Hello all! I just signed up today, hoping to find some help with my engine problem.

[AndreyCat]

I bought this 1996 StingRay 586 with a cracked block, put new engine in it, only things left old were the ignition system, manifolds and carburetor. This is what happens: It will run perfect for 15 - 20 minutes, then it will start hunting, rpms will fluctuate from 2700 to 3200, like its running out of fuel, it has a new fuel pump, and carb has been disassembled and cleaned and assembled with new everything in it, all the adjustments were done as the Clymer manual specifies. I have removed de anti syphon valve from fuel tank and made sure the pick up tube was clean. Is there any possible way that this could be an ignition problem?

 

[thumpar]

First thing to do is lose the Clymer manual. You can find a link to a Merc manual in the adults only thread. You should try running it on a remote tank. Also what engine are we talking about? Serial number would really help.

 

[AndreyCat]

I am sorry, forgot the engine!! it is a mercruiser 4.3lhx, weber 4bbl carb

 

[alldodge]

In most cases of hunting its almost always the carb. An incorrect float setting, metering rod. Do you still have the weber carb?

 

[AndreyCat]

Yes the weber is on it now

 

[AndreyCat]

how do I get to the manuals? or to the adult only thread?

 

[alldodge]

There is a lot of info and links in the Adults Only section which is at the top of this section your posting in. There is also a link in my signature listing "Adults Only"

Since you ran the motor without an antisiphone valve this would not be the issue. The motor starts this after 15-20 so it may be a vacuum issue on the tank. If it only happens when the motor is warm then I would guess its the carb. The carb just may not be adjusted correctly. the weber carb is a good carb and works well if adjusted correctly.

The fuel pump was replaced but would still be real good to know if the pressure is between 4-7 psi and all rpms

 

[AndreyCat]

AllDodge, I will do those checks tomorrow, I actually have a copy of the original weber carburetor service manual, the adjusting procedures on the weber manual and the Clymer are the same. What happens in the carb when the floats are not adjusted correctly? will they just keep the fuel flow restricted? I did not read anything on how to adjust the metering rods.....

 

[alldodge]

Most cases is the idle circuits are not cleaned out. Yours being in the 27 to 3200 rpm range this would be the main as well as the idle circuits. The 15 to 20 minutes should be about the time the choke opens. If choke is already open prior then look for other things which can cause a lean fuel mixture. So not knowing anymore about the issues I would look at the cleanliness of the channels, metering rods and choke setting

 

[AndreyCat]

Ok, thank you much for your advise, engine running like it should, for future reference the anti syphon valve was the problem.