Could 100:1 oil mix have hurt my motor?

a70eliminator · Apr 13, 2009

I messed up and added only about 5 oz of oil when I topped off with 4 gals. I was having trouble with idle and stalling out at anything less than full throttle, the engine had always ran like swiss watch.
Got it home and pulled the carb it was clean as a whistle, points were a little burnt so I dressed with a points file and reset gaps, plugs were all dark colored, I went ahead and checked compression to find 90 & 90 in the right bank and 75 & 60 in the left bank.
It was dark when I added the oil and the bottle was dirty and I couldn't see the oz. marks, but looking now in the light I see I didn't put enough oil in it, I would think it would have messed up all the cylinders rather than just one side?

tashasdaddy · Apr 13, 2009

Re: Could 100:1 oil mix have hurt my motor?

what motor? you could need a decarb, how many gallons of 100-1 did you run threw it? remember some oil is better than no oil.

alangf · Apr 13, 2009

Re: Could 100:1 oil mix have hurt my motor?

If all you were doing was light duty stuff the 100:1 should have been OK. That, as I understand it, is the range of VRO (from 50:1 for heavy loads to 100:1 for idling and light loads). Also, you added the 100:1 mix to some fuel that was properly mixed resulting in a mixture that was less than 50:1 but more than 100:1.

JB · Apr 13, 2009

Re: Could 100:1 oil mix have hurt my motor?

I don't think running one tank (or less) of 100:1 is going to damage a 50:1 engine.

This sentence: "I was having trouble with idle and stalling out at anything less than full throttle, the engine had always ran like swiss watch." doesn't make sense. Were you haveing trouble or not? Was that before or after you started running the 100:1?

A decarb treatment might bring it around, but that is a lot of difference for only a carbon buildup.

HybridMX6 · Apr 13, 2009

Re: Could 100:1 oil mix have hurt my motor?

Possible dirty carbs on the low comp side of motor? Making for low lubrication, thus now low comp?

Robj · Apr 13, 2009

Re: Could 100:1 oil mix have hurt my motor?

HybridMX6 said:
Possible dirty carbs on the low comp side of motor? Making for low lubrication, thus now low comp?

Sorry but the compression is low on all 4 cylinders. Retest and post the numbers. Might be time for an overhaul.

Have a great day,

Rob.

a70eliminator · Apr 13, 2009

Re: Could 100:1 oil mix have hurt my motor?

The motor, Evinrude Sportfour 1967 60hp. I've owned it from about 1980 and never had any stalling issues or rough idle problems, that is until just recently, It really seemed like the carb picked up some dirt or the float stuck or something of that nature because the low speed air adjustments were not responding and usually there very responsive to rich lean within a half turn, I had them seated in all the way it was still running! that never happens. I pulled the float bowl and inspected the cork float and needle & seat are fine, I reinstalled and ran a comp. 90-90-70-60 this is the first time I've checked comp. never had a need to she always ran great.
Well I gunked the cyls. down with seafoam overnight and I'm going to put the plugs back in and see what happens, I'll check compression again after it's run. Thanks.

a70eliminator · Apr 14, 2009

Re: Could 100:1 oil mix have hurt my motor?

Ok I ran the motor again yesterday and rechecked compression, still have only 75 & 60 in the left bank, I'm going to pull the heads just as soon as the gaskets I ordered arrive. I'll post some pictures of what it looks like.

freddyray21 · Apr 14, 2009

Re: Could 100:1 oil mix have hurt my motor?

as I recall those where low compression motors so 90 lbs is fine. I am thinking blown head gasket on the side that is low.

freddyray21 · Apr 14, 2009

Re: Could 100:1 oil mix have hurt my motor?

Robj said:
Sorry but the compression is low on all 4 cylinders. Retest and post the numbers. Might be time for an overhaul.

Have a great day,

Rob.

those are low compression motors so 90 is fine and not low compression.

a70eliminator · Apr 14, 2009

Re: Could 100:1 oil mix have hurt my motor?

Freddyray! you are absolutely correct as I just found this out while ordeing the (low compression) head gasket set. If it could only be that easy, my fingers crossed.

Tinman57 · Apr 15, 2009

Re: Could 100:1 oil mix have hurt my motor?

a70eliminator said:
Freddyray! you are absolutely correct as I just found this out while ordeing the (low compression) head gasket set. If it could only be that easy, my fingers crossed.

I had a 1986 Evinrude 25 hp and the manual recommended 100:1. Unbeknownst to me, Evinrude quickly changed the recommended ratio to 50:1. I ran that motor for 16 years at 100:1 and never had a problem. The guy I sold it to is still getting great service from the motor. It must have over 2000 hours by now.

Could 100:1 oil mix have hurt my motor?

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