40HP Johnson has NO POWER!

[bitbull]

Maybe somebody can give me some advise. I have a 1968 40hp Johnson, the fuel system seems just fine and I just did a carburetor kit / job and changed the sparkplugs. It runs nice and smooth. Ok the problem is the power -> THERE IS NO POWER. At full throttle it moves my 16' fiberglass (it's pretty light) at a wopping 5 knots. My 9hp kicker does almost 6 knots. I'm stumped.... Please some advise. thanks

 

[dsinger]

Re: 40HP Johnson has NO POWER!

What kind of RPMs and what is the compression.

 

[Frankhanhart]

Re: 40HP Johnson has NO POWER!

As you did a carb-rebuild, maybe you put the linc & sink out of whack. Good luck

 

[Paul Moir]

Re: 40HP Johnson has NO POWER!

Besides compression, check spark. Should jump a 1/4"-3/8" gap on both cylinders. Perhaps you're dropping one due to coil arc-over, etc.

 

[Silvertip]

Re: 40HP Johnson has NO POWER!

An engine that performs that poorly is probably not running on all cylinders and will shake like crazy. Do a spark check. An engine needs fuel, air, spark, and it all must happen at the proper time. You are missing one or more of these.

 

[bitbull]

Re: 40HP Johnson has NO POWER!

Spark is ok, it starts up and idles and revs up just fine with no shaking. I didn't do a compression check, other then turning it by hand which seems like pretty good compression. There's new fuel. When it is time to go it is just plain slow. Max 5 knots. Would there be a problem with the drive train or prop (the prop is not chipped or broken tho). Please help

 

[Paul Moir]

Re: 40HP Johnson has NO POWER!

Did you test spark with a 3/8" gap? Both plugs please.

Can't be a driveline problem unless the engine is revving up real high.

While your at it, describe the firing ends of the spark plugs. They should be the same, damp and tan or brown.

 

[bitbull]

Re: 40HP Johnson has NO POWER!

I'm going to check on the spark plug gaps and get back to you.

 

[bitbull]

Re: 40HP Johnson has NO POWER!

ok, now it won't start again. and on one spark plug it is oil soaked and the other one is clean.... please help me as I will not give up

 

[Paul Moir]

Re: 40HP Johnson has NO POWER!

Which plug was oil soaked, the upper one or the lower?

Since they're not the same, it's likely not carburation. That leaves ignition, leaky fuel pump (hence my question), possibly even a blown head gasket though that I think is least likely.

 

[bitbull]

Re: 40HP Johnson has NO POWER!

it is the lower spark plug

 

[Paul Moir]

Re: 40HP Johnson has NO POWER!

Shouldn't be the fuel pump then since it's connected to the top cylinder.

Ignition, possible head gasket. Should be able to test both those things.

 

[dstoica]

Re: 40HP Johnson has NO POWER!

Hi bitbull, I have an identical problem on a 67 evinrude 33HP and was wondering if you found the actual cause and remedy and if you could post it here. I have seen many posts related to this problem but no real cause / solution and I am totally puzzled.

Thx. dan.

 

[F_R]

Re: 40HP Johnson has NO POWER!

The possible causes are all listed here already. Don't assume. Check each one and you will find the problem. My money is on it's running on one cylinder. My best guess is you have some bad coils. Now it's up to you to find out if I'm right. But check the compression 1st. Don't assume. Forget the carb, that isn't the problem. Don't assume.

 

[klicknative]

Re: 40HP Johnson has NO POWER!

Check the plug boot and terminal. Had one come apart on my '69 Evinrude Lark.

 

[vision2000]

Re: 40HP Johnson has NO POWER!

Maybe somebody can give me some advise. I have a 1968 40hp Johnson, the fuel system seems just fine and I just did a carburetor kit / job and changed the sparkplugs. It runs nice and smooth. Ok the problem is the power -> THERE IS NO POWER. At full throttle it moves my 16' fiberglass (it's pretty light) at a wopping 5 knots. My 9hp kicker does almost 6 knots. I'm stumped.... Please some advise. thanks

 

[clint]

40HP Johnson has NO POWER!

It sounds like water is entering into the bottom cylinder from a blown head gasket. Check compression in cylinders. If plug becomes crystal clean after running, the heated water is cleaning your plug. If it's not firing you would have a gas soaked wet brown color plug. Smell the plug for gasoline.
JP

 

[bitbull]

Re: 40HP Johnson has NO POWER!

Ok, I replaced the ignition coils and spark plug wires. It helped alot but there are still issues.

Now I can start it up and let it idle. But only if the start lever is pulled back. If I put it up it will stop. Anyway I can also rev up the the rpm's on the engine when in idle (by moving the throttle arm on the carb), but when I'm in gear on the water it still has no power / speed. At full throttle (with the control lever all the way down, and the carb throttle arm all the way open) I am only getting about 5 knots and the engine is not really reving up, (it sounds like low rpms.) Please help

I checked the compression ->
Upper cylinder = 105 psi
Lower cylinder = 115 psi

Also how can I check the rpm with a voltmeter?

 

[bitbull]

Re: 40HP Johnson has NO POWER!

Oh and also, I had set the engine sychronization and linkage adjustments acording to the shop manual book instructions, but they seem odd. Can somebody please tell me how to set them. please and thank-you.

 

[o/b tech]

Re: 40HP Johnson has NO POWER!

You may also have a faulty cut-out switch. This cuts out a cylinder in case of an overspeed condition. It is operated by vacuum pulses form the engine and grounds out a set of points if this condition exists. May be a faulty spring or diaprhagm in the unit. Try disconnecting the electrical connection from the switch.