88 Johnson 150 cutting out

Heres what Ive noticed and done so far. The motor is a 1988 Johnson w/a 98 powerhead w/630 hrs. It starts fine, idles fine, and runs good except for every once and a while it coughs. It started this spring at a cough per trip, no big deal. Some days I run it and theres no coughs, but lately it seems to be getting worse. Ive done the fuel water sep 3 times and theres no water in it. Ive checked the vent line, its routed fine no low spots. The plugs have been done twice, they all look the same, good color. I run 2+4 cond in every tank as well as carbon guard following the rec dosage. I'm confident that the fuel source is very good.<br /><br />Tommorrow am I'm going to do a compression test, whats the safest "right way" to do it? Ive been told to warm the motor, remove the six plugs, open the throttle wide and then turn 8 cranks on the starter for each cylinder. Question? How do I disable the powerpacks so that no sparks come from the coilsor is that neccessary?<br /><br />Anybody have an educated guess as to my probs? <br /><br />Its really killing me not to be able to fish this weekend and I appreciate any help, Thanks B

Re: 88 Johnson 150 cutting out

Your compression test procedure is OK. Post the results.<br /><br />When is the last time that you cleaned & overhauled the carbs?

Re: 88 Johnson 150 cutting out

SoLittle, Thanks for that, The carbs have not been rebuilt for the last 4 years Ive had the boat, and maybe more. It did get a new powerhead in 98, that might be the last time. This year I have done the fuel line from the wat/sep to the motor, the fuel filter (that was clean) to the pump. The pump does look old, as do the coils and motor.<br /><br />Ok, heres the results, port side top to bot, 89, 88 86, stbd side top to bot, 96,97,96. Is that a very bad sign or what? Its all near the 10% area, but, why so close on each side, and not balanced?? <br /><br />I found another problem. After the test my motor would not trim back down. I taped the trim down button and went back to the motor to start wiggling the wiring harness. On the stbd side theres a plastic junction bar for wires. When I wiggled it the motor started trimming down. I found that 2 red wires that connect together, the screw was almost falling out. I cleaned the 2 connecters, applied dielectric grease and screwed them tight, and checked the rest.<br /><br />She ran much better today, no coughing in the wake zone, no sputtering, so I decided to put her to the test. I trolled at 1200 for an hour and not one cough, I thought I was all set. Nope. When the rain came down I pulled the lines in and headed for "the barn". She would not go. Just bla, ba ba ba, ba ba ba. I shifted to nuetral and went to high idle, it reved right up to 2500 and burned off some smoke, I put it in gear and it ran great back to the slip. <br /><br />One other thing I should mention is that I gapped the plugs to .32 They recommend .40 (but it seemed to run better at .32) Should I gap them at .40 ? What makes a hotter spark a wider or narrower gap?<br /><br />Thanks for the help, again, B