'91 40hp Merc Classic...No hole shot or plain out

mcdye

Recruit
Joined
Jul 11, 2004
Messages
2
I tackled rebuilding the carbs on the motor. I have worked on car motors quite often so I took the challenge. The problem is that is it got where it would not run out of the hole nor as fast as it should basically not taking full throttle. I got a gasket set and need valve for the rebuild. To my surprise I did not see any trash or gunk I would expect from the oil/gas mix on disassemble. I disassembled both carbs down to the main body and soaked for two hours in carb cleaner. I got it back to together and with fresh gas to do the driveway test and ran fine. It seems to idle to better. The true test showed basically the same results, no hole shot acting half throttle, out of the blue randomly run wide open as it should and acting as it did before. No constant smooth fast throttle. In the mist I would hit the choke and it would not help. I broke down and called a 2 shops, they said it sound like a clogged jet. I find it hard to believe, I found all ports to be open in what I call the jets (brass looking parts with small holes). I plan to get a new fuel filter(I know I probably should have). I would appreciate and any thoughts or direction.<br /><br />Carb Diagram <br /><br />Thanks In Advance<br />CD
 

WillyBWright

Fleet Admiral
Joined
Dec 29, 2003
Messages
8,200
Re: '91 40hp Merc Classic...No hole shot or plain out

Welcome to iboats.<br /><br />Two tests to try with the motor running in the water or on muffs:<br /><br />Put a timing light on each plug lead in turn to see if there is any loss of spark. If the light flashes, the plug is firing.<br /><br />Use a 12v test light (pointy screwdriver-looking thing with a bulb inside and a wire out of it to ground) and slide the point alongside the plug wire into the boot until it sparks there instead of the sparkplug (don't worry, you won't blow the bulb). If the rpms drop significantly, that cylinder is running okay. If drop is slight, there's a problem.
 

rverano

Cadet
Joined
Apr 2, 2003
Messages
26
Re: '91 40hp Merc Classic...No hole shot or plain out

I'm not an expert but I do have a 35hp and 45hp Merc outboard. One thing possibly to check is the throttle linkage. When you push the throttle to full, is the pickup for full throttle pushing the arm that controls throttle as far as it can go. There are a few set screws and stops that control idle and full speed. Sometimes they can become loose and you will not get full speed on your motor. It happened to me.
 

Keith Buchanan

Petty Officer 1st Class
Joined
May 10, 2004
Messages
221
Re: '91 40hp Merc Classic...No hole shot or plain out

Could very well be fuel pump diaphrams, very cheap and easy to do. Worth a shot at $11-00.
 
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