04 Merc 60/40 2 stroke carb misfire?
I got a problem with my outboard. I have a 2004 Merc, 2 Stroke, Carb, Elect Start, 60/40 Jet. It usualy runs just nice. Untill this season. I have always done all the usual maintance/storage pratices.
So let me explain whats up.
1st I got the boat uncovered, installed some FRESH fuel/plugs and ran the engine at the house before heading to the lake for the yearly test & tune. Started up fine as usual. Sounded good. Not misfiring, hand over exhaust felt good. Idled great etc.
Took boat to lake. Running good. Taking my time letting her warm up and what not. Sounding good. Now at 2800 rpm and all is well.
Started to bring the RPM up to get her on step and have a little fun. Hit aprox 4000 rpm and somethings not right sounding almost like the jet was pluged up and cavitating. I shut her down and was totaly expecting to find something at the jet. Nothing there looks good and clear. Try it again and same thing. So I look everything over and all looks good. I dont see anything unusal. I replace plugs again. Checked jet impellor clearance. Anything I could think of while out on the lake. I ran the engine to get more of a feel for the problem. I have concluded that at around 3800 RPM is when the problem shows up. Egnine seems like it has a miss. At around 4000/4200 it sounds really bad. 5000 RPM sounds bad to the point that I dont even like running it like that. At any RPM 3800 or higher the problem is always there. I can not get he boat to get on step at all. It just totaly runs bad and boggs down.
Now in reverse I can only get about 2800/3000 RPM at full reverse. But when in full reverse power it "pulls" good. No engine miss.
I am an automotive tech by trade but 2 strokes and marine ignition systems are a little diferent. I have a few ideas for testing ie: using my ignition scope on it. But to do so I would have to have the boat in the water and I dont like the idea of my 9k scope that close to water lol. If it got wet I would not beable to fix cars for a month or longer lol. I DO have the merc service manual so I can run through some tests that are in the book. But I am asking if anyone might know what direction to head towards. Or if one might even know if something like a CDM is common enough to "shot gun" a new one in and see what happens.
I am on a budget due to my wife not working beacuse of a baby on the way or else I would just take it in to be fixed as I am so straped for time these days.
Ok so if you are a marine tech or have enough exp to give some good ideas please respond.
Thanks very much in advance!