Evinrude acceleration problem

[raygussy]

1978 Evinrude 70hp

Hello
My motor has decided to start acting up. It will run good up to about 1/3 throttle then lose power and die. Will restart right away and idle all day. Also starts well cold. Here's what I've done/looked at so far: cleaned carbs completely, they didn't look too bad actually - adjusted carb and choke linkage to service manual specs - gas and oil were fresh at 50:1 - pulled fuel pump and it looked fine - plugs looked ok but I changed them anyway, they were Champions, put in NGK's which did help it start and idle better, but made no difference at 1/3 throttle - checked compression, 120 psi on two uppers, 112 on lower - nice blue spark will arch 5/8" on adjustable checker while turning it over, used an inline spark checker while on the water and still had spark as the motor died, just don't know how good of a spark - checked all of the connections at the power pack and other harness locations - pulled the flywheel and checked for loose connections/signs of shorts - According to the service manual I need a special tool to check the power pack which I don't have. Are there any good tests the average joe can do to test the power pack, stator, etc? Are there any other possibilities you guys can think of? I've exhausted my 2-stroke knowledge and would sure like to have it running again by the long weekend!
Thanks in advance for any ideas!
Ray

 

[DJ]

Re: Evinrude acceleration problem

1978 Evinrude 70hp

Hello
My motor has decided to start acting up. It will run good up to about 1/3 throttle then lose power and die. Will restart right away and idle all day. Also starts well cold. Here's what I've done/looked at so far: cleaned carbs completely, they didn't look too bad actually - adjusted carb and choke linkage to service manual specs - gas and oil were fresh at 50:1 - pulled fuel pump and it looked fine - plugs looked ok but I changed them anyway, they were Champions, put in NGK's which did help it start and idle better, but made no difference at 1/3 throttle - checked compression, 120 psi on two uppers, 112 on lower - nice blue spark will arch 5/8" on adjustable checker while turning it over, used an inline spark checker while on the water and still had spark as the motor died, just don't know how good of a spark - checked all of the connections at the power pack and other harness locations - pulled the flywheel and checked for loose connections/signs of shorts - According to the service manual I need a special tool to check the power pack which I don't have. Are there any good tests the average joe can do to test the power pack, stator, etc? Are there any other possibilities you guys can think of? I've exhausted my 2-stroke knowledge and would sure like to have it running again by the long weekend!
Thanks in advance for any ideas!
Ray

You're losing a cylinder for one reason, or another. The easiest way to find out which one is with an inductive timing light. You can rent one at an auto parts store.

Put the lead on each plug wire (one at a time) and run the engine until it starts to act up on you. See which cylinder is losing spark.

If all three continue to spark evenly, you have a fuel issue, most likely a plugged carb. high speed jet.

 

[HighTrim]

Re: Evinrude acceleration problem

If you have determined that she is sparking sufficiently, following DJ's instructions, try spraying pre mixed fuel into the carb throats. Does that pick it back up? Choking it? Pumping the fuel primer bulb?

What is the condition of the fuel line? Not rotting at all? All connections tight without leaks?

Do you have a built in tank? Is the bulb sucking flat at 1/3 throttle? Vent open and clear?

 

[raygussy]

Re: Evinrude acceleration problem

Thanks for the reply!
I have a light like that, an old Sun model my father gave me. So basically check each wire by pulling the trigger and waiting for the light to activate. If it goes out on one cylinder like it has been doing I'll lose the flash, correct? I know I can swap coils if this happens to see if that's the cause, but is there a test for the stator or power pack?

My uncle told me you can run a motor in a 55 gallon drum of water to simulate back pressure for testing. Is this safe for the motor? Otherwise I have to drive about 12 miles each way to try it out on a lake each time.

Thanks!
Ray

 

[raygussy]

Re: Evinrude acceleration problem

I checked all lines and the vent screw and pick up filter on the fuel tank. It's not a built in one. I tried choking it when it does it and it makes no difference. The bulb stays hard as well when it does it.
Thanks

 

[raygussy]

Re: Evinrude acceleration problem

Also, I tried spraying fuel into the carbs and each time it would pick up a little in rpm's but nothing drastic.

 

[HighTrim]

Re: Evinrude acceleration problem

No problems at all running in a barrel, just be sure that the water pump is completely submerged.

What is the stators condition? Dripping or leaking at all?

As far as the power pack, you can test its isolation diodes with an ohmmeter. Do you have access to one?

 

[raygussy]

Re: Evinrude acceleration problem

Thanks Chris!
I pulled the flywheel tonight to check the general state of the stator. I didn't see anything our of the ordinary. No loose connections or anything that looked like it might be arching. Anything else in particular to look for? I do have a fluke multi-meter and am pretty handy with it...an expert by no means though. If you could tell me how to test the pack that would be great! I really don't think it's a fuel problem because I've cleaned everything including the jets and seats.
Thanks,
Ray

 

[DJ]

Re: Evinrude acceleration problem

Thanks for the reply!
I have a light like that, an old Sun model my father gave me. So basically check each wire by pulling the trigger and waiting for the light to activate. If it goes out on one cylinder like it has been doing I'll lose the flash, correct? I know I can swap coils if this happens to see if that's the cause, but is there a test for the stator or power pack?

My uncle told me you can run a motor in a 55 gallon drum of water to simulate back pressure for testing. Is this safe for the motor? Otherwise I have to drive about 12 miles each way to try it out on a lake each time.

Thanks!
Ray

You've got the idea.

Follow Hightrims suggestions on running it in the barrel. DO NOT engage the prop. You'll tear up the prop and the barrel.

