speed problems with my 1968 evinrude

[ceasarea]

I bought this great little 40 hp electric start i believe 1968 evinrude....no electric shift ...not a big twin. The guy told me to run it with a 40/1 oil/ gas mixture....It starts and purrs great. However i have a speed problem. It was running nice and fast but now only runs at a slow speed even when the throttle is fully open.I cleaned the filter as well as replaced the gas hose and spark plugs.( .20 as was on the fly wheel). I am ruuning it on a 1961 crestliner falcon 14'....so it really should fly !...Any help is appreciated.

I should also add that when i changed the spark plugs ( changed to the same ones as on the motor....6j6 i think .....look like lawnmower spark plugs), the top one was fairly clean but the bottom one had black oil on it.

The problem inititially started this way....It would run fast and plane well for a few weeks but every once in a while you could feel the motor moving the boat faster ...sometimes for a few minutes and other times speriodically. Then i decided to tow a tube with my daughter on it. She is 12...so fairly light. After an hour or so of fun it slowed down and has never returned to full speed. It runs smooth and starts beautifully but just wont get up to speed.

Since i just bought the motor i havnt done a compression test.Also i love this motor...and probably want to restore it to its original condition...any ideas or comments? Ex...will it be way to expensive?

 

[oldcatamount]

Re: speed problems with my 1968 evinrude

Sounds like you need a carb cleaning/re-build.

 

[ceasarea]

Re: speed problems with my 1968 evinrude

Than you ....The giuy i bought it off is a diesel mechanic....he said he rebuilt the carb already....But who knows.

 

[bktheking]

Re: speed problems with my 1968 evinrude

Check for spark on BOTH cylinders.

 

[Tim Frank]

Re: speed problems with my 1968 evinrude

I cleaned the filter as well as replaced the gas hose and spark plugs.( .20 as was on the fly wheel).

Usually the spec on the flywheel is the points setting....and .020" sounds about right.
Spark plug gap would be more likely .025-.035"....someone will know, or check the owner's manual.

 

[ceasarea]

Re: speed problems with my 1968 evinrude

Usually the spec on the flywheel is the points setting....and .020" sounds about right.
Spark plug gap would be more likely .025-.035"....someone will know, or check the owner's manual.

Thank you......i actually gapped the spark plugs at .20....i dont have a nanual...but need to get one...When i changed the plugs , both had seen better days, however the bottom one was quite wet with oil.

 

[kbait]

Re: speed problems with my 1968 evinrude

Gap new j4c plugs at .030". Check spark with a tester. Sounds like you either have a bad plug, or coil/points for the lower cylinder are bad.

 

[F_R]

Re: speed problems with my 1968 evinrude

It is a mighty safe bet that it is running on one cylinder. Get that flywheel off and check the ignition system. Having "spark' doesn't impress me much.

But before you do that, have you checked the compression? No point in doing anything to it if the compression is not good.

Most carburetor problems---aren't.

 

[ceasarea]

Re: speed problems with my 1968 evinrude

compression is good in both cylinders.....probably need the points and coil looked at in the spring.