1984 40 horse Johnson Outboard....has no power!!!

[Flyboy8784]

Hey guys.....Im kinda new to boat ownership....but been fishing and on boats all my life...ill give you the whole run down..hopefully someone can help.

I bought a 1955 aluminum open bow runabout (14 foot) with this 40 horse Johnson on it.

After a ton of money and alot of work restoring it we finally got it in the water last week.

However....at WOT there is maybe half throttle....ive searched a bunch on here..and tried a few things....both plugs were covered in oil....i replaced them yesterday then the starter solenoid blew

the motor runs a little more balanced....but still no power....what kills me is that the thing SCREAMS in my driveway at WOT...the minute it gets in the water...it bogs down..and we have to crank the idle up just to keep it from shutting down.

The boat itself is light...I figure its easy to say i should be getting at least 30 knots out of it...i think im lucky if im getting 15.

My only last guess is that the fuel/oil mix is way wrong....but could that really bog down the motor that much???

Please Help guys!!!!!

 

[tx1961whaler]

Re: 1984 40 horse Johnson Outboard....has no power!!!

DO NOT let your motor "scream at WOT" in your driveway. You will quickly destroy it that way.

The first things to check are the compression and spark, with a spark tester set at 7/16". One you have confirmed that the spark and compression are OK, then you can move on to the fuel system. My guess is that one of the cylinders is not firing....

 

[shorehugger14]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Beyond the above mentioned checks it is easy and cheap to rebuild the carbs, that is what fixed my '85 evinrude 40. Definitely make sure compression and spark is good first. You run a great risk of shattering a piston if you run your motor above 1800 rpm off muffs, if your compression numbers are say 120/35 then you can assume you have done some damage. Good luck and I hope your comp #'s are high and with in 10% of each other. Post your results and you can get a good idea on the next course of action.

 

[Flyboy8784]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Thanks for the heads up guys....i should have mentioned....i am running the muffs on the motor....and WOT is for less than 5 seconds when i do it.

Compression will be tested tomorrow....ill be sure to post the numbers so i know what we are looking at.

Any particular reason why the motor would rev up higher in reverse than in in forward??? again that was noticed in the water....

 

[shorehugger14]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Five seconds WOT on muffs is five seconds too long, trust me, I did the same thing and ended up repalcing my motor because the top piston shattered.

 

[Flyboy8784]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Aight guys....compressions running around 110 PSI on both sides....i know its low......but at least both cylinders are working


Any other thoughts????

 

[shorehugger14]

Re: 1984 40 horse Johnson Outboard....has no power!!!

If the spark is good to both plugs then order the repack kits for the carbs and repack/clean them, it is easy and only takes a couple of hours. It is good news that your compression is good.

 

[tx1961whaler]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Was the spark test OK?

 

[DutchMerc]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Check the ignition with a scope, you need to be sure all plugs are firing. You need the scope to check if the timing is good. This looks like a problem with the ignition...

 

[Flyboy8784]

Re: 1984 40 horse Johnson Outboard....has no power!!!

Alright...havent spark tested yet....thatll be done on friday since im workin all day tomorrow....i was also told to buy a tach too....makes sense....I got an uncle coming over on friday who knows all about it to help me....thanks alot so far guys....i really really appreciate it