I have a US 41, still never been run, just getting ready to make a stand to put it on to break it in.

But I happen to have the original Owner's Manual, it says the following:

Your engine has been factory tested with an 18x8 prop at 7,000 RPM. After break-in, we recommend an 18x10 or 18x12 prop, however, othe rprops can be use dupon experimentation, egines develop optimal power between 7200 and 7700 RPM.

One-way bearing should be lightly oiled with 30 weight oil every 15 to 20 hours and/or prior to storing engine for any length of time.

The general operating fuel mix recommended is 32:1 using 87 octane reg unleaded fuel and high quality two-cycle engine oil. Always mix well.