 

[raygussy]

Re: Evinrude acceleration problem

So even if I use the barrel, without being able to engage the prop it's still not going to simulate a load on the motor is it? The motor will run like a top and be very responsive while running on the muffs, get it on the water and its a whole other story. Using the muffs or a barrel make any difference?
Thanks,
Ray

 

[HighTrim]

Re: Evinrude acceleration problem

You've got the idea.

DO NOT engage the prop. You'll tear up the prop and the barrel.

But that is how I wash the dog!

The barrel will be a sufficient load for the testing, it is simply backpressure on the exhaust, no need to engage the prop as DJ stated.

Start with the timing light and we can go from there.

 

[DJ]

Re: Evinrude acceleration problem

So even if I use the barrel, without being able to engage the prop it's still not going to simulate a load on the motor is it? The motor will run like a top and be very responsive while running on the muffs, get it on the water and its a whole other story. Using the muffs or a barrel make any difference?
Thanks,
Ray

Barrels are fine for idle diagnosis and general engine health. However, you're chasing a power issue. You can't duplicate that in a barrel.

Do what you can, in the barrel. The true test will be a "on water" test.

Dealers use huge tanks and fit test props. Those props simulate a load but produce very little thrust.

 

[raygussy]

Re: Evinrude acceleration problem

OK Chris,
Will start with the timing light and see what happens. I'll take it out on the water to test it because if I can't reproduce the problem with the muffs I don't think just the exhaust back pressure will enough. Will let you know how it goes.
Thanks again,
Ray

 

[raygussy]

Re: Evinrude acceleration problem

Hey guys,
Just put it on the muffs because I couldn't get to the water, so I don't even know if this will tell you anything. Tried the timing light on each cylinder, good spark on each one. As I throttled the the motor with the controls (not at the linkage) the timing plate advanced, but stopped at the rubber bumper long before open throttle, like it's supposed to I think. The spark advanced with the throttle and didn't seem to miss at all. I did notice the light seemed to grow dimmer as the motor sped up but I think that's because it was flashing so dam fast! I looked at the timing with the light on cylinder #1. At idle it was at about 6 degrees and as I increased the throttle it went up to about 20 degrees, but I didn't want to rev it any more than that. The numbers didn't jump around at all though, they were very steady.
Thanks,
Ray

 

[HighTrim]

Re: Evinrude acceleration problem

Ray, I would try the spark test again on the water, so that you can simulate the conditions that make it die at 1/3 throttle.

If the spark remains constant, you must have a fuel restriction of some kind. When you rebuilt/cleaned the carb, did you physically remove the jets, clean them with a few strands of wire, and run compressed air through them? Best way to clean them.

Was just thinking as well, any chance that the black/yellow kill wire is grounding out somehow at 1/3 throttle? Maybe take the remote control apart to inspect??

 

[raygussy]

Re: Evinrude acceleration problem

Thanks for the reply Chris!
I kind of figured the boat was going to need to see the water, but I thought I'd try it anyway. When I did the carbs I took out both of the jets and seats, sprayed out the passages with carb cleaner, blew through them with the compressor and visually inspected the orifices where I could to insure no blockage.
When you mention the black and yellow wire I'm pretty sure you are talking about inside the throttle/shift control box. I'm thinking you are trying to rule out something inside the control box grounding out a wire when the throttle physically gets to that same point each time. Good idea. I will look at that tomorrow. I'm also going to look at the fuel pump. After looking at the sticky at the top of the forum page I feel more comfortable pulling it apart. Could that be the culprit in your estimation?
I really appreciate the info. you've given me!
Ray

 

[HighTrim]

Re: Evinrude acceleration problem

The black wire with yellow stripe is the "kill" wire. You can find a wiring diagram of it here VVV

http://continuouswave.com/whaler/reference/ignitionSwitch.html

Usually a failing fuel pump can be remedied by pumping the fuel primer bulb continuosly, thereby bypassing it, since you are doing the work for it. Cant hurt to try.

Let us know what you find.

 

[raygussy]

Re: Evinrude acceleration problem

That makes sense, now I know why people told me to try pumping the ball when it started to hesitate. I'm going to pull the cover on the throttle control to check the wires then take it back out on the water to check spark with the light.
Thanks!

 

[raygussy]

Re: Evinrude acceleration problem

Ok Chris,
Here's what I found:
All three cylinders still have good spark as the engine is dying on the water at around 1/3 throttle. Confirmed it with a timing light. I tried choking it again as it was dying but it made no difference. Here's the weird part. Someone told me to clean out the bulb again just to make sure. So I removed it while we were anchored and it let me blow through it one way and not the other like it should. I put it back on, primed the motor and started it again, and it took off like a bat out of hell!
????????????????
I ran it wide open for about 5 minutes and slowed up, then when I tried it again it died at 1/3 throttle again, and every time I tried it after that. It almost seems like some kind of flow restriction. I've changed the filter on the fuel pump, cleaned all of the lines out, I don't get it. I tried pumping the ball and choking it as it starts to die, neither makes a difference.
By the way, I did check the throttle to make sure no wires were getting grounded out inside the control box, everything looked fine.
Talk about confused!!!
Ray

 

[HighTrim]

Re: Evinrude acceleration problem

How old are the fuel lines and bulb, and what is their condition? They may be deteriorating from the insisde. If the bulb is non OEM, I would replace it with stock. All connections tight? Is this a built in tank or a remote tank? Just curious about an anti syphon valve sticking in a semi closed position, they are notorious for that. Also ensure that the tank vent is clear.