88' 70HP Evinrude, high idle

[scott324]

Hello all,<br /><br />I just got done rebuilding the carbs. Although there wasn't much too it. I replaced the float, needle valve a couple O rings and gaskets. The carbs have fixed low and high jets. I remounted them too find that it is idling very high. It jumps up to about 2200 rpms and stays. I followed the instructions in my shop manual, but the high idle is covered. Anyone have any suggestions as to what this could be? Thanks<br /><br />Scott

 

[JB]

Re: 88' 70HP Evinrude, high idle

Could be a lot of things, Scott, but my guess is an incompletely centered throttle butterfly in one carb, which would throw the "link 'n' synch" off.<br /><br />Good luck.

 

[BillP]

Re: 88' 70HP Evinrude, high idle

I cleaned an omc 70 carbs a couple weeks ago and reused the washer looking gasket that fits inside the carb for the nozzle. The motor ran really high rpms at idle when put back together. I cured it by getting new gaskets. No other adjustments made and the idle came down to normal...700 rpms.<br /><br />If you're careful the "link and sync" don't change when taking the carbs off.

 

[OBJ]

Re: 88' 70HP Evinrude, high idle

Could be either/or Scott. If you didn't use new gaskets, one of the nozzel gaskets, that's the little round gasket on the inside, could have broke and is allowing extra fuel into the throat.<br /><br />Pull the carb cover and look down the throats. See if any of the throttle plates are open more than the others. Only takes a little bit of opening to increase rpm. <br /><br />If the plates look seated, start the engine and look at the nozzles in each carb. At that high rpm, you should be able to see the fuel being sucked from the nozzle into the carb throat. A good flash light helps.<br /><br />Keep us posted....thanks.

 

[BillP]

Re: 88' 70HP Evinrude, high idle

A timing light works good for checking nozzle spray too.

 

[scott324]

Re: 88' 70HP Evinrude, high idle

Thanks for all of the replies. Bare with me, but isn't the butterfly the plate inside the throat of the carb that restricts airflow and opens with increased throttle. If so I didn't touch them at all and they all look to be in the same position. <br /><br /><br />I replaced everything I could in the carb, including the nozzle gasket. I assume the nozzle is the part that sticks down into the bowl of the carb. There was a flat washer looking gasket that went over this above the float. What is the correct position, is it as far to the butt(top) end of the nozzle as possible?<br /><br />Thanks again for all the help.

 

[prolinews]

Re: 88' 70HP Evinrude, high idle

A freind brought an 83 70hp to me in boxes last year we had a similar problem with the carbs we replaced everything in them . We caught hell getting the linkage correct there is a slim line between perfect and junk on those motors . the motor ran fine for one whole day the next day we started all over again we took apart the carbs cleaned everything twice put it all back together it has run fine ever since I don't know if there was trash in it or the gaskets didn't set right .I would take it apart and try it again compressed air and cleaner some times make miracles.

 

[OBJ]

Re: 88' 70HP Evinrude, high idle

Hi Scott...yes the throttle plates are the ones back in the carb throat. All should be seated closed at idle. The nozzle gaskets are self seating. No right side up.<br /><br />Now there is the possiblity that previous regular idle was caused by a plugged idle jet and when you cleaned the carbs you unplugged it, hence higher idle....that's just a possibility.<br /><br />As prolinews posted, during cleaning, compressed air should be used to blow everything out. During cleaning, soaking in carb cleaner followed up by carb cleaner in a squirt can blown through all passages will do wonders for a carb.<br /><br />Have you done a synch and link yet? This may bring everything together.

 

[scott324]

Re: 88' 70HP Evinrude, high idle

Thanks for the reply.<br /><br /><br />I used carb cleaner and air during the process. I have not lync and sync yet, but I did not change the adjustment. The position of the throttle plates never moved. The rod connecting was removed, but had to go back in the same way. I will play with the idle to see if i can lower it.

 

[scott324]

Re: 88' 70HP Evinrude, high idle

Update:<br /><br />I took another look at the carbs, but didn't see anything wrong. Reinstalled them and idle is down to about 1200rpm. If my memory serves me that is what it was before. <br /><br />How can I adjust the idle if the butterflies(throttle plates) are all the way closed? The idle screw controls the linkage to open and close them so retarding it more does nothing to close them more. The idle screw is not even touching the linkage. The shop manual says ~750rpms is normal. Is this a problem with the starting solenoid leaking fuel after the intial phase? <br /><br /><br />On a side note, what exactly does the nozzle gasket do? It is not held in place by anything and seems to be pretty loose on the nozzle itself.<br /><br /><br />Again guys thanks for all the help. I can see the light at the end of the tunnel.

 

[Solittle]

Re: 88' 70HP Evinrude, high idle

scott - If you are at 1200 running on your trailer with muffs I wouldn't do anything yet. Rpms will drop when you are in the water due to the back pressure. I suggest you try that and see where you are at before you go any further.<br /><br />Might also check the sync & link as JB has suggested & while you are at it might as well check the timing.

 

[rodbolt]

Re: 88' 70HP Evinrude, high idle

the cavity that the nozzle(emulsion tube) fits in seals the gasket to the body. lets go back to basics. why does the motor run at all. cause it has Fuel,AIR and Compression and SPARK. all in the right aount at the right time. open the throttles a bit and you allow more air and fuel. advance the timing a bit and the idle speed will pick up. that system was carefully engineered and tested to perform ata specific idle timing with the carb shutters closed and the correct jets in the carb passages.<br /> if your using the boat tach it may be way off. that is why I have a ferret instruments timinglight/tach. I have found that an idle speed of 900-1000 on the muffs will be about right on the water with those motors. however it still must be checked. sometimes as the carbs fail orthe compression goes south people try to advance the timming or set the butterlies open to compensate so when a repair is made all the adjustments must be checked. thats why I bill at 75 an hour .

 

[scott324]

Re: 88' 70HP Evinrude, high idle

Thanks guys for all the help.<br /><br />Update:<br /><br />I took it out for a test sunday. She started up fine and idled at ~900 in the water. After traveling about 1 mile in the idle zone I went to open it up and couldn't get past 3500rpms and there seemed to be a severe lack of power. This evening I am going to take another look at the carbs. This seems like it might be a problem with the high speed jets? Any suggestions to look for?<br /><br />Thanks

 

[CaptainPuget]

Re: 88' 70HP Evinrude, high idle

Since your symptoms seem to be moving around it would be my guess that all is not clean in the 3 carbs. Your latest problem could be blockage of one or more of the high speed circuits. Then again it could be fuel line or fuel pump related. I’d try the easy stuff first – check the fuel line and tank.