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1990 evinrude 8 hp miss or surging @ wot

Put 2 hrs on the engine today, about half @ full throttle. Engine is a 1990 E8RESR, idled great, no stalling or hesitation going to full speed. As this engine had been stored since 2003, I figured on a few issues. 1st startup ran it in a garbage can with a fuel line in a gallon jug, seemed to run good enough to buy it. Getting it home it seemed to run ok @ low and medium rpms, any faster and it would slow down and eventually quit, as if it was running out of fuel. Pulling the choke would not keep it running ( @ this point it was hooked to a standard 6 gallon tank and line ). Got repair kits for the fuel pump & carburetor, redid both ( did not see anything amiss with the carb ). The fuel pump ( thank god for the instructions included) pretty much the same. New w/p kit and we were good to go today. What I'm not sure about is, does this engine have a rev limiter on it? Does it have electronic ignition? It doesn't seem like a fuel problem, more like stumbling, when you back off the throttle it clears up. Few items: filter screen @ pump cleaned, float level checked ok, new correct plugs installed ( pulled after today's run look good, no fouling) , ran with cap loosened on tank in case vent wasn't clear. That's about all I can think of. I know it's hard to diagnose over the computer, but appreciate any help. If anyone read my post abt the rewind spring for this motor my entire fishing career was powered by DD 6-71s & 8-92s none of that is helping me now. Thanks for reading, Jersey Bob
 
Hi Jersey Bob,

Your motor has CDI ignition.
Did you completely disassemble and CLEAN the carburetor?
Also did you check spark with a spark gap tester (similar to Lisle 50850)?
What spark plugs did you install? Looks like recommended spark is a champion QL77JC4. Did you check plug gap before installing?

I'm no where near as experienced as others here on the forum, but if it were me I'd check to make sure I cleaned the highspeed jet well and that I'm getting good spark.

The more specific information you can provide the better people here will be able to help.

JG
 
Test run it at full throttle on the lake.----Operate the manual fuel pump when motor falters and see what happens.
 
Johnny is onto it. These " newer" motors have a fixed high speed jet. They HAVE TO BE CLEANED TO CORRECT ORIFICE SIZE, or motor will starve at high speed. Please see my adjacent post on the same subject.
 
Timguy, to date everything suggested has been done. I ran a copper wire thru thru the main orifice ( jet) which is the original .050. I considered running a #55 drill ( .052 ) thru it, but didn't. Float height was correct also. New QL77JC4 plugs with .030 gap installed, good spark. Surge, stumble, miss? is only @ WOT, and is intermittent. As i don't have access to a hand held tach, I have no idea what the engine is turning @ WOT under load. Propeller is the Evinrude suggested 8.5"D X 9"P 3 blade. Thanks for not giving up on me, Jersey Bob
 
Have you had the motor cover off while it was running to check for high pressure leaks? Is it possible one or more of the fuel lines is smaller diameter than it should be?

Also, as racerone said, did you try pumping the fuel primer bulb during the stumbling condition?
 
Bob, can you try out a completely different tank and hose. Your rig could be sucking air, or bad check valve in the $15 "synthetic" squeeze bulb. You would think our engineers would use pure natural rubber in critical components.....eh? Like impellers. Natural rubber is not suitable, however, to endure alcohol "infected" fuel. Over 70 percent of "rubber" out there is synthetic now. Don't ever think your tires are real rubber anymore.....they are not. That's also why you should replace your impeller every 5 years, they are made out of "plastic" now. WTF? THE ORIGINAL IMPELLER
is still working perfectly in my 5 1/2 hp Johnson Sea Horse......1954. Do you think I want to change it yet? ........that's when the trouble starts. Still has the original siamese fuel/air supply lines wow! Now THAT'S ENGINEERING!
 
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Have you had the motor cover off while it was running to check for high pressure leaks? Is it possible one or more of the fuel lines is smaller diameter than it should be?

Also, as racerone said, did you try pumping the fuel primer bulb during the stumbling condition?
Yes to both suggestions, all lines checked, oem diameters, no leaks
 
That's okay now, how did the old one look? Save it for your spare. Question for Bob, did you try the different hose and tank if you can find one?
 
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Bob, can you try out a completely different tank and hose. Your rig could be sucking air, or bad check valve in the $15 "synthetic" squeeze bulb. You would think our engineers would use pure natural rubber in critical components.....eh? Like impellers. Natural rubber is not suitable, however, to endure alcohol "infected" fuel. Over 70 percent of "rubber" out there is synthetic now. Don't ever think your tires are real rubber anymore.....they are not. That's also why you should replace your impeller every 5 years, they are made out of "plastic" now. WTF? THE ORIGINAL IMPELLER
is still working perfectly in my 5 1/2 hp Johnson Sea Horse......1954. Do you think I want to change it yet? ........that's when the trouble starts. Still has the original siamese fuel/air supply lines wow! Now THAT'S ENGINEERING!
Tim had the opportunity to borrow a tank with a new hose off a 15hp Evinrude that runs great today. Within 15 min underway, same problem. I'm not giving up hope, can still use the boat, just can't keep it on plane, which puts a bigger load on a small engine and wastes a lot more fuel. It was suggested to check the wiring as it moves due to advancing the throttle but saw no evidence of chaffing. Thanks, Jersey Bob
 
Any possibility you didn't put the fuel pump together properly? There are a lot of potential things to get wrong. I had to try a second time to put my fuel pump back together last year.
 
