I have a 2000 23hp vanguard that is missing under aload. The motor idles great and runs great when not under aload. As soon as you put aload on it (put it in the water) it starts missing.
The motors compression is 150 on the left side and 170 on the right which I thought was ok. When turning over both sides have fire.
Now the side that has 150 (left side) after running under aload it is cool to the touch which tells me it is not working. I tried to pull the plug wire off to see if it was still firing and it shocked the crap out of me. I killed the motor pulled the plug and it is wet, I'm confused.
I feel like this is a ignition problem but not sure how the ignition system works on these motors yet. Is there like a high speed coil?
I'm also thinking it could be maybe a stuck valve, or broken spring. I'm just not sure. (I have not had a chance to pull the valve cover)
I would like to know how the ignition system works. And what some of you are thinking. Any info you have would be great.

Did ya try new plugs?

Yes I have.

I just bought this motor. And I replaced all the fuel line componets from the gas tank, hose, bulb,fillter,and fuel pump. And replaced the plugs. Changed out the old gas. I do not think it is a fuel problem I just trying to let you know what I have done already.
I'm kind of thinking that the coil is not putting out enough spark while under the load. because the motor runs great any other time as long as there is no load. Coil????

May be the diode in that wire going from one coil to the other that is out.

Is a rev limiter involved?

Nevermind, Thought you may have disconnected the governor and added a rev limiter. One time mine went out and another time a wire broke going to it and I had similar symptoms.

No, swamp it stock as for as I can tell, no addons.
But I do think it is going to be a coil, so I'm going to switch sides with the coils and see if the dead hole moves. I think that will be the easiest thing to try.
I was kind of hoping that someone would be able to tell me the way the ignition system works on these motors before I jump in to it this weekend. I'm sure I will figure it out, I would just like have a little more understanding of the system. Is it an electronic, or do they have point, Just any thing that would help narrow my serch.
And thanks to everyone who has commented, I appricate all your help.
And please if you have anything else let me hear it.

Well She is running like a top. I decide just to crank it and let in run about half throttle on the trailer no load just to re check myself before I started tearing things down. And I noticed the side I thought was running good was running lean. So pulled carb, cleaned things out found some crap in one of the jets, put it back together, and bamm runs like a champ.
I guess I was not running it long enough to let the cylinder I thought was bad get hot and the side that was lean was just getting hot alot faster. Anyway thanks to all that helped.
Now put on my new prop and we are off.