Mariner 25hp, 50:1, forgot oil.

[sammymcnally]

I know how stupid this was, but there was a quarter tank 50:1 and I filled the 5litre can with straight unleaded. I ran it for 6 miles and it stopped. In neutral it's pumping water, and did turn over and re start, but as soon as gear was engaged it stopped. I assume I have wrecked it, but if I take out the spark plug and put some oil (or anything else??) in it, will it stand a chance? There was a crunching noise when gear engaged. Makes me think the cylinders are shot. Again, I realise what a dope I have been. But all advice gratefully received. Thanks. It's an old mariner 2 stroke, approx ten years old.

 

[sammymcnally]

Should have also said that the pull cord still works and pulls out ok. I had assumed that seizure would have prevented that, but I know very little about outboard engines to be honest.

 

[tpenfield]

:welcome: to iBoats . . .

Oil in the cylinders and into the intake would be good to get some oil back in the engine. Compression test would be a good next step. That should tell you something about the condition of the engine.

 

[flyingscott]

Do a compression test before anything.

 

[sammymcnally]

Thanks both. I took out the plugs and put in some Valve spray, then poured in some oil and then gently pulled it through. It works a treat now. Really appreciate your advice, some relief! There was also a green wire on top of the engine which had become disconnected. There are two green wires actually - but only one had come off. I'm starting to wonder if that was the problem... Thanks again Ted and FlyingScott.

 

[ajgraz]

The green wires are likely switch box to ignition coil, one or both of those being loose could cause the stall under load.

 

[jimmbo]

If there is damage, oil is not going to repair it. I would pull the exhaust cover off and look at the piston skirts for signs of scuffing/scoring. The bearings for the crankshaft, connecting rods, and piston pin are all roller, ball or needle, but still may have been damaged, but only a teardown may reveal that.
What speed did you run the engine at for the 6 miles? There was some oil in the gas, if thoroughly mixed it would have been about 200:1. Unless you shook the tank as you added gas I doubt the fuel was completely mixed and a slight richer mix remained at the bottom of the tank.