Ignition Problems, Bucking, Only run at low speed/idle

[Neptune422]

Hi All,
I have a 1991 20HP Evinrude (E20CRLEIE) which is having problems...

The motor starts up fine (pull start).

The motor will run at full speed for about ten minutes from start. At some point, around the ten minute mark, the motor immediately stops running at full speed by bucking (rev up to full then down to almost out, non stop until throttling back) then will only operate at fast idle until cool again. If I give it more throttle then just idle amount, it will buck, making me want to chuck it into the river. It sounds like: rum! rum! rum! rum! At that point, it will run for how ever long I need it to but only at the fast idle speed, higher amount of throttle and it will induce the problem.

At idle, it runs rough. At WOT it sounds normal.

Carb seems fine especially since it will run fine from cool for 10 minutes every time. And it will still run at hot just not at full speed. It's getting (gas).
While running it, I disconnected each spark plug one at a time. With the top cylinder disconnected it still ran, and had a strong spark that bridged a wide gap. With the bottom cylinder disconnected it stopped running but showed signs of a strong spark before it couldn't bridge the gap. It's getting (spark).

Whatever the problem is, it happens when the engine gets warmed up.
So I feel like I narrowed it down to the ignition...
Does this sound like a likely cause of such a problem?
There are four components:
The two ignition coils seem OK because each cylinder has spark. The motor can run with the top cylinder unhooked, but it cuts out if the bottom spark plug wire is pulled; there is spark when it's being disconnected. Can one bad ignition module stop the motor from running at full speed? When they are both hooked up it runs...
Then under the flywheel there are the power pack and charge coil...
I am thinking that when the power pack heats up it stops working at full speed...Does this sound like a reasonable cause of my problem?
I will replace the charge coil because it's on the cheaper side at the same time I replace the power pac$... Do you fellow forum members agree that the problem is most likely the power pack?

Thanks!

[boats.net]

Need to check voltage output of charge coil, trigger coil and power pack with a peak reading voltmeter at time engine is loosing power to tell what ignition part is bad.

[fcmartin]

I recently had the same problem and it tired out to be the thermostat was bad causing the motor to overheat and go into a SLOW mode. Check your motor temp when it starts to cut out and if you can't touch the head without burning your self then it is overheating.

[darkgoatracer]

It sounds simple but did you try loosening your gas cap? If the fuel tank doesnt vent properly it can create a vacuum inside the can, and once the vacuum gets to be to much it cant pump fuel

[Neptune422]

Gas Cap DarkTrace: The gas cap happens to be one of the first things I checked because I had remembered I left it on tight at first, and I was excited that that was the problem. Unfortunately, at the ten minute mark (approx), it happened again, and I was back to the drawing board. I saw a crack in the gas tank housing where the line connects with the quick connector so I epoxied it closed to no avail. If it was pulling air the engine wouldn't even run. I have had that pulling air problem happen one time before with a different engine (1987 6hp Evinrude) and fixed it by tightening the connector to the gas tank. Also I think if the can were not able to vent (let air in) the engine will not run at all because the carb would be empty too long because of fuel starvation. I can run the engine seemingly forever at low speed. Hopefully someone will read this one day and the gas cap solution will fix their problem.
THANKS FOR THE INPUT!

[Neptune422]

