85 50 hp, popping at higher rpms

[sully73]

hi all, i have a 85 50 horce chrysler on my lil capri. last year the boat ran great with no issues. when i fired it up for the first time yesterday, it idles alil rough and when i tried reving it up, it started popping on one cyl when above 1500 rpm. then when i back off of it it wont idle down correctly and continues to pop. all the signs are telling me it running lean and has a airleak somewhere, but i cant seem to find it. the motor has very few hours on a rebuild, and im starting to wonder if maybe the driveshaft seal is leaking by air into the bottom cyl? like i said, it seems to run good at about 1k, but crappy at idle and above 1k. so im guessing that its getting about the right amount of air for that rpm but running lean above, and maybe rich below..?? any help would be greatly appreciated.

 

[tjello327]

Re: 85 50 hp, popping at higher rpms

Could be a simple fuel problem. Fuel can go bad over the winter if no stabalizer was added in the fuel and ran so it gets into the carbs. I would check the carbs to be sure the are not gummed up or plugged.

 

[sully73]

Re: 85 50 hp, popping at higher rpms

i could understand it running like crap with bad fuel, but not idleing down and popping the whole time keeps telling me airleak. to get it to stop and go back to idle, i have to cover the carb for a sec to almost choke it out.

 

[john from md]

Re: 85 50 hp, popping at higher rpms

Popping is actually back firing through the intake. This is commonly caused by a lean mixture or a intake manifold leak.

It is probably a good idea to give the carbs a good cleaning and blow out the passage ways with air. Then run the engine and see how it does.

 

[sully73]

Re: 85 50 hp, popping at higher rpms

thanks guys, i appreciate the advice. im gonna pull the carb and go through it really well. hopefully it doesnt come down to the crank seal. im not even really sure if that could be a problem at all. we'll see after a good carb soak i guess.