I have started a new thread in hopes of attracting some fresh ideas about a stale problem. This has baffled me since early August, but with a lot of advice from this forum, I?ve been able to eliminate a lot of possibilities; however, the solution is still a mystery. For more background info, read the thread titled ?1988 Mercury 100 hp w/ acceleration problems?.
The motor: This is a 100 h.p. motor w/ a 2+2 system. The top two carbs get fuel at idle and the bottom two get enough to keep the pistons lubed but not enough to fire. At increased throttle, all 4 carbs contribute.
The problem: When the boat is on the water and I am at WOT, my motor is functioning at about 50%. It will not even get on plane. The situation improves when I squeeze the primer ball. I can squeeze until my hand cramps up and I get about 90% out of the motor but when I stop squeezing, the motor returns to a dog.
Suggested solutions: In a moment of defeat I took the motor to a mechanic who looked at it and said I needed a new stator. (I?m not sure he actually did any tests). Because the performance of the motor improved when I squeeze the primer ball, I?m reluctant to believe that I have an electrical problem.
With guidance from this forum, I have ruled out many fuel supply problems. Results of various fuel pressure and vacuum tests are w/in the specs listed in my shop manual leading me to believe my fuel lines and fuel pump are OK. The carb bowls are getting fuel, I?m just not sure if fuel is getting into the cylinder.
I replaced the accelerator pump that is supposed to give the 3rd and 4th cyls a ?squirt? of fuel when the throttle lever depresses the accel pump. This did not resolve the problem. I just removed and dipped the carbs in cleaning solution but have not had a chance to see if that helped. Sounds good in the driveway w/ muffs but no way to tell if bottom two carbs are contributing until I get it on the lake.
What?s next: Is there anything specific to this 2+2 system that I should look for. Besides contributing the ?squirt?, does anyone know how the accelerator pump contributes to the motor output at high throttle? A fuel line branches off the main line between the 2nd and 3rd carb and leads to the accell pump. Another line leaves the accell pump and goes to the back of the motor. Looks like it is using bleeder lines? Could I have a problem there?
Thanks to all who have contributed to the other thread and thanks in advance to new contributors who may have fresh ideas to this stale problem.
The motor: This is a 100 h.p. motor w/ a 2+2 system. The top two carbs get fuel at idle and the bottom two get enough to keep the pistons lubed but not enough to fire. At increased throttle, all 4 carbs contribute.
The problem: When the boat is on the water and I am at WOT, my motor is functioning at about 50%. It will not even get on plane. The situation improves when I squeeze the primer ball. I can squeeze until my hand cramps up and I get about 90% out of the motor but when I stop squeezing, the motor returns to a dog.
Suggested solutions: In a moment of defeat I took the motor to a mechanic who looked at it and said I needed a new stator. (I?m not sure he actually did any tests). Because the performance of the motor improved when I squeeze the primer ball, I?m reluctant to believe that I have an electrical problem.
With guidance from this forum, I have ruled out many fuel supply problems. Results of various fuel pressure and vacuum tests are w/in the specs listed in my shop manual leading me to believe my fuel lines and fuel pump are OK. The carb bowls are getting fuel, I?m just not sure if fuel is getting into the cylinder.
I replaced the accelerator pump that is supposed to give the 3rd and 4th cyls a ?squirt? of fuel when the throttle lever depresses the accel pump. This did not resolve the problem. I just removed and dipped the carbs in cleaning solution but have not had a chance to see if that helped. Sounds good in the driveway w/ muffs but no way to tell if bottom two carbs are contributing until I get it on the lake.
What?s next: Is there anything specific to this 2+2 system that I should look for. Besides contributing the ?squirt?, does anyone know how the accelerator pump contributes to the motor output at high throttle? A fuel line branches off the main line between the 2nd and 3rd carb and leads to the accell pump. Another line leaves the accell pump and goes to the back of the motor. Looks like it is using bleeder lines? Could I have a problem there?
Thanks to all who have contributed to the other thread and thanks in advance to new contributors who may have fresh ideas to this stale problem.
