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1994 15HP Evinrude Inconsistant Idle Problems

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Abelinkkin

New member
I am having a couple interesting issues with my '94 15hp evinrude.

The first problem is that when sitting at idle in neutral, the engine will slowly start revving up on its own. It doesn't go very high but there is a noticeable change in idle speed. It will stay like that for a few seconds and slowly idle back down. Any ideas on what can cause this?

The second problem is when switching from idle to forward/reverse the engine will just immediately die. The only way i can get it to shift into gear without dying is to rev the engine way up in neutral before shifting (which i know is not good for the motor)

I already have plans to take the carb apart and clean it but any other suggestions would be helpful. Thanks.
 
Turn the rich/lean adjustment about a 1/2 turn counter-clockwise (more rich) and see if that improves both problems. Sounds like you are running too lean. Could also be crud in your slow speed jet. A seafoam treatment by adding it to the fuel might un-crud it if the adjustment above does not work. If it does work, report back and we can help you get that adjustment perfect. Running too rich is not a good idea either.
 
Abelinkkin said:
I am having a couple interesting issues with my '94 15hp evinrude.

1 - The first problem is that when sitting at idle in neutral, the engine will slowly start revving up on its own. It doesn't go very high but there is a noticeable change in idle speed. It will stay like that for a few seconds and slowly idle back down. Any ideas on what can cause this?

2 - The second problem is when switching from idle to forward/reverse the engine will just immediately die. The only way i can get it to shift into gear without dying is to rev the engine way up in neutral before shifting (which i know is not good for the motor) Thanks.
Click to expand...

Abe,

1 - That problem is caused by a leaning out of fuel, such as when you run a engine out of fuel.... just before it runs out, it will increase in rpms. Fuel restriction, fuel/air leakage somewhere between the pump and the supply, fuel pump starting to fail.... something on that order.

2 - At idle, remove one spark plug wire from the spark plugs, one at a time to see if the response is identical. Do a compression check to see what the psi readings are. Do you (with both spark plugs removed) have a spark that will jump a 7/16" gap with a strong blue lightning like flame... a real SNAP!?

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4



Let us know what you find.
 
Thanks for the replies all.

I finally got a chance to work on the motor a bit more last night.
  • Took carb apart and cleaned & put in repair kit
  • Replaced both spark plugs
  • Replaced fuel lines from the inlet to the fuel pump and from the pump to the carb
  • Checked the fuel filter and looks good

Put everything back together and it started right up and ran great. After about 5 minutes the idle suddenly increased and the motor died just like joereeves said happens when it runs out of fuel. Tried for a couple minutes to start it back up and couldn't. Then I noticed that the fuel bulb from the tank was almost empty. Pumped it a few times and BAM, started right back up. So it seams my fuel bulb may be bad and not letting fuel flow to the engine causing the idle to vary and stall.
 
With the motor running you operate the bulb on the hose.-----------------If there is no change then the fuel pump is working OK.--------------If motor falters and you operate the bulb and it runs and runs and does not stop, then fuel pump on motor is faulty.---------Repair kits , new diaphragm is available for that pump.
 
In pumping the fuel primer bulb, you are acting as a manual fuel pump.

The fuel primer bulb is usually laying in a horizontal position on the deck somewhere. As such, when the engine runs, the fuel in the primer bulb drops to the halfway mark... the bulb DOES NOT stay hard... this is normal.
 
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