1992 Yamaha 40 Fuel Oil Ratio

[markt111]

the motor is a 40ELRQ, I am going thru this motor as I picked it up in the fall for my Minihawk, cleaned carbs, synching, adjusting linkages etc...

noticed in the manual it specs 100:1 ratio thru the oil injection at WOT... I thought all 2 stroke outboards were 50:1 should I add oil to the gas or is it safe to run 100:1?

[KIRCHNER]

i have a 25, pre-mix 100-1, no injection. no problems

[JPEROG]

Oil is cheap and it won't hurt the performance to fatten it up. Run Mercury or Yamalube at 50:1 and have worry free fun.

Joe

[markt111]

Oil is cheap and it won't hurt the performance to fatten it up. Run Mercury or Yamalube at 50:1 and have worry free fun.

Joe

Thanks I'll add some oil to each tank to fatten up the oil mixture, the oil injection pump is set to max at WOT already..

[sharpeye Mike]

I run my 50 Yam 50 to 1

[John S]

If it's working off an injection system (not premix), and there's no history of issues, I'd leave it be. Engineers designed it to operate with those parameters, so just throwing more oil can cause other issues, like poor idle, excessive smoke, which means incomplete combustion, carbon buildup, etc. too much oil will actually hinder the cooling properties of the mixture. If you can find a history of that design being insufficient, then yeah. But if you dialed it in to what the manufacturer spec'd, I see no reason to just add oil.

What would you alter the ratio to if you did? I will say, 100:1 sounds light. But those Yammie engineers ain't dummies. Maybe if you plan to run the thing full send the whole time or race???

[markt111]

If it's working off an injection system (not premix), and there's no history of issues, I'd leave it be. Engineers designed it to operate with those parameters, so just throwing more oil can cause other issues, like poor idle, excessive smoke, which means incomplete combustion, carbon buildup, etc. too much oil will actually hinder the cooling properties of the mixture. If you can find a history of that design being insufficient, then yeah. But if you dialed it in to what the manufacturer spec'd, I see no reason to just add oil.

What would you alter the ratio to if you did? I will say, 100:1 sounds light. But those Yammie engineers ain't dummies. Maybe if you plan to run the thing full send the whole time or race???

I will add enough oil to the fuel bring the total mix with the injection to close to the 50:1 ratio, 7-8oz per 6 gallons tank... If i get a significant build up or start fouling plugs I will cut back.

the motor was previously on a small pontoon on a tiny pond local to me and knowing the owner it was primarily used for sunset cruises (booze cruise) the motor most likely never saw 400RPM more than once or twice a season...

[FMP]

40:1 or better at WOT with typical 50:1 type oil. The 100:1 spec oil, the injection if calibrated to that uses the appropriate rate at WOT to achieve heavier than 50 direct comparison. Light rate at idle, probably less than 100 and probably more than 40 at wide open, which it needs. That's typical with oil systems.
If you were deleting the injection, using 50:1 spec oil you'd mix to 40:1 for wide open running or a bit more if really pushing it. If trolling around dragging lures it's way less , probably 100+ at 50 spec oil.