Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

[gnorm]

Last fall my 90hp Evinrude VRO V4 engine started bogging at high throttle. I had limp it at about 1500 rpm to the launch. I took it to the marina to check it out and fix it. I figured it was because of old gas considering it doesn't get used much. Later the marina said it was old gas in the tank. Drained it, cleaned the carb, put in new plugs, and said it was ready for winter.

Last week I put in fresh gas since last Fall, hooked up the ear muffs to the water inlet, primed it with the squeeze bulb, after several cranks (ignition switch pushed in for choke) it reluctantly came to life. I ran it at mid range to keep it from stalling until it warmed up. It blew a lot of oil which I thought was residual from sitting. After several minutes the rpms started to climb on its own. The engine got smoother then rough then smooth again. I figured it was enough and had to get home.

Yesterday I went to crank it and nothing happened. Battery was good so I tried to hand spin it thinking the worse. It was tight. I pulled the plugs to relieve the compression for turning and noticed the #1 cylinder plug had fused the tips together. I immediately pulled the head and saw the damage. The top of the piston had melted in an area the size of a quarter with lots of aluminum pellets and chunks in the cylinder. Aluminum is smeared on the cylinder walls and no sign of residual oil. The other 3 cylinders and plugs appear fine. What happened?

I have to admit the ear muffs were shaken off but only for a few seconds. I know what happens to the impeller and cylinders with no water so I shut the engine off and replaced immediately. I'm not convinced this caused the meltdown. Could have this been an ongoing issue since last year and finally rearing its ugly head? This engine always started hard and had issues since I bought it 6 years ago. One thread here says it could be lack of oil in the high rpm range due to a clogged high rpm jet in the carb?

Oh yeah, never heard an overheat alarm.

 

[multimech]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

Sounds like a piston detonated. That is usually from too little fuel (lean) of which it sounds as if it adds up on your motor.

 

[James R]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

A failed cylinder head gasket could have allowed water into the cylinder causing the problem. Have just finished rebuilding a 115 and the only thing that may have failed was the gasket. No hole in the piston but piston aluminum all over the plug. Carbs had been cleaned and running on 50:1. VRO had been removed and a standard fuel pump fitted. This eliminated the possibility of a VRO issue prior to the failure.

 

[multimech]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

The melted part of the piston tells me it got hot. The chunks are probably part of the wrist pin bearing which would have failed due to a lean condition. Which pullls all of the information you have described all together.

 

[gnorm]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

Okay, how to fix it...

• Buy piston (.010 over?)
• Buy rings (.010 over?)
• Buy head gasket kit
• Hone the cylinder/remove aluminum
• Install pistong and rings
• reassemble head, etc
• Find root cause????

 

[multimech]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

To do it the right way.

1. Have the bores inspected for depth of cut needed to get out any scoring. This will determine the size of piston(s) The machine shop will also check for out of round and warping of the block.

2. Have the entire block to the machine shop, they can also machine any parts that may not be flat any longer. Everything will be sure to seal up then.

3. Take the shops advice on the needed parts and go with that, or you could have trouble down the line.

4. New thermostats.

5. New water pump.

6. Carbs and fuel system thoroughly gone through.

7. Fresh fuel. Add oil to the fuel if you have a VRO.

8. Carefully check ignitions system. Double fires. Timing.

9. Go have fun!

 

[emdsapmgr]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

Would be nice to know just what caused your failure. Why not pull the carb apart that fed that detonated cylinder. Pull the jets out and visually inspect them-esp the main jet on that side of the carb. Possible the jet is restricted and caused a lean condition. Also, now that the head is off, check the placement of the rubber water diverters by each cylinder liner. If one gets out of position, it can disrupt/resrict water flow around a cyl. When that happens, you may get an internal cyl overheat and never hear a warning (overheat) horn. You certainly need to know this before you start reassembly and testing on a rebuilt powerhead.

 

[gnorm]

Re: Model E90TLCDC(86?)Evinrude 90 HP VRO toasted piston

Tore down the engine. Found the rubber stops in the correct places. Piston melted on top mostly near the exhaust side with smeared aluminum on the cylinder walls. All other cylinders look good .Only the #1 damaged. Around the con rod, cylinder, wrist pin all dry as a bone. Found a 1/8 inch crack at the top of the cylinder. Took the block to a shop and got the cylinder re-sleeved. He honed the other cylinders and said all were good. Re-assembled the power head and re-installed the wires. Next to look at the carbs and fuel lines tonight for air leaks, blockage, etc.

When I first took it to the marina for repair he said he wouldn't touch it due to the cracked sleeve. He also suspected detonation. Could it be the damage was already done last summer as it ran like crap and limped back to the boat launch? Then with new fuel this year it just gave it its last high rpm run in the driveway before it locked up?

Would be nice to know just what caused your failure. Why not pull the carb apart that fed that detonated cylinder. Pull the jets out and visually inspect them-esp the main jet on that side of the carb. Possible the jet is restricted and caused a lean condition. Also, now that the head is off, check the placement of the rubber water diverters by each cylinder liner. If one gets out of position, it can disrupt/resrict water flow around a cyl. When that happens, you may get an internal cyl overheat and never hear a warning (overheat) horn. You certainly need to know this before you start reassembly and testing on a rebuilt powerhead.