...

Bummer, worth a try anyhow. Is that up and down surge a gradual rpm change (Fuel) or a quick instantaneous change (ignition)?
 
It appears to be gradual on the up and quick to low side. I'm loading a video to you tube and will link it in. I bought welch plugs yesterday just incase I go back into the carbs for the idle circuit.
I've owned this boat/eng 3 seasons, ran fine two seasons. Never had an idle issue.
Thinking it was bad fuel I swithed out the feed line to fresh gas and it didnt change anything. Still has an old smell on fuel burn. The carbs were clean but did find a rust line on bottom carb float but no water. I may do a premix test and see if that changes anything. Not sure what I have to unplug-plug off on the vro to do that. Will have a video up that will hopefully give a better idea of whats happening.
Thanks again Joe
 
Update since posting the video. (Has to be fuel delivery problem)
Checked the spark again- Crisp 7/16 spark on all three coils.
Son stopped by on Tuesday so during our chat the engine problem came up- test fired it so he could take a look. During that test idle the top cylinder went dead. Checked the spark -good. Then removed the flame arrester to check the fuel on the top cylinder carb- zero fuel. Squeezed the primer bulb-still no fuel on top carb. Tapped the carb to see if float would drop open-nope. Pulled carb and bowl. The float needle valve was literally stuck to the seat. Checked the needle valve- the sealing area was deteriorated.
Ordered 3 needle valve and seats and floats. Pulled the welch plug on top carb, idle circuit is clear- no varnish,trash or residue.
As soon as I get the parts then we will clean and assemble the carbs with the new parts. Test run again. If I still have a problem, its going to the dealer technician.
 
A suggestion for all...... When going to the trouble to remove and clean carburetors, rebuild them with a complete carburetor kit so as to restore them to their original new condition.
 
jgarner56 said:
I should have have got the kits. Funny how whats not in budget suddenly gets put in the budget.
Click to expand...

Understood. I too have went the shortcut route at times due to a temporary financial shortage, but usually found myself doing duplicate work. Just too tempting to avoid when the $$$ is somewhat lacking.
 
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