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6HP Evinrude with no power

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wallis01

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"I found a filthy 1967 Evinrud

"I found a filthy 1967 Evinrude 6HP is my late father's shop, cleaned it up (now it looks to be in very good condition) and it seems to run fine. After testing, found water in lower unit so had seals replaced. Tested on boat, it starts, idles, runs smooth, but has no power. Removing spark plug wires verified it's running on both cylinders, very smooth, but I estimate about half power (I have a 1981 6HP Evinrude for comparison). Lot's of RPM when it's out of gear. Compression feels same as my 1981 which runs great, but haven't actually measured it. Fuel screen was checked as well as throttle linkage to be sure it was travelling full stroke. Tested with 50:1 mix same as my 1981. Not sure what to look for next. Anyone have any ideas how to proceed?"
 
"If its been sitting around a

"If its been sitting around a carb clean is probably called for, especially if it will run better with a some choke.

If pumping the priming bulb makes any difference it is probably a fuel pump problem.

Also check the fuel filter. (sorry you've done that)

50:1 is the correct mix for all after 1964. The current recommendation for plugs is J6C gapped at 0.030""
 
"Thanks for info. Found choke

"Thanks for info. Found choke acts like throttle up to about 1/2 choke. Removed carb, removed float chamber plate. Carb is cleaner than you can imagine. Looks brand new. Reassembled, checked all screw tightness. Reset idle screw knob to run best at dead center. Pumping primer makes no difference. After all this, runs the same. Compression seems very good. All linkages look like new. I'm at a loss."
 
"Test your compression with a

"Test your compression with a guage, and check your coils. Any chance a weak spark could be the problem? If it still has the original coils, odds are they are failing and aren't giving a good spark. New coils are readily available."
 
"Hi Greg,
just a goofy thoug

"Hi Greg,
just a goofy thought, but since you mention that you have plenty of RPM out of gear and are testing the motor on the boat, any chance the propeller might be the wrong size or pitch?"
 
"Good feedback, guy, thanks. P

"Good feedback, guy, thanks. Propeller is two-bladed, while my other 6Hp is three-bladed, but it looks similar. It's possible coils are breaking down under load, but the engine seems to run perfectly smooth. Just no power. Everything under the cover looks very good, but can't say if the coils are old or not. If coils are failing, I would have expected intermittent misfire. Haven't checked plugs yet, they are M44C. I'll see if I can borrow a compresssion gauge and confirm the cylinder compression. I'll check the plug gap at the same time. It's kind of amazing how smooth this thing runs, but the need for so much choke points to something being wrong. In spite of the super clean carb, I wonder if a jet could be plugged? Or, if timing could be bad because the points are set incorrectly? I'm going to look for J6C plugs. I keep coming back to the choke issue which points to fuel rather than spark, but I'm no expert."
 
""I wonder if a jet could

""I wonder if a jet could be plugged?"

That's what you need to look at when you clean a carb. Give it a good soak in cleaner and then poke a soft copper wire through it. Be absolutely certain it is completely clear.

I don't know how different this is to a 1968 model (possibly no different) but they appear to have had an 8 x 7¼ 2 bladed prop.
Also the plugs listed were Champion J4J, Autolite A21X and AC M42K. In those days they did not seem to just stick to Champions but goodness knows what the current Autolite or AC plugs are so go after some J6Cs."
 
A lot of great ideas. I'm

A lot of great ideas. I'm going to plan an attack on this and will post the results in a couple of days. Thanks all.
 
Running better with the choke

Running better with the choke partially closed is the clue! The brass high speed jet is restricted. Clean it as Vic suggests..... located in bottom center portion of float chamber.
 
"I took carb off again, checke

"I took carb off again, checked HS jet gently with precision PC drill bit as a gauge to find diameter. Used braided copper wire as cleaning brush by removing strands/twisting until it fit. Soaked jet with acetone and cleaned it with wire until it looked clean. Re-checked diameter and definately have increased it. As before, motor runs smooth. Observed that choke linkage on this model increases throttle directly, accounting for "throttle" affect when choke is applied to engine at idle (until point is reached where flooding occurs, about 1/2 choke). I don't think this is a problem. Hopefully, cleaned jet will recover lost top-end power. Did see some small flakes come from jet when cleaning. This is all I can do until I get the motor on a boat, not sure when that will be as I'm not close to water.
I'm very optimistic- thank you all for your help, it was a great learning experience. Happy boating."
 
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