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1988 100hp Mercury/Mariner

W

wam

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It's actually got the SeaRay logo on the cowling, on a 16' SeaRay Seville, but it's a Mercury/Mariner! Anyway, it has been, and still is, a very good engine, but what I've been living with for the past 2 years, is a really rough idle. When I put it in gear, and anything above 2000RPM's, she is really a strong engine. But when I put it back in neutral, to pick up the skier, or pull up to the dock, it is really rough, sputtering, and eventually, will die. I am somewhat familiar with the fact that at idle, this 4 cylinder engine runs on only 2 carbs, and I'm curious if anyone out ther has had a similiar experience, and if it is advised to take the top two carbs off, soak them in carb cleaner, and clean them up really good? Or, is there another less invasive fix to getting the idle smoothed out on these engines? As mentioned, when I give it WOT, or even anything above 2K rpm's, she runs like an outboard motor should, so I don't want to make the matters any worse! Thanks for any advice or experienced information on this...
Wayne
 
there is no magic cure in a bottle, fix it right. Check and see if a carb is flodding by pumping the bulb and looking through each carb with a flash light. Any drips are bad....jb
 
If the #3 and #4 plug wires are pulled off does it get better? If yes, than those cylinders are pulling gas it idle. Probably a fuel pump diaphragm or accelerator pump nozzle leak.

If no, than reset all the carb linkage by the book. Loosen and tighten all the screws on the vertical tie bar so all the shutters are shut.
 
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For sure, want to do it right, and I agree it won't come out of a can!

Just so I'm clear on the two recommendations:

1. You want me to squeeze the primer bulb while the engine is running, to see if gas is leaking out of any carb, or squeeze the build when the engine is not running to see if gas is leaking?

2. Should I start the engine with the #3 and #4 plugs attached, and then pull plugs, or attempt to start it with them removed?

Another tidbit of info, is when I'm in idle after the engine has warmed up, on occasion, I can push the ignition key in (choke), and it does seem to make it idle better, but not for long.

Thanks for the feedback so far.
Wayne
 
wam said:
It's actually got the SeaRay logo on the cowling, on a 16' SeaRay Seville, but it's a Mercury/Mariner! Anyway, it has been, and still is, a very good engine, but what I've been living with for the past 2 years, is a really rough idle. When I put it in gear, and anything above 2000RPM's, she is really a strong engine. But when I put it back in neutral, to pick up the skier, or pull up to the dock, it is really rough, sputtering, and eventually, will die. I am somewhat familiar with the fact that at idle, this 4 cylinder engine runs on only 2 carbs, and I'm curious if anyone out ther has had a similiar experience, and if it is advised to take the top two carbs off, soak them in carb cleaner, and clean them up really good? Or, is there another less invasive fix to getting the idle smoothed out on these engines? As mentioned, when I give it WOT, or even anything above 2K rpm's, she runs like an outboard motor should, so I don't want to make the matters any worse! Thanks for any advice or experienced information on this...
Wayne
Click to expand...
Your post was 13 years ago. Do you still have the same motor? I have a '89 model that is having a bad cough, but typically runs like a champ. Which are the 2 cylinders that run below 2000rpm? Top 2 or bottom 2, or some other combo?
 
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