All of a sudden it runs like poo poo...

[craigman]

Fellas,
1974 Merc 85hp. Been running great,,, untill today. Went out to start it and didn't want to start. When i did eventually get it running, it ran like garbage. Backfire, try to run backwards, idle very ruff, ect.. Put in new plugs and same thing.
Have any ideas what to look for? Same tank of gas, so no change their. Like i said,, been running great. Started right up like a champ. Only sat for about a week since last taken out.
Any ideas you can throw my way would be great!
Thanks!
Craig

 

[KCinNC]

Re: All of a sudden it runs like poo poo...

only thing i can thing of is maybe the fuel filter ?

 

[Gomer50]

Re: All of a sudden it runs like poo poo...

I would seafoam it,maybe some stuck rings,check the carbs and possibly some dirt got into the reeds preventing them from operating correctly.Also check the compression.There are so many possibility's,trigger going bad switchbox,coil etc.I guess do a little check off list of the things mentioned here and post back

 

[craigman]

Re: All of a sudden it runs like poo poo...

Fuel filter is new.
Seems to be getting plenty of fuel. I even wonder if it's getting too much fuel.
I took both carbs off, cleaned very well with carb spray, all passages seem clear.
I can get it to run, but it's hard start, and pops and backfires. And at high rpms, it misfires.

Any ideas!
thanks!
Craig

 

[achris]

Re: All of a sudden it runs like poo poo...

Start with the standard stuff...

Check compressions.
Check you have all sparks and they are nice and strong.
Check you have fuel in the carbs and the choke is closing.
Check that the starter motor is spinning the engine the right way.
Check you have the right leads on the right spark plugs.

It's all very basic and should be the first things you check, any time there's a problem....

Chris........

 

[Gomer50]

Re: All of a sudden it runs like poo poo...

I might have an answer,I have a 1972 Merc.800 and this happened to me as well hard to start and misfire/backfire at higher Rpms.Take your distributor cap loose and pull it down so you can see the rotor.Nr1 check your carbon thingy in your distributor cap.Nr2 now this was what was wrong with mine on my distributor the part shown in the red circle had come loose therefore interupting spark and eventually no spark.I hope this will not be your case because either way this is exspensive.

 

[craigman]

Re: All of a sudden it runs like poo poo...

Thanks fellas!
I'll recheck all the basics.
Also i'll check the dizzy.
I'm almost wondering if the timing belt could have slipped.
Tomarrow is another day.

Craig

 

[Gomer50]

Re: All of a sudden it runs like poo poo...

Please post back with your findings.Our motors are pretty much Identical,I have owned mine for about 2 years and I am constantly fixing something on it.I have had issues with the timing and I am am still not too happy with its performance.I guess what can you expect from a 40 year give or take motor.I dont run so swift either anymore lol......

 

[craigman]

Re: All of a sudden it runs like poo poo...

Yep, i'll post back whati find today.
I've been very happy with mine. I've only had it out a few times this year, but it's ran like a champ every time. Always started great, idled great, could troll at an idle for an hour, wouldn't load up, just been flawless untill now.
I'm still thinking either the carbs or timing. But me and a buddy are going to start with the basics, compression, timing, ect. and go from their.

I'll let you know later this evening what i come up with!
Thanks again,
Craig

 

[sschefer]

Re: All of a sudden it runs like poo poo...

I'd be looking for something heat related. By that I mean something that got hot the last time out and when it cooled became damaged. Could be something as simple as a wire that's now touching ground and shouldn't be.

The best method for finding your problem will be to follow the Service Manual trouble shooting procedures. That's what a Mechanic would do even if it was obvious because the obvious is not always the root cause.

 

[craigman]

Re: All of a sudden it runs like poo poo...

Just a quick report..
Have checked all the basics, timing, compression, ect..
Later today i'm going to run it and mess with the mixture needles on the carbs. Almost seems like a lean pop.
More digging!

Craig

 

[craigman]

Re: All of a sudden it runs like poo poo...

Welp, it runs better now.
Seems like i had a wire from the distributor grounding out. I THINK i got it fixed.
Time will tell...

Craig