Evinrude 88 SPL having to use extra oil when mixing

[Slyder760]

Just wondering if anyone could explain to me why I am having to put extra oil in when I mix my oil and gas. I have a 1990 Evinrude 88 SPL and since I purchased the engine if I mix it 50 to 1 it will run about 30 mins then lock down and score the piston on bottom left side. After this happens you can add extra oil to it and change that plug and it will straighten up and run on. Normally I just mix it extremly rich it smokes a good bit but runs fine so long as I do this. Was just wondering if maybe it is on its last leg or maybe i'm doing something wrong.....example....over the weekend I mixed it 50 to 1 and it locked down in the middle of the lake after only 10 mins. or so...trolled to shore and added 16 more ounces of oil to the 4 gals or so of gas left and she fired up and played for about 3 more hours. Any comments or suggestions as to why this is would be great thanks!!!!

 

[daselbee]

Re: Evinrude 88 SPL having to use extra oil when mixing

It is running very lean. You need to rebuild the carbs, which is a very common cause of running lean.
Pay special attention to the high speed fuel circuits, make sure the HS jets are absolutely clear.
It is right on the hairy edge, and the extra oil prevents the seizing.

I would be surprised if there has not been serious engine damage already.

 

[emdsapmgr]

Re: Evinrude 88 SPL having to use extra oil when mixing

A couple of thoughts: 1. Maybe the horn in the control box is not working and it's overheating and you are getting an overheat lockup. 2. An engine I had did this. After the powerhead blew up, I found the skirts of the piston had thick, carbon buildup all around the skirt. The carb buildup was so thick that it blocked the cooling oil/fuel mixture from getting to the ringsets. Even though the engine ran cool, the crown of the piston eventually overheated and locked up in the cyl. Cracked all the bridges on the exhaust side. It's good to run some Engine Tuner throught those crossflows occasionally for just that reason.

 

[Slyder760]

Re: Evinrude 88 SPL having to use extra oil when mixing

Well I recently went through both carbs(2 months ago) and did a very good cleaning and rebuilding on them because of another issue I was having with it not accelerating to wot. The engine will still push the boat through the water at 41 mph on a semi-choppy day. By the way its on a 16 ft stratos 355v weighing in at 900lbs. So I don't think it would be the carbs but I could always be wrong Im only human. How would you test to see if it was overheating if the horn isn't working because I have never heard the horn go off at any point in time? And is it possible to get the carbon off the pistons without a rebuild if that was the case?

 

[toddschubert]

Re: Evinrude 88 SPL having to use extra oil when mixing

Use an infrared thermometer to measure temp of each head. They should run about 145-155 deg.

 

[toddschubert]

Re: Evinrude 88 SPL having to use extra oil when mixing

Also to check horn alarm. Disconnect each sensor (brown wires) and short them to engine ground. This should bake it beep if alarm is working.

 

[Chinewalker]

Re: Evinrude 88 SPL having to use extra oil when mixing

If your motor has locked up repeatedly, I'll bet the damage has been done. Adding the extra oil is masking the problem, not fixing it. More than likely you've got a carb issue. Just because you rebuilt them two months ago doesn't mean a new issue hasn't cropped up. All it takes is one carb getting a slug of water or gunk and the motor will run itself into the ground if you keep nursing it along...

 

[emdsapmgr]

Re: Evinrude 88 SPL having to use extra oil when mixing

I'd probably pull one or two of the intake side covers (they are called bypass covers in the parts lists) off. Once these are off, you can view the sides of the pistons and ringsets as you rotate the flywheel by hand. You should be able to see if there is any carbon around them and also on the piston skirt. Check to make sure the rings are intact. These covers come off easily and the replacement gaskets (if that's not the problem) are cheap.

 

[daselbee]

Re: Evinrude 88 SPL having to use extra oil when mixing

^^^^^^^^

Now that is a great point. Easy to inspect on a crossflow. Good call.

 

[Silvertip]

Re: Evinrude 88 SPL having to use extra oil when mixing

You've answered your own question. That cylinder has been scored -- apparently more than once. Now, 50:1 is not enough oil to overcome the effects of the scoring. As pointed out, more oil is masking the problem -- not making things normal. Continuing to do what you are doing will only make matters worse to the point where you will need 10:1 to keep it running. After that -- "Bang!"