'83 and/or '92 Evinrude 115hp #1 cylinder scoring

[Zigblazer]

I have a 1983 Evinrude 115hp V4. Model E115TLCTE. Got it 3 years ago, rebuilt the lower unit, rebuilt 1 carb, replaced the other, replaced all 4 coils and 1 power pack, along with all the fuel lines big and small. Ran great most of the time. Have it on my 24ft pontoon went through 2 props trying to fix a ventilation problem. When it ran well it, and didn't suck air, it would push about 20mph at about 5000 rpm. When it didn't it would max out at 10 mph around 3000 rpm. Seemed random, didn't happen more hot or cold. I tried different coils, plug wires, power packs, checked head temps, and couldn't find a problem, or make it change how it acted. I believe it was dropping a cylinder when it was having the problem. There would be a small pop and it would run great again. When I got it, it had around 110 psi in all 4 holes for compression. It looked like it had been rebuilt at one point in time, and today I took off the heads and confirmed that it had. It had 0.030? over pistons and some sort of poor mans porting on the ports. I'll admit I'm not a 2 stroke tech in the least, but I've rebuilt a few car/truck engines and worked on trucks for a few years, so I figure I can at least replace parts. I usually slow down to a crawl and keep testing it until it pops and works right again.

We got plenty of use out of it around the 4[SUP]th[/SUP], and it seemed to be running as well as ever, rarely had a problem, and it would only last a minute or two when it did. Then it wouldn't snap out of it towards the end of the week. At the same time it became really hard to start and keep running. I could get it to start, but it would stall if I idled down to shift into gear.

I tried again after it cooled down. Didn't want to snap out of the bad running again. I gave up and got sick of trying to figure out what was going on and took it into a dealer. It took a week before they even looked at it. They called and told me compression on #1 cylinder was only 30 psi and # 3 was 80psi. They said #1 was very scored and it needed a rebuild. They did not tell me what would have caused it, or cause my intermittent low power, which was what I asked in the first place. If I am correct in my thinking, I'm guessing it had a fuel problem getting to #1 and when it would be low on power it was starving the #1 cylinder. Most of the scoring is from the top inside ports (closer to the opposing cylinders). I'm not familiar enough to know if they are the intake or exhaust ports, but that's where the scoring starts.

I picked up a 1992 115hp Johnson today with a known scored cylinder. Took the heads off, and found scoring in the same place and the same way as mine. Along with some piece of metal that ran through and destroyed the piston.
The VRO is long gone on both.

What causes scoring in the top left of the #1 cylinder starting at the top of the ports? I'll try rebuilding to get one good powerhead, but would like to correct the cause of the problem before I ruin another motor.

Any ideas?

Also is there a good shop to have the block bored and prepped anywhere around Duluth or the twin cities?

 

[interalian]

#1 being the highest cylinder is most prone to overheat problems. How do the deflectors look? They're the little rubber slugs in the water jacket you can see when you have the heads off. The deflectors can dislodge or swell.

 

[emdsapmgr]

Cylinder scuffing is caused by excessive heat, which can result from lack of lubrication. First thing to do is an autopsy on the carbs throats that fed the scuffed cylinders. You may find the main jets have some debris in them, restricting gas/oil flow. That results in heat and eventually the cyl liner scuffs. You can have the same scuffing results if the one cylinder runs hot. For instance, if the deflectors (mentioned above) get out of position, that can stop/reduce the flow of cooling water around that cylinder. This type of failure will also result in scuffing, but may not set off a hot horn, as the water pump and thermostats are still working normally. The head may be cool to the touch. The problem from the first overhaul may have been that the original problem/issue was never resolved. Such as you can overhaul the whole block, but if the deflectors are out of place, the new engine will just start overheating. Another thing, check the nylon valve body inside the thermostat housing. There are two pinholes (later blocks have one oval hole.) If these holes plug up, the powerhead can overheat, even though the telltale is spraying good. Before you get the rebuild underway, make sure you have a knowledgeable tech look a the block to assess just why you have the failure. Then figure out if you want to put out the $ for repairs.