Fcmartin: I like your suggestion about the thermostat. Why? Because the problem is clearly happening when the engine gets hot; plus you say it was the same thing for you. Yes it could still be the ignition module but this is an easier fix (I think), and a lot less costly. Plus it makes a lot of sense given that the problem is totally conditional on how hot the engine is. If I let it cool down for awhile I'll get maybe only 3 to 5 minutes of normal full speed because it already has some residual heat.
I ran the engine till the problem happened then took off the engine cover while it was running and put my hand on the back of the engine. It was real hot. I checked the repair manual I bought as a solid repair guide, and it says my model engine shouldn't run hotter than 160 F. The manual has a mistype saying "must be exceed 160 F" but I'm pretty sure they meant 'must not exceed 160 F'. I don't have a digital thermometer. I'm getting one for these times when I need to know ($25 to the doorstep). So when I held my hand to the engine I really couldn't keep it there more then maybe 2-3 seconds at most because it was that hot. I realize that 160 F is hot, but a lot of things that I read say the same thing, if you can't keep your hand on the engine when it's hot, it's too hot. Water is always peeing out, and it looks like plenty, but maybe it's not getting to the part of the engine that needs it because the thermostat doesn't open...
I just pulled the trigger on a bunch of parts and gaskets to get this engine back to normal. The thing is that I ordered the thermostat and the spring and the gasket but I didn't order a new over heat switch...I mean it clearly works if this is the problem...but to replace the thermostat I have to take off a big plate and take out a lot of screws, the switch is under there, too. Does anyone think it's important to put in a new switch while I'm at it, even though the current one is working, because I'll have it apart anyway? I really don't want to buy unnecessary parts...I just want to go for a full ride for once and not have to worry!
THANKS FOR THE INPUT!

[jada631]

Neptune, Any luck with changing the thermostat and overheat switch? I have read your posts with great interest as I am experiencing same problems on my 2001 150hp.
Have a look on YouTube:
150Evinrude.MPG - YouTube

[Neptune422]

jada:
I saw your video. I'm not sure you captured all the symptoms on tape. What I was looking for was to see your engine run normal at idle throttle. If it will run normal at idle, then you just might have a temperature problem which results in the engine going into 'slow' mode.

[Neptune422]

PROBLEM SOLVED

I found the problem! Hopefully it will help someone in the future fix their problem, too.

I got my order from boats.net in a timely manner. It was 98% accurate. One of the plastic bags that contained an oil seal ($6) was empty. The bag with the part number was in the box the order shipped in, but the bag itself was empty. It looked like the bottom of the bag just wasn't sealed all the way across. It's a lightweight part so the person packing my order probably didn't realize it was empty just looking at the front of the bag. I called customer service, they said they are going to send it to me. Called again to follow up and they said it was being sent out the next day. I'm taking the time to write my minor complaint because I had to put my engine back on the boat after I repaired the main problem I was having. Anyone who has taken an outboard off their boat knows what a pain in the *ss it is. I'll have to take the motor off again to replace an oil seal within the lower unit I didn't have when I needed it ( I spent hours making my list so I wouldn't have this problem). Maybe I'd be taking it off anyway given that I still need to do one more thing...

OK:

I got my laser thermometer the day after I took the motor off the boat so I never got to check the temperature of the motor while the problem was happening before I replaced the thermostat; I had only used my fingers as the temp gauge.
I replaced the thermostat, the cooling chamber gasket, and did not replace the temperature switch ($32). The cooling chamber looked in decent shape while I had the cylinder head cover off, not a lot of build-up. The thermostat looked dirty, kinda of old, you know, used. I had no idea if it worked or not, but it was not stuck open and I wasn't about to play games with it and boiling water (1. below).
I put the motor back on the boat with new plugs, thermostat, couple of gaskets, fuel pump diaphragm, zip ties... Taking the cylinder cover off, really the cooling chamber cover, was no problem. I had put the motor on a stand I built.

I was very excited to try out the motor now that I had replaced a bunch of parts and everything looked good. At around the 13 minute mark the problem started again! I was disappointed to say the least. I wanted the motor to be fixed real bad having never gone out on even one full ride, bummer times ten.

