Yamaha 99' Salt series II Stalling at idle

[mrom1234567]

My Yamaha motor seems to idles rough at idle and then stalls. If I give it gas in neutral lock it will run. It also runs fine at higher cruising speed.Where should i start trouble shooting.Can this be a fuel line issue or fuel pump?Can it be an idle adjustment?If so how can i diagnose the problem before I pull the boat.Previously, my primer bulb was not getting hard.However I tighened clams on all hoses, and it seemed to solve the problem.The only out of the ordinary thing I recently noticed is that the problem engine started to idle at a slightly lower RPM. Only about 1 RPM lower though.Please help.Michael

[mrom1234567]

This is a 1999 Saltwater series II Carbed motor.Sorry.Michael

[rodbolt]

test your fuel pumps. a leaking diaphram will do what you describe.also test the spark plug caps for 5K ohms resistance plus or minus 20%.

[mrom1234567]

Stupid question.Can I check the fuel pump or change it without special tools?I am mechanical, but not an expert mechanic.Can it be checked visually? Will it be obvious?Michael

[bigbrownbuku]

when you pull the fuel pump/s from the side of the motor they will split fairly easily with the tap of a screwdriver handle. if you are not comfortable replacing the gaskets and diaphragms you can just change the pump/s wholesale.the spark plug caps unscrew from the ends of the leads.whats the service history on the engine?

[mrom1234567]

The history in unclear.Last year I purchased the boat.I had the water pumps changed and told the Yamaha mechanic to check the motors over.I am usually liberal with what needs to be done.I am perplexed that the Yamaha mechanics wouldn't tell me to change my fuel pumps and rebuild the carbs. I guess their attitude is wait until it fails to replace. Not my motto though.I would repair replace anything for maintenance sake. No matter the cost.This site is a great source of knowledge.I will keep everyone posted as to the outcome.michael

[mrom1234567]

When I put my throttle in neutral lock, and tap it forward to get the motor to idle at 7000 rpm like the other motor, it idles perfect.If I snap it back to the idle position the motor idles at 5 then 4 then stalls.Am I fooling myself to think that I can just adjust the set throttle screw?Should I adjust the throttle cable linkage set screw?If everyone here agrees it is probably the fuel pumps, I will definitely change them.The fuel pumps are probably original to the 1999 motor. How often are these usually changed?Thanks for everyones help in advance.Michael

[mrom1234567]

well, here is the update.My carbs were all gunked up.I had the mechanic rebuild all carbs and change the fuel pumps.(I had to twist his arm to change them-the pumps that is.)The motors run beautifuly now.Michael