Evinrude 90 HP O/B - Fuel Mixture Blunder

[muswell_hillbilly]

Just bought my first boat and was anxious to get it out on the water. Bought it knowing the fuel gauge didn't work, and after fiddling with it a bit decided to take the boat out. To be "safe" I figured I'd add a half tank (10 gallons) to be certain not to run out. I added the right amount of oil and headed for the gas station. Only problem is that there was already 16 gallons in the tank! I could only get 4 gallons of gas into the tank!

So my mixture is off, and I'm not certain how concerned I should be. Here's how I've figured it:

- 16 gallons properly mixed fuel already in tank => 41 oz oil.
- Oil I added for intended 10 gallons gas => 26 oz oil.
- Total oil for 16 gallons already in tank => 67 oz oil.
- Added 4 gallons of gas to tank => 20 gallons gas.

So my net mixture is 20 gal/67 oz => 38:1. Does this make sense?

I did run it with this mixture for a while, figuring it would be O.K. as long as I kept adding straight gas into the tank until mixture was correct. Was this an O.K. assumption?

Thanks!

 

[Fl_Richard]

Re: Evinrude 90 HP O/B - Fuel Mixture Blunder

Id take it out and fill @ 50:1 from now on.

A little extra oil wont hurt anything and there less to wory about. Dont forget to decarb once in a while.

 

[Phoenixfirewalker]

Re: Evinrude 90 HP O/B - Fuel Mixture Blunder

no problem just carry new plugs with you.
the plugs will carbonize just as the cylinders
new plugs and a can of seafom to 1 galon of gas to de carbonize and clean.
thats all
but the engine will be safe

 

[JB]

Re: Evinrude 90 HP O/B - Fuel Mixture Blunder

Some additional oil is no problem, hillbilly. You might get more smoke than normal and a bit more carbon buildup if you use that 38:1 for a long time, but for one tank. . . no worries.

Remember, that engine was run on 24:1 for break-in.

 

[muswell_hillbilly]

Re: Evinrude 90 HP O/B - Fuel Mixture Blunder

Thanks for the feedback! Wow - this board is impressive! I've only posted twice and the feedback has been prompt and useful - thanks!

I'm relieved to hear that running 38:1 for only partial tank shouldn't be a problem. This is a one-time mistake that I'll be careful not to make again (i.e. fix the fuel gauge!). My guess is that I used 2-4 gallons @ 38:1, so if I replace that volume with straight gas, I should be close to correct mixture.

Thanks again for the support! Hopefully I can return the favor to some other rookie after I get a few years under my belt...

 

[Home Cookin']

Re: Evinrude 90 HP O/B - Fuel Mixture Blunder

even with the guage fixed you won't know how much gas you can put in. Mix the oil at the gas station while you fill the tank: a pint, then 6 gallons, then a pint, 6 gallons. If your last 6 won't fit you aren't too far over.

 

[Boss Hawg]

Re: Evinrude 90 HP O/B - Fuel Mixture Blunder

even with the guage fixed you won't know how much gas you can put in. Mix the oil at the gas station while you fill the tank: a pint, then 6 gallons, then a pint, 6 gallons. If your last 6 won't fit you aren't too far over.

Thats absolutly correct but its easier to put 6 gals in then add a pint
If the last gas is only 3 gals to fill then just add bout 1/2 pint & you'll be good -
Over time unless you come home every time with a MT tank your mixture will get really screwed up cause you'll never remember how far over/under your 50:1 mix was at last top off