But now I was armed with my laser thermometer I had put off buying for so many years. These things are awesome. Point it anywhere and it shows you the surface temperature. You can check wires looking for heat, walls looking for heat i.e. missing insulation, air conditioner air temp, but most importantly, the temp of my engine while it was having the problem. In the shop manual for my engine it says NORMAL OPERATING TEMPERATURE OF MY ENGINE IS 160F. Shooting the cylinder head plate the reading was around 152F, perfect. I used my fingers like before and I couldn't keep my fingers there without feeling like they were going to burn (2-3 seconds). So just be aware that 160F, which is NOT the operating temperature of ALL motors, some are 130F-ish, is hot and you might not be able to tell if overheating is your problem this way. Now I know my motor is NOT over heating. WTF

On the way back to the house I had my nephew steer while I took the cowling off and stared at the motor wondering which expensive part was next to replace. We were going back at idle speed. I decided to check something while I had the cover off. I decided to unhook the temperature switch while the motor was running. I unhooked it, the motor continued to run, gave it gas and nothing changed. But now the switch wasn't even hooked up and it still ran. I had never really thought of unhooking the switch, I thought the motor wouldn't run without it hooked up.

Later that night, while it was becoming dark out, I wanted to go for a 10 minute ride I knew I could get before the problem started again. I wanted to cool off from all the engine work and just enjoy the water for whatever time I could get. I started my stop watch, and went out. I turned around early, 4 minute mark, so I could return at full speed. I got back around the 8 minute mark and it was still running normal. I decided to go back out 2 minutes to squeeze out a little more time. Got back around 13 minutes and it was still going. I decided to go back out again, returned around 16 minutes, still going. Went out again, returned around the 23 minute mark, still going strong. Then I remembered I never hooked the temperature switch back up. I stopped, put it in neutral and took off the cowling, shot the back of the motor with the temperature laser, and it read 156, perfect! It was NOT overheating. The switch was BAD. That's it! It was the switch!! The switch was sending the signal falsely that the engine was overheating, putting the motor into 'slow' mode. Once the circuit gets the kill signal it goes into 'slow' mode and won't return to normal until after the motor is shut off, possibly even having to disconnect the battery if you have one.

BIG SHOUT OUT TO fcmartin!!!! for taking the time to help out a fellow boater!!! You helped me save time and money by giving me that lead. More than I can say for the boats.net guy... If I had waited for them to answer I would have maybe had my engine strewn across my floor looking for ohms instead of on the back of my boat working.

So the answer to my question: should I replace the switch while I have it apart is yes. It's a cheap part considering you'll have the area open anyway. I never would have known it was the switch if I had replaced both at the same time. I would have thought it was the thermostat. And a big point is that you probably can check if your engine is complaining of overheating by simply unhooking the switch. If unhooking the switch fixes your problem your problem is probably related to overheating. The switch is there for your protection! Don't leave it unhooked if you don't know the proper operating temperature of your engine, it might be the thermostat and if you leave it running when it's overheating because you disconnected the switch, it could blow the whole en$ine. Better to get back slowly at idle than ruin your motor.

I'll order the switch and put it in. But in the mean time, while I know the engine is not overheating, I'm loving going for 1 hour+ rides!

I get 5 gallons of gas at a time. My calculations tell me I'll get about 2-2.5 hours out of that tank; about $10 an hour to run. This engine is a piggy.


1. To check if a thermostat works:
Remove the thermostat out of the motor. When taking it out, check to see if it is in the open position. If it is stuck in the open position, it's broken. A thermostat will open when it works, not close. If you are in an emergency situation where the motor is overheating you can take the thermostat out, put it back together and see if this fixes the problem until you can get a new thermostat ASAP. You would be letting the engine run as cool as it could by taking it out. This messes up the efficiency of the engine and should not be left that way.

A) find out the operating temperature of your motor
B) Get a thermometer that can be used in water and goes up to at least the operating temp of your motor
C) Put the thermostat in a pot of water
D) Heat the water until the thermostat OPENS
E) Look at the thermometer, if it reads the operating temp of your engine when it OPENS it works
R) If your thermometer reads higher than normal operating temp when it opens it is broken
R) Or if it does not open at all and the water boils, it is broken.


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