I just bought a dinghy. It has a 2001 15 hp Johnson model j15rsib. How do I tell if it is 2 stroke or 4?

Get the model and serial number off the engine and call one of the outboard dealers in Detroit along the river. They'll be able to tell you.

GFC, Wyoming is on the good side of MI, it's outside of Grand Rapids.

Look for a oil filler cap. If it exists, its likely a 4 stroke. However, many 2 stroke engines also have oil injection for their larger engines - whether or not it includes 15hp or not, I am not sure. For many of the smaller 2 stroke engines, you still have to mix oil yourself (I have to with my 2004 Mercury 5hp dinghy motor)

I am going to guess though that it is a 2 stroke, as I don't think Johnson makes any small 4 stroke engines.

But I don't know for sure, so best thing is to look up the model number on-line or consult a dealer.

Look here:

http://www.usboatsupply.com/pdf/EJ/ModelNumberRefGuid2005.pdf

Apparently, a 4 stroke would have a 4 in the model number.

Use your nose when its running.

See if you can lift the engine without trouble.

Also on a 2 stroke, there should be somewhere inicating to mix oil 50:1 in the gas, or some other ratio.

Thanks for all input, after much looking around, (tanjacap is my husband) he was able to verify it is a two stroke. Working great.