muchco
Petty Officer 2nd Class
- Joined
- May 10, 2005
- Messages
- 143
I purchased this motor this spring. Model #E150STLCUR. I will give you a little history. When I received the motor I changes the water pump ,did a decarb job with Seafoam, changed the oil in the leg and installed new plugs, Champion QL16V's. I checked the compression after the decard job and it was 95 psi on all 6 cylinders. First time out the engine started and idled fine. When I went accelerate it would pull up to 3000 rpm and then start to surge or miss. I took it back home and cleaned and put new kits in the carbs c/w floats. I took it out again and it once again started and idled great. It also accelerated hard right up to 5400 RPM. I drove it for approx. 15 minutes and then stopped to try a different prop. When I started it again the miss reoccured around 3000 RPM. If I sat it for awhile and let it cool off, the motor would run great, until it warmed up. then miss above 3000 would reoccur. I took out the plugs and noticed that the electrodes on the port bank of plugs were fouled and tnat starboard side plugs were light brown. I suspected a bad power pack on the port side. I replaced the port power pack. The engine ran great for the first 5 or so hours, never missed a beat. It then developed an intermittent surge or miss around 3000 RPM again. I checked the plugs again, the port bank of plugs looked fouled again. I went to swap the port and starboard power packs to isolate the problem. When I did I noticed that the bolt that grounds the the new power pack I installed was not tight (I was hoping that this poor ground was the problem). I then proceeded to swap the port and starbord power packs anyway to try and isolate the problem. This time I made sure that the mounting bolts and gound wires were secure. The miss I at 3000 RPM temporally went away but the engine stutters or misses right at the top end approx. 5400 RPM. I also noticed that my tach would cut out a times and the voltage would drop. I changed the regulator/rectifier. I hoped that this would fix both the tach and charging issued as well as the top end miss. The rectifier change fixed the tach and charging issue but did not solve the top end miss. Thats the history, here is my new problem.<br />Once again the engine starts and idles great. On the intial startup and the motor always runs great and does not miss a beat. It appears as it warms up it will develope a miss right on the top end or while I'm trimming it out. I can pull skiers and tubers all day long and run it under 4500 and it won't miss abeat. But as soon as it's I try and run it at WOT I get an intermient miss above 4800 RPM. I have pulled the plugs and the are all light brown. I had been running QL16V surface gap plugs. I changed to QL77JC4's. The problem is less intermittent with QL77JC4's than with the QL16V's. Is it possible that the power pack that has not been changed is going and that it only acts up intermitentley or on the top end? Could it be a coil, Stator or timing pick up? It's difficult to figure out because when I pull the plugs to check for the bad cylinder, all six are burning alike and the correct color (brown like toast, no fouling). Or is this a fuel/carberator problem? Sorry for being so long winded, I'm hoping that the history may make it easier to diagnose. Any thoughts, I'm looking forward to a response.
