Need Help

Hello everyone I hope someone can help.I have a 1995 mercury black max 200 2.5.This motor was giveing me problems with three dead cylinders with no spark.After a few checks I came across that the switch box or power pack was defective.After replaceing that unit every thing went back to normal spark on all 6 cylinder.Well here is my problem my motor seems to be bogging when wot rpms stay at around 2000.My boat has two motors when I use the other motor it helps the motor that is bogging get up to higher rpms and run better once the boat is going with the help of the other motor I can run the bad motor up to 5500 rpms.Here is what I have checked compression is at 125 on all cylinders spark is good on all cylinders fuel seperator is clean carbs are clean fule pump is also good also tryed decarb.I also forgot to metion that I had a bad voltage regulator that I also replaced.While the motor does this condition I tryed pumping the prymer bulb and tryed chokeing the motor with no diffrence then that the motor trys to shutt off from chokeing it.If anyone has any idea of anything I might be missing or someone that has had similar probelms can help it would be great.Thanks to all.

Re: Need Help

There are lots of possibilities and I would not guess at the most likely cause(s). If my motor had these symptoms, I would first try to determine if it is a fuel related or ignition related problem. I realize that the "choke test" you did probably indicates that fuel starvation is not the problem but I believe that the procedures described in the following Mercury Service Advisory are more definitive in eliminating fuel starvation as a cause.

http://www.marinepartsman.com/Mercury-Marine-service-bulletins/Mercury-Mariner/2001/EN_17.PDF


The next test I would do is to monitor ignition system voltage with test equipment while the motor is bogging. You did state that you confirmed that "spark is good on all cylinders" but you did not explain how you confirmed this or if it was checked while the motor is bogging. For example, using a DVA meter (to check primary voltage) or a SmarTach (to check secondary voltage) while the motor is bogging is more definitive than watching for a spark while the motor is idling or being turned over with the starter. Also, sometimes the voltage can be below spec and cause the engine to bog and still be high enough to cause a spark to be visible.

These are my suggestions. Others on this forum may have additional or better suggestions.