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8 hp Evinrude issues under load

toothvet

New member
Greetings! Thank you in advance and sorry if this is too long, but I am trying to provide details to get the best info. I am back after solving a previous issue with the help of this board contributions.

I have a 1993 8 hp Evinrude that I recently posted about the carb cover. After getting the motor back, I was able to cross reference the number on the cover and it was indeed from an earlier model as one member suggested. I replaced it and got it running well. I took the boat out (12-foot aluminum boat) and ran 16 mph and was pleased. Loaded the boat up and ran the fuel out of the carb (also run Stabil).
This last Friday, 2 weeks since the last time, I went out to fish and was facing a strong headwind with small white caps. The boat seemed to run smooth but would only get to 8mph and felt like the RPMs would only go so far even with throttle fully applied. I stopped and took it out of gear where it ran up and held high idle as well as all ranges in between (smokes a lot in this circumstance). I was thinking this could be due to the higher load, but I do not have much experience with small boats like this and don’t know what is expected. After 20 minutes or so of running this way, the motor seems to struggle and run rough. Again, I took it out of gear and was running fine. Not wanting to push things farther, I shut it off and begin to fish (caught 8 little, large mouth, one on the first cast). I was drifting with the wind and using the trolling motor. After the fish quit biting (a couple hours max), I fired the motor up and ran 16mph back with no more issues. The wind had died down, so no big advantage but definitely less load. I ran the fuel out and now wanting to look through the motor, change the lower gear oil and inspect for issues.

The fuel tank is vented properly. The bulb goes firm before starting and is not firm when running but can make it firm for a bit. I can restrict fuel flow and it will run up then stall.

I am trying to figure out if this headwind would be expected to make that much of a difference?
What would make the motor run rough after running under a load for 20 minutes or so then run fine with less load after a couple hours?
What should I be looking for?

I am hoping to go out again in the morning if I can make some progress today.

Thank you again!

Chris
 
The wind really has noting to do with it.-----Test run with another hose and tank.-----Could be an air leak on the hose or inside the tank.----Could be water in the fuel.
 
Thank you racerone ! I can see where this would be a potential cause. Can you help explain why it was fine on the way back? Is there a way to test it vs buying another fuel tank and line? The tank is older and I recently replaced the pick up as the previous one broke off. I also replaced the connector since the spring loaded valve was not sealing.

An air leak could be anywhere in the system too, so I will inspect all fuel lines. I was thinking it would a be a consistent issue if that was the case.

Chris
 
Test run on a calm day.----How old is the water pump impeller ?----Compression test values are ?----Spark jumps a gap of 3/8" on a test device ?
 
Its been a while, I sold the boat with the 4 stroke I bought and now revisiting while trying to get this ready to sell. I ran it in a barrel of water and revved high and stayed there. No way to really load it up.

I have answered the questions below. Already replaced fuel tank and line.

How old is the water pump impeller ? not sure but great stream from tell tale

----Compression test values are ? both are 100 with motor warmed up

----Spark jumps a gap of 3/8" on a test device ? I pulled spark plug wire, inserted screwdriver and it jumped an inch. I don't have a tester.

Thank you again!

Chris
 
As far as I'm concerned, with those smaller motors wind and waves COULD slow you down significantly. If the motor sounded fine, I wouldn't lose sleep over it. if it really did sound like it was struggling how's the water flow?
 
Don't ever underestimate the power of wind and water.
Many years ago, my wife and I and two small kids were in a small 12' with a 6hp Evinrude.
We made a return trip at the wrong time. Big mistake! We were fighting the incoming tide in a rather narrow section of channel. No wind.
My wife started yelling at me to look at the shore. We weren't moving. We barely made it through. Took 20+ minutes when it should have taken 2.


Jim
 
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