1976 merc 1150

[phatmanmike]

hello merc 1150 1976...<br /><br />ive read that these engines need different care concerning the oil ration and the fuel grade..?<br />is this true, is clams around to verify.....<br /><br />ive seen a lot of diehard I6 guys run high octane(some even with booster) and others with lead treatment.<br /><br />while others yet have the oil mixed at 40:1<br /><br /><br />m ikey

 

[jimmbo]

Re: 1976 merc 1150

Lead treatment makes no sense, these engines never needed lead. They might have slightly higher compression than todays but should run fine on 89 octane. 40:1 mix, some people figure under high stresss running slightly more oil is safer. I feel if the engines' bearings run smoothly at 50:1, more oil isn't going to make them run any smoother.

 

[achris]

Re: 1976 merc 1150

The 'lead' in fuel was to stop valve seat recession. Since two strokes don't have valves lead becomes redundant.... The octane booster is a reasonable idea. The higher the octane number, the slower the fuel burns. 20 years ago(ish) the octane number was at about 93.... so the fuel burn was "quite" slow. With todays crappy fuel at about 89 octane the burn is a lot faster (but releases less energy) and the risk of detonation is higher. Usually people running lower octane fuels will retard the timing a couple of degrees so that the expanding burn doesn't occur while the piston is still rising. <br /><br />Hope this helps (a little),<br /><br />Chris...........

 

[jimmbo]

Re: 1976 merc 1150

I believe your octane measrement/rating is slightly different Down Under than it is in North America

 

[achris]

Re: 1976 merc 1150

The method of rating is different, but the principles I have outlined remain the same.<br /><br />There are 2 methods of rating. One is the RN or 'research number', done by 'burning' the fuel in a lab and measuring the energy released, and the other is called the 'motor' rating, done by running an engine on the fuel in question and measuring the power produced. <br /><br />Chris..............

 

[jimmbo]

Re: 1976 merc 1150

I know the principles are the same but the numbers being different can lead to difficulty.