OK to dilute 50:1 oil premix for use with 4-stroke engine?

[fxykty]

Our fully inflatable dinghy for several years now has a short shaft Suzuki 15hp 2-stroke outboard. As we’re heading for crocodile country we decided to buy a used 3.6m tinnie. The tinnie has a full transom and requires a long shaft motor, so we can’t reuse our current outboard. The tinnie came with a long shaft 15hp Mercury motor, but it’s a 4-stroke (model 10185030 2003 model year).

Unfortunately we had just mixed and filled 15l of 50:1 oil/fuel for our 2-stroke.

Several people have told me I can just dilute to 100:1 and run that through the 4-stroke. Is that OK? Or do I risk something gumming up?

[Wotname]

While I am no expert, I would expect a 100:1 mix would be OK in a 4 stroke outboard engine; it might even be helpful. I would be happy to try it.

[Tupaia]

I ran my 4 stroke dive compressor on premix. Remote place no other fuel. It was smokey and I needed to clean the plugs a couple of times until it was used up.

[rslifkin]

As long as you dilute it enough that you're not getting noticeable smoke or fouling the plugs, it won't hurt anything. A tiny bit of 2 stroke oil will add cylinder lubrication, it's only too much that causes problems.

[Chris Cringle]

So you want to take a chance on causing your outboard to fail to save the cost of of 15 liters of petrol and a little bit of o/b oil? In crocodile country no less. Brilliant!

[thinwater]

Shoot, back in the day I drove old cars that used 100:1 (a quart of oil with every fill-up)! Yes, they would need the plugs cleaned ~ 500 hours, but there were multiple reasons for that. And that was 4-stroke oil, not 2-stroke oil.



Dilute it about 200:1 and don't give it another thought. It won't even carbon the plugs.

[Timryl]

For $30-40 worth if fuel, in top end country, remote, really remote - why not stuff a sock in the carby inlet as well?
Donate the fuel to someone else. Volunteer Coast guard?

[thinwater]

Anyone that has actually burned 100:1 or 200:1 in an engine please comment. I have many times. This is much ado about nothing, you won't even carbon a plug with a tank or two. There will be no difference you can detect. Really.


Normal forum over-cautiousness.

[capt jgw]

I used to dump my left over 50:1 gas in my pickup truck every fall when I laid up the boat. Sometimes as much as 6 gallons (about 24 liters). Never a problem. That was an old truck without a catalytic converter though, I wouldn't do with with my newer car. I assume the newer 4 stroke OB does not have a cat either, the worst it can do is foul the plugs a little.

[Wotname]

If the o/b is a EFI engine, it might even be beneficial; if a carburettor engine, then don't leave the mixed fuel dry in in it.

And yes, I have often dumped left over mixed fuel into the car and agree with what thin posted

Anyone that has actually burned 100:1 or 200:1 in an engine please comment. I have many times. This is much ado about nothing, you won't even carbon a plug with a tank or two. There will be no difference you can detect. Really.


Normal forum over-cautiousness.

[Quadrille in JB]

Wow, there a lot of naysayers out there with no experience and no qualifications to answer this. Back in the day I worked at the Evinrude/Johnson test center as a driver and we would change fuel and oil types often while trying to get the two strokes to burn unleaded fuel without seizing up. This was all pre-mix and as the test boats were refueled each time they came in we would simply roll the boats on their cradles out and fill everybody’s car up with pre-mix. Nobody ever had any problems including fouled plugs. If you get really rich on the oil it could cause problems because it actually leans the fuel mixture out. Good luck with your new rig.

[Auklet]

Maybe dilute the fuel mix to 100:1, dump it in the car tank where it becomes even more diluted, and start w/fresh fuel for the 4-stroke. Geeze. There’s theory, testimonials, and hopefulness but I would not want to be out there with big crocs around hoping my 20-yr-old engine does not foul out b/c it didn’t happen to an anyomous on-line testifier in FL or elsewhere. Who you gonna call! I also think I would service it before departing. I have one that old (i.e., 2000 Tohatsu) that I service every couple of years or so or as needed (e.g., when starting and idling issues appear).

[JPA Cate]

@ Auklet:

So far as I know, fxykty live aboard their boat and do not own a car at this time. They are cruising the "top end" of Australia.

Nice folks.

Ann

[GILow]

Nothing like a nice bit of top end lubricant. I've run small four strokes on 25:1 from time to time. No problems at all.