Any possibility you didn't put the fuel pump together properly? There are a lot of potential things to get wrong. I had to try a second time to put my fuel pump back together last year.
Same with me, it leaked when I first reinstalled it. from the back. Looking at the instructions again, I had not installed the back gasket, because it was not used on some original pumps. Instructions advised to use it, I did, no more leak. Pump seems to be fine
 
Some simple testing required.------Run with cowling off to see what happens.------No money spent .------Run with a timing light hooked up ( out on the river ) and observe spark on both leads when motor falters.----Again no money spent.
 
Some simple testing required.------Run with cowling off to see what happens.------No money spent .------Run with a timing light hooked up ( out on the river ) and observe spark on both leads when motor falters.----Again no money spent.
I know I'm showing my age, but how do you power a timing lite on an engine that doesn't need a battery? 55 years of commercial boats w/DD 6-71s & 8-92s has me with a disadvantage now. I was telling a friend the only outboard i ever used until 3 wks ago, was 63 years ago. A 3hp Johnson with an built in tank, and you had to turn it 180 to go astern. Thanks, Jersey Bob
 
You put your 12 volt riding lawnmower battery in the back of the boat.----Hook the timing light to the battery.-------Clip the timing light to the sparkplug lead.------Test run the boat.
 
Trying again. Had a thought, when rebuilding carburetor, noticed that brass tube on the nozzle holder was open on the top and was not the same on the bottom of the holder. Is this a restricted opening? I was able to get a needle in it, no dirt or debris at all. I couldn,t understand if there is a .050 main orifice (jet), why the opening in the tube that supplies fuel to the main body of the carb would be smaller dia. This part is no longer available, so I have nothing to compare it with. Maybe there is an issue here? Thought this might have a bearing on my problem, or I'm chasing rainbows while waiting to get the boat out after the weather breaks. Thanks Jersey Bob we'll se if this post makes it.
 
I think part of the fuel is diverted up that stupid little tube for the low speed circuit. This carb was engineered by retards.....sorry had to say it....like kids playing around and no direction from a responsible adult.
 
I think part of the fuel is diverted up that stupid little tube for the low speed circuit. This carb was engineered by retards.....sorry had to say it....like kids playing around and no direction from a responsible adult.
Tim, can I gather that in this case there is no need to go back into the carburetor, as this has nothing to do with the high speed circuit? Would be fine with me, as I don't feel like dealing with the recoil starter spring again
. But if deemed necessary will do. If necessary, any thoughts on running a #55 ( .052 ) drill thru the main jet or wait til I get this squared away and find out what the engine will turn @ wot under load? Thanks Tim. JB
 
Yes I'd hold off with drill until you get things ironed out. They should be fine with that 50.
Tim, I thought abt what you suggested, and remembered that the tube just supplied the idle circuit, and the brass tube that goes up to the middle of the carburetor throat is the high speed circuit. So no need to go over that. I can't see this being fuel related at this stage, had the boat out, flat calm, idled and great up to wot. I'm beginning to suspect a high speed miss? Although I thought I had good spark ( I used a spark checker, not a spark gap checker). This could make a difference? This still is an intermittent issue, back off the throttle a bit and it disappears. Thanks, Tim for following up on this for me, JB
 
Checking spark for continuity can be a step in the process, but you need to check to see if the spark will jump a 7/16" gap to prove it's working well. A real bright white/blue lightning snap.
 
Checking spark for continuity can be a step in the process, but you need to check to see if the spark will jump a 7/16" gap to prove it's working well. A real bright white/blue lightning snap.
Just picked up a spark gap tester, now I know why everyone should have one, Adjusted it according to the manual @ 1/2" gap, not only saw it jump the gap, I heard it SNAP. Don't know what to think now. It would be hard to put a regular spark tester on the engine while running and see what's doin', can't lean over the stern of a 12' aluminum boat underway without putting her under. Where do I go from here? Thanks to everyone who's staying interested
 
Just picked up a spark gap tester, now I know why everyone should have one, Adjusted it according to the manual @ 1/2" gap, not only saw it jump the gap, I heard it SNAP. Don't know what to think now. It would be hard to put a regular spark tester on the engine while running and see what's doin', can't lean over the stern of a 12' aluminum boat underway without putting her under. Where do I go from here? Thanks to everyone who's staying interested
If I'm doing this right, it will be a P.S. Is it possible that I am experiencing some cavitation at wot? The wheels that we used on our boats are 36"dia and will only turn 1050 shaft rpms. Now I have a 8.5" dia prop turning I don't know what, with the engine @ say 4000 to 5000 rpms. Is there a reduction gear in the lower gear casing? Don,t laugh, just showing my lack of knowledge. If so are cavitation plates used (or necessary) on these small engines? Thanks JB
 
Cavitation can be a problem if the prop isn't deep enough in the water, but you would know if there's a cavitation problem by the sound of it. I don't think cavitation is your problem, just look up some videos on outboard prop cavitation to hear some examples. I don't think an 8 hp would have much benefit from an extra cavitation plate, that flat metal piece that sticks out a couple inches near the top of the gearcase is the onboard cavitation plate.
 
??-----You would turn the flywheel and see if prop turns the same amount.------But I make easy again.-------Flywheel turns 29 times and during that time propeller turns 13 times.
 
??-----You would turn the flywheel and see if prop turns the same amount.------But I make easy again.-------Flywheel turns 29 times and during that time propeller turns 13 times.
Waiting for the wind to die out, get some more time os this engine. At this point, I don't no much more I can do. I did find that the throttle adjustment were way out of whack and the engine was never reaching full throttle. Waiting on a hand held tach so I'll know what wot truly is on the water. I can only imagine that the issue will be worse if it will turn up more than previously. Will be back after the next trip, be happy if anyone may have any other suggestions that I haven't tried. I appreciate all the information I have received, I've learned a lot this past week, thanks to everyone's interest. Thanks, JB
 
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