Motor running rough

mercdaddie

Recruit
Joined
Apr 6, 2005
Messages
4
Hi i am new to the whole outboard machanics thing, also new to the forum, i have a 1974 Mercury 650 thunderbold, 3 cyl. It will crank with the first key turn very easily, and idle ok for about 30 seconds and will seem to hicup and die down some times quiting and others it will jump back up to idle speed, when i try to give it any power sometimes it will rev others it will just die, almost like choking out, i thought it might have had some thing to do with the vent being closed, but i opened it the next day and tried it again. same thing, i am thinking it may be a fuel pump problem, i have a new gas tank so its not the vent, when i pump the primer bulb till it gets hard gas drips out of the carbs(2 carbs), i checked the spark plugs and they seem to have a bit of oil on them but it still idles fine, also the cracker i bought the motor from left a bold out of the head where the spark plugs are located and water was coming out, i fixed that thinking that water was getting in the cylinders but this still didnt fix my problem, sorry about the long post, but i have one more thing, it seems this outboard may have had a power tilt/trim sys. on it b/c it doesnt have a reverse locking mechanism on it, i have a safety chain rig up in there for now, but does any body have any other suggestions? i have a 1971 4 cyl merc same hp, with the reverse lock on it, how hard would a swap be?<br /><br />once again sorry for such a long post, any help would be appreciated, plan on doing a fuel pump gasket replacment soon, any one know the part number for the fuel pump gaskets and the carb rebuilt kit or gasket kit? the fuel pump looks kinda like a triangle type shape,<br /><br />thanks again guys<br />mercdaddie
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: Motor running rough

Your lean on idle, maybe adjustment, might be dirty carbs, the locking system off a 4 cyl. won't work, you need one off a mid sized center section, Do not chain it down if you hit something it would damage the transom--Bob
 

mercdaddie

Recruit
Joined
Apr 6, 2005
Messages
4
Re: Motor running rough

so do you think this could be a fuel pump problem at all then, and what about the missing screw from the block where the spark plugs are?, the chain is pretty loose on the reverse would it be better to put a rubber bungy on it? also how would i adjust the carbs to get a richer mix would i do one at a time or adjust a little on both as i work to a richer mixture?
 

mercdaddie

Recruit
Joined
Apr 6, 2005
Messages
4
Re: Motor running rough

I checked the fuel pump and adjusted the carbs abit, didnt amount to much, i am going to replace the fuel pump gaskets and go from there, any ideas are welcome
 

mercdaddie

Recruit
Joined
Apr 6, 2005
Messages
4
Re: Motor running rough

Well the fuel pump gaskets have been changed and she idles a lot better but when i put it in gear and give it gas it will only go up a few rmps and stay there no matter how far i push the trottle down. whats causing this, i tried to make the mix abit richer but this doesnt help much... any ideas? the carbs have been cleaned. and the compression is 141, 147, 144 top to bottom, also i am getting the leaky carb syndrome when i pump the primer bubble... help this is frustrating
 
Top