1974 Johnson 40 problems ^^

[wordmaster]

Hello,<br /><br />I have a 1974 Johnson model 4081-745 serial number J4035803 that is about to drive me crazy. I have replaced the points, condenser, primary coil, both pickup coils, spark plugs, rebuilt carb, replaced all questionable hoses, replaced gas hose, and possibly a few other things I can't think of right now. <br /><br />It has good compression, both cylinders the same. However, every time I crank it, it is a new adventure. It might run perfect at high speed, cut out bad at idle or run perfect and cut out at high speed. It might run on both perfectly from idle to high speed or it might just run on one...could be either the top or bottom that is running at any given time. <br /><br />The repairs, except spark plug replacement have bee done by a dealer. They just keep coming up with new ideas for expensive parts to be added or repairs to be made rather than any good diagnosis. I have looked hard and long for anything that might be obvious to my untrained eye (I have done a lot of work of car engines, but very little on boat engines) and the only possibility I have is that a few times, the shifter has locked and moving the flywheel releases it so that it shifts again. This seems to be related to what I assume (but don't really know) is the timing advance, a thingy sticking out from under the flywheel with a cluster of wires attached to it that moves left and right independently of the flywheel.<br /><br />Any and all help would be greatly appreciated. Also, if anyone could give me the part numbers for the correct coils and spark plugs for this engine it would be very helpful. Thank you.

 

[jessieb]

Re: 1974 Johnson 40 problems ^^

Hi i had the same problem with a 25 johnson you might want to change the plate the points go on it might be moving side to side causing the points to miss fire (open to much or not open enough) try holding it and move it from side to side if you have any movment side to side you need to change it, trust me i faught mine for three months 5 different mechanics,but it seems only one of them knew of this problem.

 

[wordmaster]

Re: 1974 Johnson 40 problems ^^

Thank you, that is what the mechanic suggested, but it is just the latest suggestion in a long line of expensive guesses from him. At least I have some corroboration on this one. Does anyone have the part number for that plate the points sit on for this motor?

 

[markjewell]

Re: 1974 Johnson 40 problems ^^

Don't just go out and buy the plate. Jessie's<br />point was to see if there is excessive play side to side in the plate to throw the point gap way off, and possibly throw coil gap off. Check it first

 

[jessieb]

Re: 1974 Johnson 40 problems ^^

yea check it first, sorry if i miss lead you but you should check it first but there is a very good chance that is your problem.<br />cause the plate sells for about $150.00 you should be able to find a used one for about $60.00

 

[wordmaster]

Re: 1974 Johnson 40 problems ^^

Yes, the mechanic said there was a little play in that and that the points could open and close more than they should. Can this really cause all these problems? Any idea where a used one might be found? Thank you for your help.