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1997 40HP Evinrude cuts on and off

J

joefishin

New member
"My 1997 Johnson starts fine a

"My 1997 Johnson starts fine and runs fine to begin with.....
But after running it near or at WOT for 8 to 10 minutes......it start shutting off....and starting right back. Constantly on for a couple of seconds...then off for a couple of seconds, on and off. I can back the throttle down to about 30%........and it runs fine. I can let it cool down and it runs fine until it warms back up.......then it's on and off, on and off.

I put a new fuel pump on it. Disconnected the overheat wire. And put in new spark plugs. Still does it. What can it be?"
 
I am having the same problem w

I am having the same problem with my 50hp jerry if you here anything or i get mine fixed first i will let you know.
 
I just put a new coil on it to

I just put a new coil on it today. The old one had a thick oily substance around the plugs. If this does not work....I am taking it to the dealer to put on the dynamo meter. Will let you know.
 
"Either the engine runs hot, o

"Either the engine runs hot, or You have a faulty temp switch. It is the SLOW kicking in.
Change impeller, check/change thermostat (vernatherm) to be sure cooling is enough. When You are 110% sure the engine is NOT running hot, disconnect the temp switch and test."
 
Thanks for responding Morten..

Thanks for responding Morten...I disconnected the temp switch on the last try. It made no difference. The motor is releasing plenty of water from the tube so ...I wouldn't think it was running hot.
 
Did You restart the engine aft

Did You restart the engine after disconnecting? If SLOW is initiated engine must be restarted to get it out.
What kind of spark plugs are You using?
Do another test from cold engine:
Have the temp switch disconnected and the black/yellow stop circuit. Disconnect at power pack.
 
I disconnected the temp wire b

I disconnected the temp wire before I started. I am using Champion spark plugs. This particular problem didn't start until the power pack was replaced and the oil reservoir was disconnected (and wire cut) so that I can mix the gas and oil together.
 
"Replace the power pack again,

"Replace the power pack again, You might have got a faulty one.
Can You see from the plugs which cylinder is cutting out?
Is it the same or is it at random?
If You got a timing light hook it onto plug cables when running and see which one drops out.
Even You cut the oil tank alarm cable, that should not inflict on the slow function."
 
"upon reading your first post,

"upon reading your first post,..backing the throttle back and it runs fine,would make me think it is a wire problem,going to timer base,..pinched wire,broken wire.,wire ends not all the way seated in plug-in boot(not conn good)..etc...the throttle,wont release activation of SLOW.Have u run a compression and spark test?..also,a partially restricted HS jet could cause your problem.(more of a bog down tho).or restricted fuel filter/fuel del problem.(it does fine until it needs more gas)
Like morten says,..u need to determine,if your prob is fuel/compression/or ignition related,then,we can go from there.I have never seen a SLOW, pack prob,cause an instantaneous -on-off-on problem..if all of your conns/plug-ins are good,i would run a continuity test,on the wires going to timer base.if good there,..i would replace pack like morten says.Look in all the conn's leading from pwr pack...may be just bad conn at on of them."
 
I've run a compression tes

I've run a compression test it is fine. I changed the fuel filters early on in the problem and I changed tanks and fuel hose. No help. Put a new fuel pump on it. No help. It seems to be too even of a cutout to be a fuel supply issue. Not like a "bogging down. More like a "on...then off". After 9 or 10 minutes of WOT...the cutout starts. I did notice...I can pull the throttle back to about 40% or so and after a few minutes of running at this speed..It starts cutting out here too. I finally have to back it down to 25% or so to make it back to the ramp.It will fine for quiet a while at this lower speed.

I guess I need to start tracing all the wires.
 
Still won't run.

I retr

Still won't run.

I retraced all wires I could see..checked and replugged into connections. Everything seems fine plus all grounds are tight. It still cuts out. The only thing I haven't done is to disconnect the black/yellow wire as mentioned above...and replace the new CDI power pack that I just put on last week.

I am about ready to run it over a cliff.
 
"do u have a emer kill sw on d

"do u have a emer kill sw on dash,or side panel?..if so,it could be acting up..u can test all that as u know ,by disc the blk yell wire....but,rem,u cant kill it till re-attached."
 
Don't have an emergency ki

Don't have an emergency kill switch. Except for the lanyard. I couldn't see the black yellow wire. It must come up from the bottom or something. ??
 
"the lanyard type sw is what i

"the lanyard type sw is what i am referring to....but,......if this eng runs fine ,then u accellerate,starts losing fire,then as u reduce throttle,the fire comes back,...which,ignition would be instantaneous,then,i would run the continuity tests,on the timer base wires,.BOTH,at idle pos,and the AT WIDE OPEN POS.....if there is a break in one of those wires...it will do exactly...as u r describing...as the timer base rotates,continuity is again made,...fire comes back.......ck for raw/rubbing wires from the timer base,as well,that could ground to blk as u throttle.
Another thought,is a grounding problem,in control box,against ign sw blk/yellow wire.Disc blk/yell at eng will ck this area."
 
"then its back to the ign--i h

"then its back to the ign--i have seen wtr in fuel cause a hs prob,like u mention.ck the wires on timer base."
 
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"Pull the flywheel , inspect y

"Pull the flywheel , inspect your triggers and Stator , I think its your triggers ...Trust me on this ..."
 
"overheated,broken wires...I d

"overheated,broken wires...I do think it may be timer base (sensor) prob also. ck cont of wires yet?.u can run ohm's tests on the sensor as well as cranking tests."
 
"It's fixed.

After fir

"It's fixed.

After first installing a new power pack, ...then a new coil, gas hoses / tank, fuel pump and spark plugs....we replaced the "new" power pack. And...it runs fine. So...the new power pack was defective. Thanks for all you guy's advice. I was at wits end."
 
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