stupid mixed gas question

[stackz]

ok, so last summer I was under the impression my oil injection pump was starting to fail on my 1990 90hp mercury engine. When I performed the factory test, it was nowhere near the cc output it should be.

I left it hooked up regardless as I didnt have anyway to properly bypass it. I couldnt find any info on exactly what the oil/gas mix ratio should be for the 10 gallon gas tank on the boat. I chose 32:1 and it ran fine. I put stabil in the tank over the winter and there was only about a quarter tank as it was. rebuilt the carbs over the winter and cranked it up last week with the newly rebuilt carbs. It ran great and throttle response was really nice. Took it to the gas station and filled the tank (approx 8 gallons went in) of ethanol free 91 octane. Added tcw oil to 32:1 per the bottle instructions and tossed it in the water at the landing.

I just could not get it to stay running for about 10 minutes and even then once I got it running I had to leave it choked or it would die and the exhaust smoke was quite thick. started raining so I pulled the boat and took it home.

after it stopped raining I hosed the boat off and hooked the muffs up to run it. It cranked up and ran but the exhaust smoke is still really thick. I'm thinking I have it mixed way to thick oil-wise and that the oil is hindering the plugs maybe.

What I dont understand is why it wont have a problem cranking and running while in the driveway vs just sitting in the water at the dock.

also, what I'm gonna do is pull the fuel fitting off the fuel line and use the bulb to pump gas out of the tank. I was thinking about taking 2~2.5 gallons out and then adding in just regular unmixed gas to help dilute out the gas mix in the tank.

does this sound feasable? or what would you do?

 

[MH Hawker]

Re: stupid mixed gas question

The mix should be 50 to 1 not 32 to 1, I would drain it all out and run it in my truck and then put the right mix in the boat. Your risking your motor playing with mix ratios if you dont know exactly how many gallons and so on. Drain the boat tank and do it right.

 

[oldjeep]

Re: stupid mixed gas question

or what would you do?

Fix the oil injection pump

 

[Texasmark]

Re: stupid mixed gas question

If you left it hooked up and had oil in the tank, and it was working properly you would be getting a 80:1 addition at idle up to a 50:1 at WOT. I have no idea as to the cc test so I can't comment on the validity of that saying anything about your pump's performance.

Assuming it was working you then add what you added so for 50:1 you are adding 2.67 oz oil/gallon and 32:1 you are adding 4 oz for a total of 6.67 oz per gallon which my arithmetic says you have a resultant 19.8:1 ratio.

I'd check my plugs.

To disable the pump just undo the hose to it, unscrew the two screws holding it to the block, pull it out and pull the gear and the little skinny thrust washer around the gear shaft out. Put everything else back including the hose and leaving oil in your tank to keep the low oil warning from coming on. Without the gear turning the oil will not come out of the pump outlet hose.

I have the 90 '02 model, basically the same engine, and just did my pump recently. Worked fine.

Then pour out your old gas and install 50:1 new and a new set of plugs. Then try it.

Mark

 

[ondarvr]

Re: stupid mixed gas question

32:1 is too much oil, it should be 50:1, plus you said you left the oil injection hooked up, so you have no idea how much oil is being supplied by the pump.

Motors can appear to run fine on a hose and still have problems, so it doesn't mean much.

 

[ondarvr]

Re: stupid mixed gas question

I just put a 90 HP Merc on my boat and it still had a full tank of 50:1 when I did, so it has run with oil injection and pre mix for a while. It doesn't smoke or run odd. I marked the level in the oil tank so I would know if was working correctly.

 

[stackz]

Re: stupid mixed gas question

Fix the oil injection pump

I'd love to but I cant find a rebuild kit for it. a replacement pump is over $200 :facepalm:

I mean if anyone knows where I can get a rebuild kit for one that would be awesome but I looked all winter.
90hp mercury serial OB275xxx

 

[UncleWillie]

Re: stupid mixed gas question

I chose 32:1 and it ran fine. ...cranked it up last week ...It ran great and throttle response was really nice. Took it to the gas station and filled the tank (approx 8 gallons went in) of ethanol free 91 octane. Added TWC oil to 32:1 per the bottle instructions and tossed it in the water at the landing.
I just could not get it to stay running for about 10 minutes and even then once I got it running I had to leave it choked or it would die and the exhaust smoke was quite thick. started raining so I pulled the boat and took it home.

after it stopped raining I hosed the boat off and hooked the muffs up to run it. It cranked up and ran but the exhaust smoke is still really thick. I'm thinking I have it mixed way to thick oil-wise and that the oil is hindering the plugs maybe...

I missed the part where you MIXED the oil with the gas.
If you filled the tank with gas an then poured in a pint of oil and started the engine;
The oil is just sitting at the bottom of the tank and gets pulled into the engine.

