Merc 3.0 idles rough and stalls

Joined
Jun 1, 2003
Messages
6
I've got a 1988 Merc 3.0 (130 hp) that is new to me. I don't beleive the boat has been used much over the last 1-2 years.<br /><br />The boats runs fair when it first gets in the water. Starts easy, but idles a little rough. When I get on the throttle taking off it hesitates a little, but planes out fast and runs WOT 44 mph at 4300 rpm. <br /><br />But, after running awhile it stalls out easily at idle. It then becomes hard to start and stay started, also wants to die when shifting into gear.<br /><br />I've just changed the plugs, which the old ones looked good with no build up. It is idling at 800 rpm. The distributor cap looks good and rotor button looks fairly new. Yesterday I sprayed carb cleaner (1/2 can) trying to see if that would help. The only thing it helped was make the engine more responsive on a fast takeoff, eliminating the hesitation, but it still idles rough and sputters.<br /><br />I'm at a loss as to what to try next. Since it runs so well at full throttle, I figure the problem is not electrical? <br /><br />Any experienced advice out there? :mad:
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,260
Re: Merc 3.0 idles rough and stalls

Time for a Carb kit....<br />You've got to clean out the places you can't get to on the motor with spray........
 
Joined
Jun 1, 2003
Messages
6
Re: Merc 3.0 idles rough and stalls

Thanks for the suggestion. I will try that...next. Here is what I discovered last night.<br /><br />I was inspecting the distributor last night, trying to see if there might be a crack in it. At the same time, I found a crack in the rotor button. Actually, there were 2 cracks in the button and when I touched them a large peice of the button fell off. I am assuming the cracked rotor could have been at least some part of my problem.<br /><br />I'm replacing the button and distributor today..points and condensor also. I was trusting that the previous owner had recently tuned the boat up as he said.
 
Top