no power under load

[murphdog]

i have a 1986 johnson 25 horse that starts fine in the drive and runs fine in the drive yet falls on it's face when under a load any help?

 

[Backlash]

Re: no power under load

Usually a sign that one or more of your cylinders is not making power. With the motor running under load (in the water of course) pull one plug wire at a time and listen for a difference in how it sounds. If the cylinder is making power, you'll notice the motor will run worse/stall out. If no difference, that cylinder is not making power. Check each cylinder individually (maybe more than one bad). After determining which cylinder(s) are bad you can troubleshoot.<br />Backlash

 

[kevkc123]

Re: no power under load

I'd definately check compressionon both cyl's and if OK, move on to ignition problems. Plugs, plug gaps, wires, and timing probs can all be fixed easily with a MANUAL.

 

[murphdog]

Re: no power under load

I did a compression test both cylinders were very close at 125 psi and both seem to be firing fine also my seloc manual says gas oil mix should be 100:1 I have always mixed at 50:1 could this be the cause of loss of power under load?

 

[cobra 3.0]

Re: no power under load

No. 50 to 1 is better for your engine. I believe Johnson/Evinrude 'corrected' themselves and stated 50 to 1 was better.<br /><br />What does 'fall on its face! mean? Does it bog down or just die? If it bogs down, it sounds like its not getting any fuel.

 

[murphdog]

Re: no power under load

it starts fine and will run great for awhile then it starts to boog down and then will die it only does this under a load in the drive with muffs it seems to be ok

 

[DJ]

Re: no power under load

murphdog,<br /><br />Any multi cylinder two cycle engine will run great-with no load.<br /><br />Once you load it (in the water) something is dropping out. Since you have one carb. look at the ignition first. I suspect you are dropping spark on one cylinder when under load.

 

[murphdog]

Re: no power under load

thanks guys off on friday I guess I will take it out on the water is that when I pull the plug wires one at a time and see if there is a change in the way it runs?

 

[kevkc123]

Re: no power under load

Check ignition coils(if applicable)! I had some prob. and it was a bad coil.. oops-- forgot to mention that before! <br /><br />KC

 

[murphdog]

Re: no power under load

ran the boat today on the lake started fine ran good for about 3 miles wide open or at idle then started to bog down until it stalled got it started again but would only run rough checked both plug wires seems to be firing fine the bulb on the gas tank went soft pumped it up again and she took right off all the hoses on the engine have plastic ties could it just be sucking air and loosing its prime I will change the gas line fittings and bulb at the tank and motor should I change to clamps on all fuel lines or would this not make a difference

 

[mikehoustontx]

Re: no power under load

Murphdog,<br /><br />Another thing you can try is putting some of your fuel mix in a squirt can and give the offending cylinder carb a shot or two. This may help you confirm or eliminate a fuel issue. Do this under load at the lake; not with the muffs.<br /><br />I would think that, under normal conditions, the bulb would go soft after running awhile. Initially, you pump it up to have fuel available at the fuel pump. The bulb's internal check valves close to hold the fuel in the line to the pump. After starting, the vacuum pulling the fuel from the tank to the pump should keep the check valves open.<br /><br />By the way, how old is the rubber in the fuel pump? A rebuild kit from a dealer should be about $12. It's about a 20 minute job including refreshing yourself with a cold one at the ten minute mark.<br /><br />Hope this helps.<br /><br />Mikehoustontx

 

[reeldutch]

Re: no power under load

i think the vent of your fuel tank is clogged.<br />check for dirt in the tank or use a portable.

 

[Bass Runner]

Re: no power under load

If the vent on your tank isn't plugged i'd bet you have a fuel pump problem. Just a thought.

 

[Cricket Too]

Re: no power under load

murph....what do you mean by you checked both plug wires and they seemed fine? Did you see any difference in the way the engine ran when you had either of the plug wires off?

 

[Solittle]

Re: no power under load

My money would go to crud in the carb that requires cleaning and a rebuild kit.

 

[Bass Runner]

Re: no power under load

A simple check, pull the pickup out of the gas tank there is a strainer on the end of it make sure the screen isn't plugging up, i had a piece of a plastic gro. bag get in the tank (from god knows where) it rapped around the pickup once in a while and you would go dead in the water, like to have never what was causing it, after rebuilding the whole fuel sys.