motor problems

C

Chris L.

New member
just would like to say thanks to all for the abundance of info on this site and i have yet another ? for u guys i have a 25hp evinrude 93 yearmodel tiller handle that runs at all rpms except idle and for the life of me i cant figure it out it idles great on the trailer with muffs i have pulled the idle needle and seat and cleaned them good the motor idles fine for a short time and then seems like it loads up or something cant really tell and after it does this it miss fires makeing a coughing sound i think . which if its idleing and u dont have your hand on the throttle to adjust . it cuts itself off with this missfire and if u rev the rpms a little it will cough fall on its face a few stokes and smooth back out there is no rythym to it just seems to smoke a little more when this happens

now i thought i had it figured out but i was wrong . i thought the foam in the cowling wich was falling apart into tiny pieces were getting sucked in but thats not it i removed the foam and ran it today with the same results also already swapped out spark plugs and the old ones didnt look bad but i replaced them any way

the only thing i can figure now is gas to oil ratio wich is 50 to 1 and i use good oil also use stabil in all gas
i did try it with out stabil with same results . i found a few people on internet that said evinrude recomends 100 to 1 but i would like some reliable info b fore i try such a lean mix

this motor starts on the first or second pull everytime and runs like a sewing machine except for this problem
(wich is a p.i.t.a. when setting out decoys or picking them up ) and it only does it in the water not on muffs i idled it at the house for thirty minutes and it was smooth as silk the whole time putt it in water and it only takes seconds to happen als when u ran a while at higher rpms and slow to an idle it takes maybe a few minutes before it starts

anaybody have n e i deas as to the problem i am banging my head
 
yes i am doing more digging right now and found that post 1960 smaller hp that they did recomend the 100:1 but they changed it later and it is 50:1 i was thinking maybe timing but that would have the same results o the muffs also maybe compression but i have never seen a motor run that good with out good compression its almost like the motor is fireing on the exaust stroke but i dont really understand that so im back to asking for help
 
Chri for what it is worth , here is what i would look for , and air leaks Like vaccum lines or fule hose issues ? Maybe a pluggged fuel filter ? bad bulb ? Just a few things to look at .


Good Luck


Dave M
 
I am no mechanic, but that sounds more like an electrical problem. Do you know anyone that has the tools to test your power packs, stator, check your spark, that kind of thing?
 
First off-DON'T EVEN DREAM ABOUT 100:1. I see you have already gotten good advice on that acount. One difference in the running on the "fake a lake" is you don't have any back pressure on the exhaust system. That may not help you find the problem but explains the difference in running on the muffs and in the water. I suspect that you have a fuel problem, by that I mean stale ethanol fuel doesn't run well and at idle it is even worse. Good luck, you have lots of company with the crap we have to run.
 
Are you seeing a good water stream when running in a lake versus the muffs? The muffs have constant water pressure to push the water up to cool the motor...if your water pump impeller is shot, you won't get a "pee" stream out the back of the motor in a lake condition and it may be a high temp shutdown
 
It sounds like you may have a thermostat problem. If you can get a look at the cylinder heads and there is any browning on them it's running hot. If so that's why it's stalling at idle.

The power packs are infamous for crapping out on them too.
 
I had the same problem on a mid 80"s johnson 20hp. The push pull primer/choke on the motor has a small hose that runs to the carb was loose. I found it by using the primer with the cover off and wiggling the hose . It didn't really leak untill i wiggled it. I also rebuilt the fuel pump. I think it is fuel related also. Just wanted to add that the problem wasn't that it leaked gas but it was sucking in air at idle and low rpm.
 
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it may b a fuel problem but all the fuel is new and i have no idea about the powerpaks i appreciate all the advice and i will go through it again this afternoon looking for any leaks and all that if thats not it ill b calling a mechanic to take it too over it
 
Chris
replace all of your fuel lines, ( not a big cost, any auto parts place will have them) and check all of your wires to make sure none of them are dry-rotted Replace them if you can.. Any fuel fittings with 90 degree turns clean them out with carb or brake Kleen and a small wire . I did this to my motor with the same problem and runs great now. Also get a new fuel pump for the carb again not a big cost.
Jeff
 
I don't know how other people feel about Champion plugs but I and My brother will not use them.He is a maintenace supervisor for a large landscaper in the area and anything that comes in with Champion plugs get Autolites in them.We both have had nothing but trouble with them.For myself,many years ago, I bought a welder/generator with an Onan engine and from day one I had trouble starting it.With a pull rope to start this thing,it didn't take long to get tired and PO"ed.After years of fighting with this, my brother told me replace the plugs with Autolite's and since then, two pulls is all it take,even after sitting for a long time,since I don't use it much lately.Once it was running it ran good,but starting it was a (word for female dog insert here)
 
Robert, I agree with your thoughts on Champion plugs but differ on your solution. I try to put NGK's in everything, years of working on Japaanese motorcycles has reenforced that belief. Wish I had an answer for the Champion problem but it does seem to be out there.
 
Robert, I agree with your thoughts on Champion plugs but differ on your solution. I try to put NGK's in everything, years of working on Japaanese motorcycles has reenforced that belief. Wish I had an answer for the Champion problem but it does seem to be out there.
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I have the same year and size of motor branded Johnson and I had the same problem. It turned out to be the brand of plugs. Switched it up and it runs fine. I will have to check to see what brand it works best with but I do know it is fussy.
 
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