evinrude 115 idle problems

Krazywayne

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Joined
Dec 13, 2013
Messages
2
I have a recently rebuilt 115hp 1983 evinrude that will not idle. It will crank and run fine as long as the warm up lever is raised. As soon as you lower the warm up lever to normal idle position the motor back fires from exhaust and dies. I have rebuilt the fuel pump and the carbs and installed new fuel line,filters,and fuel. I can raise the warm up lever to raise rpm and hold the carbs open manually and as soon as the lever reaches the normal idle position, same thing, backfires and dies. I have an idea it may be timing issue but fear the reed valves may be bad. Any suggestions?
 

Bob_VT

Moderator & Unofficial iBoats Historian
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May 19, 2001
Messages
26,019
Re: evinrude 115 idle problems

There are marks on the carb linkage for startup. make sure your cables are adjusted.

The carbs can be VERY picky and the low speed passages clog very easy. The jets do too...... rebuilding them is good and making sure you have not sucked up some crap/debris through the fuel lines is important. It will run on only 2 cylinders and unless you check.....your ears will never hear the difference.

Have you checked the power packs, the compression and the spark? About the only things that can go with the reeds is being stuck open with debris or a broken one. If you pull the carbs they are visible.

The backfiring and poor idle are really ignition indicators and I would concentrate there first, check the coils. Use a timing light.

The 83 motors are really pretty bulletproof and easy to work on.

Welcome to iboats!!
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: evinrude 115 idle problems

It's always possible that the engine is out of time. It can get that way when the flywheel key shears. Usually, however, when that happens the engine won't start at all. Yours does and it may be close to correct timing. Also, VT is correct. If the idle passages in the carb become clogged with dried fuel or other debris, it won't idle at all. You indicate they've been cleaned: were the idle jets removes and the idle passages blown out with an aerosol carb cleaner? It can run at mid rpm's and abruptly stop when returned to idle.
 

Krazywayne

Recruit
Joined
Dec 13, 2013
Messages
2
Re: evinrude 115 idle problems

Thanks guys, I am by no means a mechanic and I bought the boat from a buddy. I am positive the carbs are okay. I had another friend mention the sheared pin on the flywheel but have not had a chance to check that. I also have replaced a bad coilpack and I will do all the checks on the spark and compression next time I get a chance to work on it(prob Sunday) The motor as been passed from buddy to buddy to me and they all had problems with idle. What should proper idle rpm be, 750?
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: evinrude 115 idle problems

If you had a bad reed, you'd probably see some fuel spraying back out the carbs on each stroke. You didn't mention that. Proper idle would be 650-700. Set when the boat is floating normally in the water and it's in forward gear. Probably idle about 900 or 950 in neutral in the water. You can't set it on the trailer-there is no backpressure (from the depth of the water.) On the trailer it might idle between 1100 and 1200-maybe slightly higher.
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: evinrude 115 idle problems

Try a cylinder drop test on it and see if you can nail it down to any cylinder/s.
 
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