1974 85hp merc outboard running problems???any help would be great...

[ranger31]

Here is the deal,85hp merc thunderbolt ignition..Just got it back from the marina and it had a lot of work done..Now has the same problem it had in the beginning..I like to restore boats and rarely take a motor to a mech...the motor compression is acceptable.The plugs,wires,cdi,and wiring harness have all been replaced,and from overlooking their work all is checking out..The motor starts as should,runs pretty dam good now that I rebuilt the carbs..When it is running it will simply stop..Mostly in the higher rpm range when the warm up lever is in the upper position(guessing around 2200 rpms)I have run test after test on fuel,spark and electric and cannot see an issue..I have come up with the conclusion that it could be something in the key or ignition in the control box???Any one ever heard of this???I actually have a video that you can see on you tube so as soon as I download it you can hear/see what I am talking about..Well any help greatly appreciated..thanks again.. OK SO NOW YOU CAN GO TO YOU TUBE AND SEE WHAT I MEAN,TYPE IN (1974 MERC IGNITION PROBLEMS) IN THE SEARCH AT THE TOP OF YOUTUBES PAGE..YOU SHOULD SEE MY VIDEO AND DOWLOAD IT IS A 5:00 MIN VID,THANKS GUYS....

 

[mike1245]

Re: 1974 85hp merc outboard running problems???any help would be great...

theirs a safety switch inside thew control box maybe thats whats shorting out

 

[Moody Blue]

Re: 1974 85hp merc outboard running problems???any help would be great...

Your diagnostics are not very methodical. Just kept repeating the same sequence over and over.

Once the motor stalls, will it restart with the fast idle lever raised? You kept lowering it before starting.

Can you increase the rpm with the throttle lever instead of the fast idle lever? Does it still stall?

Try pumping the primer bulb while increasing the rpm and see if it still stalls.

When the motor stalls, don't touch anything. Measure the voltage on the WHITE wire on the non-distributor side of the switchbox. It should be +12V. Measure voltage on the RED wire same side. Also should be +12V.

Post back with your results.

Is this motor new to you or is this a new problem that just occurred?

 

[ranger31]

Re: 1974 85hp merc outboard running problems???any help would be great...

Yes,it will start back up immediately with the warm up lever up,I have done this numerous times.It will also rev up and down.It appears in the video that I lift the warm up lever around the same place,but it will also quit in any location of the warm up lever up.It will however seem to idle longer,it has stalled at an idle though not common.I am assuming it will quit when in forward instead of the warm up lever simply because it will again and again on the lake in gear.I have ruled out fuel although was my first guess,because carbs have been rebuilt(pro)and then reinspected because of this problem..I have tested fuel,tank,line,fittings,primer bulb with spare,pump,floats,needles,all are checking out..I have ruled out fuel???I also made sure the air idle screws are adjusted correctly..I have not checked the voltage you suggested..I will do that and post results..thanks again...