1973 115 johnson lack of power almost all of the time under load

motor idels great

Re: 1973 115 johnson lack of power almost all of the time under load

is fine in gear at idle and alittle above but seems to struggle at full throttle coils?

Re: 1973 115 johnson lack of power almost all of the time under load

Been like this since you got it, or is this a recent development?
What recent maintenance has been done on this motor?

Back to basics:
Compression test.
Spark test (not a "spark plug" test): get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's not firing in the hole under heat & compression.

Report your results.

Spark plugs in good condition? Are they the correct Champion plug correctly gapped?

Throttle valves parallel?
Choke plates open except when choke is engaged?
Fuel fresh?
Tank free of water/debris?
Fuel line holding pressure?
Tank vent open and clear?

Re: 1973 115 johnson lack of power almost all of the time under load

Do the easy checks first, compression and spark, then on to the fuel delivery system.

Re: 1973 115 johnson lack of power almost all of the time under load

Since it idles good, I doubt the coils would be the problem, (but, then again, it could be). It sounds to me like you need to do a carb cleaning/re-build and maybe some new plugs while you're at it. It takes a good running motor to idle good so, there isn't much wrong with it.

Re: 1973 115 johnson lack of power almost all of the time under load

I have seen those engines idle pretty good on 3 cylinders.

Re: 1973 115 johnson lack of power almost all of the time under load

Daviet said:

I have seen those engines idle pretty good on 3 cylinders.

Click to expand...

not to mention which, who among us hasn't had a cylinder drop out upon acceleration.

Re: 1973 115 johnson lack of power almost all of the time under load

ok so this is where i am i changed the plugs opened the carb on top clean as a whistle. problem of dieing under way seemed to be getting better i had perhaps two seconds of of great running then wanted to die right out oh yeah i also put a new primer bulb on and checked the lines for leaks and changed the fuel . now i think the top carb neddle valve is sticking cause whene i squeze the primer gas pors out of the little holes in the front of the carb so im to the point of pulling the carbs off my 135 same make and year and i looked after i pulled them off there is two brass tubes in the holes at the front of the carbs that arent there in the other ones. missing? could that be the problem? oh yeah i can rev it as high as i want in neuteral does not die.

Re: 1973 115 johnson lack of power almost all of the time under load

The V4 motors can sound fine with no load and be running on only two cylinders.

Get the compression readings and use an inductive timing light on the running engine so that you can tell if you are getting fire at all RPM on all 4 cylinders.

The high speeed jets are located behind the four drain plugs in the bottoms of the float bowls and are easily fouled.