posted 06-07-2007 10:35 PM ET (US)            

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I have seen the same 100:1 in my Evinrude 48 SPL docs but later found on the web they switched back to recommending 50:1. I have a 1984 model. I think I saw it on the Evinrude website but it has been documented elsewhere.

Here's a thread on the same topic where someone also recommends 50:1. The last post mentions 100:1 or 90:1 but states 5.5 gal to a pint which is actually closer to 44:1.

continuouswave.com/ubb/Forum3/HTML/005043.html

[Deleted link to a calculator for figuring fluid volume ratio. The calculator had too many advertisements associated with it. Calculators are not much value when you are out in the boat. Print out a cheat sheet if you cannot do the math--jimh.]

posted 06-08-2007 10:10 AM ET (US)            

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Nope...break-in is ALWAYS double the oil for a certain period. So if it is supposed to be 100:1 then during break-in you would run 50:1. Even with VRO you run oil in the gas as well as the pump until say 10-20 hous of break-in. The only engines so far that do NOT require this is the E-Tecs which do it automatically via computer control. Now the old thought was oil is cheaper than metal so why not just make her a little rich. This is not necessarilly good for the engine as it can cause carbon buildup and stick rings. Most think it justs fouls plugs but that is just a short term problem. Your best bet is to ALWAYS run as close to the stated mixture ratio. With these particular engines they flipfloppd around with mixtures so both are fine but I would tend to run it richer unless all you do is slow speed running. Again mine was 100:1 and I ran it like 75:1. If mine stated 50:1 I would have run 50:1.

The truth is 50:1 is what an engine needs at WOT. So technically if you NEVER run WOT then you can run your 225hp at 100:1 and not have a problem but....at what engine speed is 100:1 good for? 4400rpm? 3375rpms? who know so hence why you run at stated mixture. Supposable the VRO runs an engine at 150:1 at idle and 50:1 at WOT and varies in between. Newer E-tecs and such probably run somewhere like 300:1 or higher.

posted 06-08-2007 10:20 AM ET (US)            

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meterdoc,

I recommend you run that motor on a 50:1 fuel/oil mixture. In the 1980s OMC developed motors so well built they were happy running on a 100:1 mix. But what OMC later found was that not enough oil was being left on the cylinder walls to prevent internal rust. The official recommendation at that time was it is OK to run 100:1 if you run the motor on a daily basis, but otherwise the motor will be better off running on 50:1.

The performance of the motor is the same either way, jut a little smokier with 50:1. As a practical matter and motor that is older, just run 50:1 and play it safe.