Merc15HP Carb problem (I think)

[12Footer]

This one is a long one, but I am totally buffaloed! This engine is a 1988 Merc 15HP. The complaint was great startup, great idle, but very poor operation in gear, with any throttle. It came to me with a classic <br />fuel-starvation problem,which turned out to be debris in the check reeds of the fuel <br />pump(integral to the carb).<br />I removed the carb, ordered the kit (36 bukz!!), and rebuilt it. I re-installed the carb,but found a missplaced timing linkage rod from a previous repair.See, the reason I got this boat to work on was my big mouth. The owner spent 500 dollars thru a wrench,who<br />replaced the coils and trigger. He charged waaay too much, and the engine ran no better than when the owner left it with him.<br />I took the cover off this engine, and noticed the rod thing right off, so I told the owner I would check the guy's werk, and find out why it continued to run poorly underway.<br />So anyhoo, I mounted the carb, cranked the motor thru,and it started first pull, but SMOKE. I mean this thing was kicking thick <br />blue smoke like the choke was on! The idle mixture screw seems to have no effect.This would tell me the choke is stuck closed,but this thing HAS no choke plate,but a "mixing<br />chamber". I'm not sure how this mixing chamber - choke arangement werks. Can anyone describe the thing to me?? The exploded view and associated literature DOES NOT (Clymer manual), and I have no clue. The choke knob has to be removed to get the carb off,and I'm thinking I installed the knob cam or something wrong. Outside of this, I figured the timing was way off, due to the linkage being installed wrong initially, and possably set to compensate. It was off,but not by much, and I brought it into spec.Still won't idle,and too much fuel!<br />I'm about throw a tarp over this thing,and let it sit there for a year or so <br />Any insight would be greatly appreciated,as to what could be wrong,and just how this screwie @#$& choke system operates.<br />It's enough to drive me to drinkin, this merc<br />with the problem of blue smoke stinkin!!<br />

 

[12Footer]

Re: Merc15HP Carb problem (I think)

 

[ODDD1]

Re: Merc15HP Carb problem (I think)

12 footer...check the spring and ball in the bottom of the primer [held in with that 7/16" brass plug on bottom]..the blue primer shaft pushes this ball down when the primer is pushed, it acts like an output check valve...sometimes the ball will push down inside the spring, so the valve stays open all the time and whenever there is vacuum behind the throttle plate it will continue to pull fuel through....and run VERY rich...

 

[12Footer]

Re: Merc15HP Carb problem (I think)

AHA!!!!! ODDD1, you were dead-on!!<br />My blunder. I failed to INSTALL the dern thing! Hence, it was wide arse open,and drawing pure fuel. I didn't notice the thing,and it was still in the old coffee can I used to hold the carb pieces in durring cooking. I just got done removing the carb, and breaking it down..I got as far as the primer cover, and the absense of the ball and spring were obvious. I feel like an idiot now, but would never have even looked for a problem in the primer,had it not been for your heads-up on the thing.<br />Thanks again,ODDD1.