40 h.p. johnson running issue

gordyB

Recruit
Joined
Aug 17, 2003
Messages
5
my 40 h.p. johnson, i think it is a '73, will run full throttle when in nuetral, but when in gear under load appears to only throttle up about 1/4 power.even with the throttle wide open i can only putt putt around. help me please.........
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: 40 h.p. johnson running issue

gordyB <br /><br />Sounds like you are not getting spark to one cylinder. Even one cylinder that's firing will allow the motor to rev up in neutral without the others firing. Check for spark on all cylinders first. Make sure it is a strong blue spark. Don't rev the engine in neutral to avoid damaging the motor. Just above idle is OK. Let us know what you find.
 

gordyB

Recruit
Joined
Aug 17, 2003
Messages
5
Re: 40 h.p. johnson running issue

thanks rick....but i have spark ...good spark on both cylinders....could it be that it is a fuel problem??...
 

rickdb1boat

Supreme Mariner
Joined
Jan 23, 2002
Messages
11,195
Re: 40 h.p. johnson running issue

Yes, it could be a fuel problem. What do the plugs look like? Dry, Wet, Ect after running it?
 

Mucka29

Petty Officer 3rd Class
Joined
Aug 31, 2003
Messages
87
Re: 40 h.p. johnson running issue

i had a merc like this, spark on all clyinders but no power, it turned out to be a bad coil, once it got hot it wouldn't work, eventally it cracked and i bought a new one
 
Joined
Aug 25, 2003
Messages
14
Re: 40 h.p. johnson running issue

this sounds like the same trouble i'm having w/ my '78 55 rude. i'm thinking its the bottom coil as well.
 
Joined
Sep 7, 2003
Messages
1
Re: 40 h.p. johnson running issue

Gordy, please let me know if ya get your running right. I have the same problem on my '74 Johnson 40hp.
 
Top