Older motors smoke and newer ones don't. WHY?

[Bearcamp]

I have a 1972 Johnson 15 hp and run the fuel 50 to 1. I also have a 1994 15 hp Evinrude and run the fuel 50 to 1. Why does the older one (low hours) smoke more than the 1994 Evinrude? Is it because the newer one has electronic ignition and the older one points? And what can be done to reduce the smoke on the older one? I've heard that running synthectic oil might help. What about hotter plugs?

 

[DJ]

Re: Older motors smoke and newer ones don't. WHY?

You have over 20 years of tecnology improvements that add to the difference.<br /><br />However, make sure your older engine is in top running condition. DO NOT use a hotter plug, you may want to perform a decarb for best compression.<br /><br />Synthetic oil MAY help.<br /><br />Decarb procedure here.<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016

 

[jimmbo]

Re: Older motors smoke and newer ones don't. WHY?

First of all they didn't make a 15hp in 72. they did have one in 1956. A 15hp wasn't back in the line untill 1974. and has been a regular since.

 

[Bearcamp]

Re: Older motors smoke and newer ones don't. WHY?

Heyyyyyy good, it's newer than I thought. I was tolf it was a 72 but you say 74, OK.