Sputtering Merc

[wippel]

I have a 1987 Mercury 70 hp. When I try to start it it takes significant pumping of the primer bulb and eventually with lots of choke it will run.The motor has recently had a rebuild so I am running double the oil and lots of smoke comes out. I need to give it lots of throttle advance to keep it running in neutral. Once I bring the throttle back to shift it dies out. While it's running on throttle advance it revs fairly high, I'm guessing 2000 rpm, but, I don't have a tach. Even at those revs it coughs every 2 seconds or so. It did run OK a few days ago (still had the tough starting problem) but all of a sudden it sputtered to a hault while running 3/4 throttle and did not start easily after that. The primer bulb does not seem to be as full as other boats I have run. Lots of cooling water is happening. The boat has a built in tank. My first theory is that perhaps the fuel line has a blockage somewhere, but, would that bring about the symptoms I have described? The coughing worries me. Would it be a reasonable next step to try and run the motor off of another tank/gas hose? Sorry for the long post, but, the number of words are a reflection of my frustration with my boat

 

[Hooty]

Re: Sputtering Merc

The coughing sounds like what's refered to as a "lean sneeze".It happens like you described. If woundn't hurt to change to a portable and see if that solves the problem. If that doesn't help, look at the fuel pump and the carbs.<br /><br />c/6<br />Hooty

 

[wippel]

Re: Sputtering Merc

I did try a different tank and the result was the same, although now the primer bulb stayed firm. What I wanted to add is that it belches huge quantities of white smoke when it is running. Especially when it coughs and extra big belch of smoke comes out. It also sounds like a bit of mechanical clunk each time it coughs. Also, I'm thinking that the oil reservoir for the VRO is emptying faster than I would have expected. It went from 3/4 to 1/2 after about 20 minutes of running in neutral. Perhaps the source of my smoke problems. It sounds more like a backfire or cough than a sneeze.

 

[randycc58]

Re: Sputtering Merc

what do the plugs look like? Are they geting oil fouled?

 

[wippel]

Re: Sputtering Merc

Plugs looked good.

 

[fishhunter]

Re: Sputtering Merc

right off ill tell you iam not a tech by no means but every one i know that has a two stroke outboard has disconected that VRO soon as the warranty expired and started mixing thier own cant go wrong that way...if it quits whil u are on a long run somewhere you could toast your motor I expirianced that with my first dirt bike those pumps go out , most have a warining i guess but even if u know it quit it's a long way to troll to the ramp. as for the coughing and sputtering iam not much help but these other guys know thier stuff, "all i know is what i read in the paper" (will rogers sed that) good luck and keep posting

 

[randycc58]

Re: Sputtering Merc

i read right past the part where your you are using twice the oil mixture. try the proper mixture. I would also try seafoam in my carbs and blow them out.

 

[Kenny Bush]

Re: Sputtering Merc

Recheck timing and synchronization. Are your reeds new also? Have carbs been through? And also "I agree about USE THE SEAFOAM". Put it in your gas.