Hello, Ive got a 1990 70 hp evinrude ob, what is the right octane fuel to use. I have read some of the info here and at marine max just want to be sure, thanks for the help, tvman
Hi, TVMan.<br /><br />Your boat will go faster if you buy premium.<br /><br />Your wallet will be lighter, therefore the boat will be lighter and go faster. <br /><br />If you buy premium for your tow vehicle, too, the boat will go even faster. <br /><br />Of course, you wont notice or be able to measure the increase in speed, so regular seems the right way to go.
Continued use of high octane fuels in engines designed for 87 octane will create engine deposits in the combustion chamber, ports and plugs. Higher octanes run cooler thus the engine will not burn the fuel as efficiently. High octane fuels are for high compression engines to prevent them from preigniting during the compression stage of the stroke. Because of the high compression the engine using normal 87 octane would also run too hot. Good HIGH quality low octane gas ACTUALLY burns cleaner and with more power if the engine is set up for it.
To dispell myths:<br />This is from this page: web page <br />WHAT IF I PREFER TO USE GASOLINE WITH HIGHER OCTANE RATINGS?<br /><br />You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system. It can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly. In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline.<br /><br />And for you guys that REALLY want to learn somthing, check this one out: web page
<br /><br />If you buy premium for your tow vehicle, too, the boat will go even faster. 