32:1 or 50:1 is not as big of a difference as the 2:1 the engine is getting.
Drain the tank, mix up the Oil/Fuel and pour it back in.
It is running better at home because the oil is starting to mix with the fuel due to the sloshing on the trailer on the way home.
Next time add the Oil BEFORE the fuel!

 

[H20Rat]

Re: stupid mixed gas question

I missed the part where you MIXED the oil with the gas.

Could be that, but I'd say its probably more likely the existing oil injection system... You can't premix AND leave the existing injection system there, even if it doesn't appear to be working completely up to the normal spec. Have to do one or the other.

 

[stackz]

Re: stupid mixed gas question

I missed the part where you MIXED the oil with the gas.
If you filled the tank with gas an then poured in a pint of oil and started the engine;
The oil is just sitting at the bottom of the tank and gets pulled into the engine.

32:1 or 50:1 is not as big of a difference as the 2:1 the engine is getting.
Drain the tank, mix up the Oil/Fuel and pour it back in.
It is running better at home because the oil is starting to mix with the fuel due to the sloshing on the trailer on the way home.
Next time add the Oil BEFORE the fuel!

yes I filled the tank and then poured in the oil, but this was at the gas station which is over 3 miles from the landing. so it still wouldnt have mixed up from the drive from the gas station to the landing? Only reason I did it this way is this is how most of my friends normally do it?

 

[stackz]

Re: stupid mixed gas question

regardless I'm going to pull all the gas out of the tank and fill it with a fresh 10 gallons mixed to 50:1 and pull the gear from the oil pump until I can either find a rebuild kit or find a pump for less than $200.

man I've got a LOT of weed eating ahead of me this year haha. thats about the only other 2-stroke I own

 

[zimm17]

Re: stupid mixed gas question

Don't listen to the other poster and pour that crap in your truck. If you know how much gas and oil are in the tank- you should be able to top it off and do the calcutations to dilute to 50:1. No need to throw out the gas because it has too much oil in it.

 

[81_chapparel194]

Re: stupid mixed gas question

regardless I'm going to pull all the gas out of the tank and fill it with a fresh 10 gallons mixed to 50:1 and pull the gear from the oil pump until I can either find a rebuild kit or find a pump for less than $200.

man I've got a LOT of weed eating ahead of me this year haha. thats about the only other 2-stroke I own

run it in your mower your car anything thats gasoline powered. wont hurt a thing

 

[joed]

Re: stupid mixed gas question

I would just drain it and see how much fuel you have. Then add the proper amount of gas to adjust the mix to 50:1.
For example 5 gallons at 32:1 has 20 oz of oil. 20 oz at 50:1 is 8 gallons, so just ad 3 gallons and use it.

Here is a link that will calculate it all out for you.

2-cycle Engine Fuel Mix Calculators

 

[dmoriarty51]

Re: stupid mixed gas question

dont use marine oil mixed gas in an air cooled 2 stroke, the oil is very different.....unless of course you want to buy a new weedeater. i drain my boats 50-1 mix into my truck at the end of the season every year no ill effects

 

[UncleWillie]

Re: stupid mixed gas question

...I filled the tank and then poured in the oil, but this was at the gas station which is over 3 miles from the landing. so it still wouldn't have mixed up from the drive from the gas station to the landing?...

Maybe, Maybe not! If the tanks is full there is not going to be very much sloshing going on.
3 miles is not very far or very much time.

Situation Summary:
32:1 was working fine for you before.
It was working OK before the fill up.
Everything happened immediately after the oil was added to a full tank.
Is seems to be working, not great, but better, after the drive home.

Do whatever you need to do to make sure the Oil is mixed completely in the fuel before trying anything else.
Occam's Razor : The simplest explanation is most likely the correct explanation.

 

[BobGinCO]

Re: stupid mixed gas question

what would you do?

Buy a four-stroke, and be done with that oil and gas mixing nonsense.

 

[UncleWillie]

Re: stupid mixed gas question

Don't use marine oil mixed gas in an air cooled 2 stroke, the oil is very different...

Would you care to elaborate on that?

 

[stackz]

Re: stupid mixed gas question

Do whatever you need to do to make sure the Oil is mixed completely in the fuel before trying anything else.
Occam's Razor : The simplest explanation is most likely the correct explanation.

how does this sound? I'll insert a length of garden hose down into the tank until it hits the bottom and then get my air compressor hose @ 40psi and just blow air into the tank to aerate it?

I figure why not lol. that'll get everything mixed up I would think.

 

[oldjeep]

Re: stupid mixed gas question

how does this sound? I'll insert a length of garden hose down into the tank until it hits the bottom and then get my air compressor hose @ 40psi and just blow air into the tank to aerate it?

I figure why not lol. that'll get everything mixed up I would think.

Sounds great, I'll bring the marshmallows.

Static from compressed air and fuel - what could go wrong?