mercruiser 140 cam

[ebear]

I need some second opinions,
I have a 1986 3.0 140hp It' had been sitting for a few years and had been started aprox bimonthly durring that time.One time the motor had stuck but not badly. finally the hull was finished and 3 weeks ago I took it out.first day was flawless,the second day was fine exept it backfired(hiccuped)only once at about 3400 rpm still ran fine and quiet. 3rd and 4th time out, no problems. Last time out, we were returning from a 20 mile run keeping at 3000, untill the last 2 miles, brang the rpm to 3500, after aprox 4 minutes it backfired once more. apon slowing to no wake speed I noticed what sounded like a lifter tap. Now I have removed the valve cover and side plate looked at the lifters , rockers and cam. All look fine. the noise appears to be coming from the cam gear cover. the noise seems more like a rythmic metallic chugging than a tap. by the way there is very very little metal in the oil or the filter ( I tore it apart and put a magnet to it)
Now the question is. Is it possable that the cam gear has broken a tooth and if so, would it have caused or been a result of the backfires Or am I on the wrong road and you have a different idea

thanks

 

[Bondo]

Re: mercruiser 140 cam

If a Cam Gear shears a Tooth,....... The motor just Won't run.....

I wonder if the tapping is coming from the Fuel Pump,......

A Lean condition will cause Hiccups.......

 

[whywhyzed]

Re: mercruiser 140 cam

I think the cam gear is fiber and not metal (every 3.0 I've seen apart had fiber gears) - if there's metal in the oil, it might be the something else in the front end....maybe one of the cam retaining bolts is backing out and the cam is hitting it

 

[ebear]

Re: mercruiser 140 cam

That may be. It's definatly metal on metal but not a tap. I'll first check the fuel pump , if thats fine I'll remove the cam cover
thanks guys I'll let you know