70hp johnson bogging then stops

[QSS]

hi guys i have a 70hp johnson 19820model that boggs down under load but only sometimes i,ve replaced fuel, plugs, checked timing,compression. it only seems to do it after a good run at wot. i bring it back to idle then hit the throttle to wot again and it stumbles and either comes good after a few seconds or cuts out. is it time to pull the carbs and overhaul? or poss an ignition problem? any ideas would be appreciated.

 

[HighTrim]

Re: 70hp johnson bogging then stops

I would probably start by using a timing light to determine if she is firing and there is spark.

Will pumping the primer bulb pick her back up? Choking it? Spraying pre mixed fuel into the carb throat?

 

[QSS]

Re: 70hp johnson bogging then stops

Yes after priming the bulb it came good so my problem is fuel but would i be looking at fuel pump or ??

 

[QSS]

Re: 70hp johnson bogging then stops

does this sound like i,m on the right track with the fuel pump guys or?

 

[tashasdaddy]

Re: 70hp johnson bogging then stops

fuel pump, air leaks, i fuel line. when were the carbs last cleaned and rebuilt? have you done a link n sinc? when you mess with timing, you have to link n sinc afterwards.

 

[ezeke]

Re: 70hp johnson bogging then stops

Did the primer bulb seem overly soft when the engine died?

 

[BigJ08]

Re: 70hp johnson bogging then stops

Start by doing a carb job. Sounds like something really similar to what my 65 hp was doing a while back. Clean the carbs really good (every small piece and orifice), and give it a try.

 

[QSS]

Re: 70hp johnson bogging then stops

yes done a link and sink,primer bulb was soft,and i have not yet done the carbs. so i,l go do the carbs and put a kit in the fuel pump and try. does this sound write??

 

[HighTrim]

Re: 70hp johnson bogging then stops

USUALLY having the engine pick up when priming the bulb is an indication that the fuel pump is weak, as you are manually feeding the carbs, doing its job.

I would also look to ensure that all fuel line connections are tight, and that there are no air leaks present from rot. If the fuel lines are original or aged, replace them. This will save you many headaches.

Are you using a portable tank or built in tank? If built in, you could run a portable tank to rule out issues with the tank vent and anti syphon valve. If the problems dissapears while running on the portable, look to these spots to start.

 

[huckelberry]

Re: 70hp johnson bogging then stops

Check to make sure that the carb valve-es close when coming off plane from wot. there should be a linkage that keeps timing between the carb-s and the magneto. It can hang up, all the way open, and when you throttle down off plane, the carb will flood motor will bog and then shut down. It is spring loaded and should hold itself closed pretty easily.