1983 Mercury 18hp runs rough, no power

[kwebb]

Mercury 18hp. The motor was given to me, I have know idea how long it has sat. started it and seemed to run a little rough. Thought if I took it out on the lake, maybe it would de-gunk the carb on its own. after running it for a few hours it still ran rough. tore down the carb and was supprised at how clean it was. Ran brushes and cleaner through all the holes, and put a new gasket kit in it (kit # 1399-8154). Adjusted the jet to 1 and 1/2 turn out, started it up and it still runs rough, and does not sound like it revs all the way up. it sounds like it is running with the choke on, heavy smoke out the exhaust and some black oily discharge. the bulb is firm when it is running, and if I pump it, that does not seem to help. both cylinders check out at 125 psi. spark plugs were black and suity. could the timing be off...I do have a timing gun, but have no idea how to check this motor or where it should be. I am also going to get new plugs tomorrow.

Any ideas to point me in

Engine SN: 6268345
Carb #: 222 BC2D 8704

Thanks

kw


Is it true that this motor is exactly the same as the 25 Hp except for the carb?

 

[shimano]

Re: 1983 Mercury 18hp runs rough, no power

I'de definitely try new plugs and check the spark on both.The choke is also a primer maybe its not working properly.Also check that the throttle is open all the way.There is more of a difference than just the carb to make it a 25 ,The exhaust is tuned different.As far as he timing goes,I'de get a shop manual.

 

[kwebb]

Re: 1983 Mercury 18hp runs rough, no power

put new plugs in today, and it still ran like its flooded. so with the throttle all the way up, I kinked the gas line going to the carb. 30 seconds later, it reved real high for about 3 seconds, then died from lack of gas...I think I'll check the float adjustment. when I tore down the carb, the little rubber tip on the end of the needle valve looked good, so that is why Im thinking the float adjustment. this motor does have an electric start and choke on it, but the choke plunger seems to be working properly. it springs up when not held down, and when it is held down while the motor is running it will flood it.

These are just my bright ideas, if any one else has any others, let me know

kw

 

[Mi duckdown]

Re: 1983 Mercury 18hp runs rough, no power

There are diaphrams in the enricher/choke, asm. that maybe bad. It is about a 15 bucks for the rebuid kit. the plunger going down than up, only means the spring is good.

 

[kwebb]

Re: 1983 Mercury 18hp runs rough, no power

Adjusted the float...didnt help. Mi I think you may be correct, something with the choke. I tried adjusting the jet, and it did not seem to matter weather it was turned in all the way or 1 and 1/2 turns out. there was piece to the gasket set that I did not recoginize. a little rubber O ring. when I took apart the choke plunger, I looked to see if it went in there but it did not look like it should. there was a small fiber washer that did go in there, but I did not see any parts on the end of that plunger that looked like they were replacable. I will take apart the choke plunger again and look at it some more

 

[kwebb]

Re: 1983 Mercury 18hp runs rough, no power



#19 is the O ring I had left over, replaced that, and the carb is assembled as it shows in the diagram. with a new Diaphragm and gasket set.

Still floods...this thing is kicking my butt. what am I missing?

 

[Mi duckdown]

Re: 1983 Mercury 18hp runs rough, no power

Sorry. i meant fuel pump when refereing to diaphrams. but the kit for both comes in the same package if you order it correctly.
Again sorry. brain going faster than my typing.