mercruiser 190 carb

[Century riviera]

Hi all. I have a mercruiser 190 that is having carb issues. The carb has the Sierra tag 18-7619-1. According to the Sierra book it's the right carb for this motor but when the 4 barrels open up at wot the motor sounds like its running out of fuel for only a half second or so and then picks up again. Kinda the opposite of surging. I have rebuilt the carb, added electric fuel pump, fuel/water seperator, electronic ignition, new plugs wires cap rotor. Even fixed all the other 3.7l problems. Including all new gaskets.
not sure if the carb is jetted properly, or how I could tell.
thanks for any ideas

 

[Scott Danforth]

welcome aboard.

did you check fuel pressure between the carb and pump? should be between 3 and 7 psi.

when you did the pump, did you set the float level properly?

 

[Century riviera]

Thanks for the info. I set the float to spec according to the sheet that came with the rebuild kit. Also did the needle and seat. Motor runs awesome even when the 4barrels start to open. Only acts up at fully pinned. Pulling back just a little it goes away.

 

[kenny nunez]

The bog you are describing may be the secondary air valve opening too quickly. When it opens too fast you lose the air velocity. There is a small spring that controls the speed that the valve opens and it can be adjusted. If you still have the instruction sheet from the rebuild kit the adjustment is described. You may have to experiment some to get the "sweet spot" where it will not bog.

 

[Century riviera]

Update on the carb issue. Took it apart and double checked all the measurements. Even used a dial indicator!. On the water nothing much has changed, wot it still has a miss. Pulling back on the throttle just a bit it goes away. Phone gps says 42 mph and digital timing light reads 4080 rpm. Motor is rated for 4800. Could this be part of the problem?

 

[2fishy4u]

I had this issue last year, mine would bog at 80% throttle and be fine if I backed off or gave it more throttle. It was fine after adjusting the secondary's like Kenny suggested. Although it took a bit to get it right.

 

[Century riviera]

Update to my last post. When I replaced my mechanical fuel pump with electric, I mounted the pump at the back of the boat next to the fuel water seperator. Seemed like a good spot. What I failed to realize is electric pumps are pushers not suckers. Moved the pump to the front beside the fuel tank. Made a world of a difference. Sometimes it's easy to overlook the obvious.