'96 225HP Mercury (Low Power)

dustincm1100 · #1 July 23rd, 2008, 07:49 PM

I have a '96 225hp Carbureted Mercury. The motor ran great last year with plenty of power. After it set up over the winter it still idles good and seems to run good throughout the throttle range it just does not have the same power as it used to. With just me in the boat it struggles to get the boat on plane and it can not turn up to its max RPM. I can only get about 4800 out of the motor when it used to turn up to about 5500 last year. Does this sound like a problem with a coil? If so is there a way to check the coils?

CharlieB · #2 July 23rd, 2008, 09:16 PM

First thing to do is pull the spark plugs and take a careful look at the color, any light color may indicate the carbs are dirty and running a bit lean, potentially dangerous, as that could lead to melted pistons.

Second, get an adjustable gap spark tester, set it the 7/16 inch gap and test spark on all cyl's. Hot bright blue arc required.

It is still possible to have a weak high speed winding in the stator coil, you will need a DVA meter to test the stator output.

dustincm1100 · #3 July 24th, 2008, 09:34 AM

I appreciate the quick reply. I will check my plugs and check the spark and let you know what I find.

dustincm1100 · #4 July 25th, 2008, 08:37 AM

Ok I have a new found a new sympton on my motor. I used a spark tester and noticed that all but 1 cylinder was sparking good. If I am facing the back of the motor the starboard middle coil was not firing at all. So before I went and bought a new coil I decided to switch that coil with one that was definitely working and it wouldn't spark either when plugged into that plug. What could be causing that???

dustincm1100 · #5 July 25th, 2008, 05:59 PM

My coils have a four wire plug connecting into them. Is there any way I can check these wires and try to figure out what my problem is?

CharlieB · #6 July 25th, 2008, 08:06 PM

Rapair/CDI Ignition Troubleshooting Guide will walk you through all the tests.

You will need that DVA Meter to be sure of correct readings or a DVA adaptor for a good VOM.

You already tried that coil in another position and it works?

And you only have a problem on 1 cyl, chances are the guide /tests will find a bad stator, but NO RETURN blah blah blah, you must MAKE SURE, stators aren't cheap.