82 mercruiser 260 pops under load

[fstncrnrs]

i have an 82 mercruiser 260 i have rebuilt carb twice then finally broke down and bought a replacement. problem with popping under load still persists. i have replaced points, cap, plugs. carb is a carter 625 it is used but suppose to be in good workin order. popping starts around 2500 rpm. ive checked timing, fuel pressure. cant seem to find ballast resistor so im assuming that its just a wire. i have a voltage drop from battery to coil of almost 5 volts. book says it should only be around 3 volts. if someone has any suggestions i would be greatfull.

 

[NHGuy]

Re: 82 mercruiser 260 pops under load

Chase that circuit. Test voltage all along it til you find a big (2 volt or more) drop. I know it's not easy, but it is the logical next step.

 

[fstncrnrs]

Re: 82 mercruiser 260 pops under load

i will do that next thanks. im assuming its a bad resistor but would that cause the popping

 

[fstncrnrs]

Re: 82 mercruiser 260 pops under load

i went out on water yesterday after checking timing and setting carb with vacuum gauge. popping is still there starts at 2500 rpm. pulled off spark arrester and it didnt look like the back barrells of carb were squirting fuel. but hard to tell because popping thru carb mists the fuel. guess im back to rebuilding carb. does any one no if coil would cause this problem

 

[bigskiohio]

Re: 82 mercruiser 260 pops under load

miss under load += spark plug wires,plugs,weak spark.i am guessing back wot open up till in full throttle

 

[fstncrnrs]

Re: 82 mercruiser 260 pops under load

i have replaced points, plugs, wires, cap,rotor still doesnt help popping. yes pops from 2500 all the way to wot. i have also pulled off throttle linkage to make sure carb opens fully. my max rpm seems to be 3400

 

[Pupek]

Re: 82 mercruiser 260 pops under load

Ever find out what the problem was?

 

[rodbolt]

Re: 82 mercruiser 260 pops under load

popping under a load can also be caused by a water leak at the riser or manifold.
the spak plugs will tell the story if you know how to read the book.
l

 

[fstncrnrs]

Re: 82 mercruiser 260 pops under load

Got tired of chasing problems. Pulled motor. Motor is in process of rebuild but did find I had a valve not seating all the way. I'm goin aftermarket heads good ignition and gona try to find diffrent exhaust set up. I Let everyone no how it turns out

 

[Ohioriver]

Re: 82 mercruiser 260 pops under load

I think you found the problem, I was going to say to check compression, pop thru the carb is a sign of a burnt valve, or a bad head gasket between cylinders.

 

[fstncrnrs]

Re: 82 mercruiser 260 pops under load

tahnks for all your help. replaced motor with 383 aluminum heads and all the bells and wistles. motor is pushing 430 hp. alot for lower unit as it is still an alpha one but its holding together so far. i do have some prop questions but will start a new thread