Is this normal?

[jiffyboat]

OK I have a a 1997 Mercury 75HP two stroke the 75ELPTO , the motor have 120psi compression, it fires right up, and I can say that it runs fine at idle, ....carburetors and fuel pump just rebuild, new plugs, clean fresh fuel , but the motor sounds under accelerations like if a cylinder is no firing, or low spark, but after doing the the finger test ,no recommended to persons with a bad heart, there is spark, I also took the tests light and pinching the boots, in other words shorting to ground the cylinders, two and three the motor basically won't react at all, but when pinching the N1 it dies right away...I haven't try the boat in the water , so I can't say if it runs fine or not in the river.. any suggestion.. thanks

 

[RogersJetboat454]

Re: Is this normal?

OK I have a a 1997 Mercury 75HP two stroke the 75ELPTO , the motor have 120psi compression, it fires right up, and I can say that it runs fine at idle, ....carburetors and fuel pump just rebuild, new plugs, clean fresh fuel , but the motor sounds under accelerations like if a cylinder is no firing, or low spark, but after doing the the finger test ,no recommended to persons with a bad heart, there is spark, I also took the tests light and pinching the boots, in other words shorting to ground the cylinders, two and three the motor basically won't react at all, but when pinching the N1 it dies right away...I haven't try the boat in the water , so I can't say if it runs fine or not in the river.. any suggestion.. thanks

Unless you can adjust your fingers to have the ignition jump a 7/16"-1/2" gap, I would be getting a real spark checker (one that can measure spark gap) at an auto parts store. All the finger check did was tell you there is spark, not if it's sufficient.

Have you checked compression?
Did you synchronized the carburetors correctly?

 

[jerryjerry05]

Re: Is this normal?

Get one of these.$6 almost anywhere auto parts are sold.
7/16 inch.

 

[jiffyboat]

Re: Is this normal?

thanks for all the info, I will definitely buy one of those spark tester... I found , that after rebuild the carbs, forgot the put back the air fuel mix needle, found that when I went to the water for a test and ready to do the final carb adjustment ... and ups, no needle, blocked the hole with my finger... lol I love my finger, and them the motor started running better, even I was able to take a ride test , of course had to remove the finger out the hole, and the motor runs great and fast.at high speed.. went back home and found the needle, back in the carb and problem solved... thanks any way for the advices , they always help