89 mercruiser 3.0 pops like popcorn?

[peeper]

im new at this and not sure if im doing this right but i have a 89 maxum that has a mercruiser 3.0 and a alpha one drive. i just replaced the old points style distributer with the delco voyager electronic distributer and after reading this sites threads i had it running great thanks to you guys but after a few hours of running i was at 4200 rpms then it just kinda fell on its face and started making a constant popping sound from the carb. It wont idle very long, it starts back up but you have to pump the accelerator and crank it then hurry up and put it in gear, thats how i limped it back to the dock. the boat has new plugs, wires, dist. cap, rotor button. i took the flame arrestor off to see if there was soot in it but it looked normal any help would be greatly appreciated.

 

[Fordiesel69]

Re: 89 mercruiser 3.0 pops like popcorn?

A few hrs at 4200rpms would indeed cause the problems you describe. Do a compression test.

 

[peeper]

Re: 89 mercruiser 3.0 pops like popcorn?

thanks ford diesel but i worded the post wrong, most of the day i was floating and cruising, cruising at or around 3000 rpm and here and there at wot but not for more then few minutes at a time and when it started acting up i had been been at 4200 for probably around 15 minutes or so, not long

 

[Buck Horn Deer Farm]

Re: 89 mercruiser 3.0 pops like popcorn?

You may have a cam problem. worn off cam lobes will cause it to pop.

 

[peeper]

Re: 89 mercruiser 3.0 pops like popcorn?

i really appreciate the help guys, im gonna start checking it out, i should probably add that it went from hero to zero all of a sudden

 

[Fordiesel69]

Re: 89 mercruiser 3.0 pops like popcorn?

I know this sounds like a PITA, but could you post a video on youtube. For us to see it would help in troublshooting. You could have internal engine issue, a failed ign system component, or carb issue. Maybe even as far as a leaky intake gasket like on the 120HP I did last week.

 

[Ryan50]

Re: 89 mercruiser 3.0 pops like popcorn?

I just had this exact problem. Turned out the rocker arm on the number 3 intake valve had come off the valve and pushrod. I reinstalled and adjusted all valves and engine is back to normal. Do a compression test and lets go from there.

 

[tonk62]

Re: 89 mercruiser 3.0 pops like popcorn?

do you have a temp gauge? Its not overheating, is it?

 

[peeper]

Re: 89 mercruiser 3.0 pops like popcorn?

hey guys just got done working my boat, the problem was as ryan stated, i had a valve problem. the previous owner had the valves to tight and when i finally got the boat running right where i could run higher rpm the rocker arm on #2 cylinder broke into and pulled the stud up a bit, now im not a novice mechanic but figured i would run the nut down on it a bit and tap it back in and thats what i did but dunno how long it will hold, any suggestions and where can i find rocker arms for the boat at?

 

[fishrdan]

Re: 89 mercruiser 3.0 pops like popcorn?

Rocker arms are one of the few parts that you can buy the automotive equivalent, much cheaper than the marine version. I bought a full set when I rebuilt my 140HP and they were around $3/each. Rockers for a 68 ChevyII with a 153CI 4 cyl engine will work, they are 1.75-1 if I remember correctly, certainly not the standard small block GM 1.5-1 ratio.

For the stud pulling, that's not good as it could do it again. An ol' school racer trick is to pin the rocker studs. Drill a small 1/8" hole down near the bottom of the rocker pedestal, so it hits the and goes most of the way through the stud, then drive a roll pin into the hole so it locks the stud into place. Look it up on google or youtube so you can see how it's done, you don't want to go too high as it could weaken the pedistal. You could also clean up the stud and pedistal hole really well, then use red locktite to keep the stud in place, should work. I wouldn't do the roll pin with the head on the engine since you don't want metal shards going into the engine.

 

[Fordiesel69]

Re: 89 mercruiser 3.0 pops like popcorn?

Just drill + tap and use an allen set screw on the side AFTER you set the valve lash. Or retap the existing hole and use a repair sleeve.

If rockers from an L6 would work, I have some spares.