90's merc 40hp 4cyl 2 carb question

[bassforme]

when at idle on muffs what results should i get when placing my hand over top carb? and on the bottom carb? trying to figure out why I have good idle at home muffs or barrel but hard to get her to run at the lake.when on the lake I have to tilt the motor up to start and then lower motor and good to go until I stop to fish then repeat to get going again. things I done,soaked carbs in berrymans,checked compression 120 on 3 and 119 on the 4th,rebuilt fuel pump and replaced fuel lines..thanks for any info

 

[faztbullet]

Check spark. Had a customer with a 50(same motor) had close to same problem. The backpressure would cause the RPM to be lower and the spark was weak(would not fire under compression). Ran and started fine in barrel. Result was stator bad.

 

[racerone]

Checked exhaust tuner for blockage ?

 

[bassforme]

Where can I get a spark checker and is there a setting? And where is the exhaust tuner on my motor...thanks