OX66 250 Neutral RPM

[jf123]

What is the highest RPM I can run this engine in neutral safely?

[boats.net]

The specs are 700-760 rpm's in neutral.

[jf123]

I am trying to find an imtermitten misfire that seems to come in at higher RPM'S. Can the engine sustain say 1500-2000 RPM in neutral for short periods? Or higher/Lower?

[boats.net]

Yes it can as long as you are not trying to shift into gear at that speed.

[robert graham]

I believe that it's generally accepted not to run motor much over 1500 RPM's while in neutral. Of course, everyone probably has, but it's not supposed to very good for the motor. I use a fast warm-up idle in the 1000 to 1200RPM range. Good Luck!

[jf123]

I foul cylinders 3 and 4. Plugs come out looking like they were dipped in paint. Covered over in a hard carbon. With the heads off pistons and head chambers have a heavy deposit of carbon like tar. I have been having this problem going on two years . Always the same two cylinders. Spark, fuel, compressions is all there. At idle she purrs like a kitten once I run her after about an hour or so I get the misfiring and both plugs are fouled. I have access to a spare engine so every parts has been swapped out except the block, flywheel and wiring harness. Injectors sent out etc. Since I'm out of the water I cannot do any loaded tests. My only thought is I'm losing spark or compression on those two cylinders. I see nothing in the wiring diagrams that would isolate those two cylinders. Any suggestions welcome. If you can check your diaghrams to see if specific wires from the stator and pulser coil affect 3 and 4 that may help me pinpoint. The diaghams in the service manual I have do not go into detail.

[Tucker]

JF did you ever find the probelm? I've read about this on other forums. I have the 150 and would like to know you problem solving process on this one.

[jf123]

After opening it up water seems to be the culprit. Still didn't find where it is coming in at and I'm not sure I ever will. It gave me ten years of trouble free service so I can't complain. New powerhead will be going on in the next few weeks. If I find the source of the leak I'll make sure to let everyone know.