Oil on front engine cowl
 

Right after landing I did a quick walk around my 337G and found oil on the front engine nose cap, roughly as shown in brown in the figure (it was brown, not red). Didn't have time to check further.

In the 1.5 hour trip went through some hevy rain. And on arrival was ordered to do a go-around and for about 10 seconds I had full throttle but only 2450 RPM (everything worked OK for the remaining 10 minutes or so that it took me to land). Pending an inspection, do you think I have a problem or could one of these two events have caused oil to flow over the nose cap?

Ernie

There is a problem, most likely a minor problem. Without looking at the engine (de-cowled) or prop (without spinner), it would be difficult or impossible to determine either way.

It could be engine oil or it could be prop grease in that area.

I don't think that your particular flight operation had any impact or cause to this though.

Dave