Spark Plug Bent

[dahayes]

I have a 1988 VRO Evinrude 110 hp on a 1988 Stratos 266FS Fish & Ski. I just bought the boat and took it out for the first time. I was cruising along at 45 MPH when I heard a pronounced "click" in the engine. My speed dropped immediately to 30 MPH wide open. Later, I cranked it back up to take off and the nose of the boat raised up and that's as far as it would go. I might have been squeezing 10MPH out of it at best. The engine was cutting out really bad. A couple of days later, I pulled the plugs and did a compression test. The two left cylinders were 100 PSI, the top right cylinder was 92, and the bottom right cylinder was 82. Obvious problem there. When I looked at the plug that came out of that cylinder, something had hit it. And it hit it hard enough to drive the igniter down on top of the electrode. There is even a small shallow dent in the igniter where it hit and a small dent in the top of the piston as well. Not knowing what caused it and curious if it would run with a good plug, I replaced it with a new one and took it to the lake. The boat cranked fine, came out of the hole fine and topped out at 45 as before. I've only run it one time after that and it ran fine then as well. Any thoughts as to what you guys think could have hit that plug? Any help would be appreciated!

 

[interalian]

For a bent electrode and an accompanying dent in the piston top, only a plug with the wrong reach or a really loose conrod bearing/rod cap about to let go would make sense. If you put new plugs in and it'll do 45 again, re-check compression - that 82 is low.

 

[racerone]

Might as well accept that something is wrong.----Remove cylinder head and bypass cover to inspect your motor.

 

[F_R]

The bad cylinder swallowed something that got between the piston and spark plug. Now you have to find out what it was. You probably are not going to like what you find. But I would discourage you from running it any more till the question is resolved. A bad situation can turn into a catastrophic situation in a micro-second.

 

[Chinewalker]

I suspect you've got a broken piston ring or piston. Whatever broke bounced around inside there and smashed the electrode. It may, or may not still be in there as those bits tend to get flushed out the exhaust. Bottom line is something is very wrong inside there - as racerone said, pull the head and take a look.

 

[dahayes]

Thanks guys for the replies! I have enough experience with boat motors to know there is definitely a problem. The only way I'm gonna know for sure is to pull the head and see. I've heard everything from a piece of the ring, to a piece of the piston, to a piece of a reed valve floating through there and eventually getting between the piston and the plug. I'm just hoping it's a piece of the ring or the piston. If it's a rod bearing, there's a chance the crank could be messed up. If that's the case I might as well shop around for another engine...

 

[interalian]

You can check the rod bearing for excess play without removing the head. Just pull the plug and rotate the motor past TDC on that hole, then an inch or so on the downstroke. Push the piston with a screwdriver and see if it moves before the crank starts to turn.

 

[boobie]

What was the part # of the plug that got bent ??

 

[dahayes]

Interalian, I'll give that a try tomorrow. Thanks for the tip!

Boobie, I have the plug I took out on my desk at work. I'll let you know in the morning what the part number is. When I bought the new one it was very CHEAP! Like $1.69 cheap!

 

[dahayes]

Boobie, The part number on the plug is QL77JC4 and it's a Champion brand.

 

[dahayes]

I have another question about this. Someone correct me if I'm way off base here....If a rod bearing was coming apart enough to "spit" a piece of metal off and into the combustion chamber, wouldn't there be a tell tale noise coming from that cylinder when it's running? I've been in maintenance in a factory for a long time and my experience with a bearing coming apart usually means noise and excessive vibration....This engine idles and runs smooth and quiet now after I replaced the bent plug.

 

[racerone]

The compression numbers clearly indicate a problem.---Perhaps you do not want to accept the broken ring problem on your fine motor.----Remove the bypass cover and have a look at the top ring.----Will be a cost of $2.00 for a new gasket.

 

[dahayes]

I understand the low compression is a definite problem and I'm hoping it IS a ring. In fact, it might have had good compression until this happened....If a piece of the ring broke off, that could be why I'm losing as much compression as it is; I don't know. I've had several people tell me that it could be a bearing and I just can't get away from the fact there would be other tell tale signs to go along with it.

 

[F_R]

There just isn't any way to know what it was without an inspection. There are other possibilities such a screw from a reed or carburetor butterfly plate. These all are just educated guesses. Whatever the cause, you must tend to it.

 

[dahayes]

There's no doubt about that! Anytime something comes loose and flies around in the combustion chamber it's not good! Right now my boat might as well be a big flower pot! Because it's useless without a motor!

 

[dahayes]

Either way, whether I find out what hit the plug or not, the fact remains that it's 18 psi lower in that cylinder than the rest of 'em. That's definitely a problem that's not gonna fix itself! Lol

 

[racerone]

You start with opening the tool box.-----Remove bypass cover on the lowest compression cylinder.

 

[dahayes]

Racerone, are you a boat motor mechanic?

 

[racerone]

I could rebuild a motor like yours without a single glance at a manual !

 

[dahayes]

I could do it with some help. I recently tore down an old Mercury 115 "Tower of Power" and replaced all the gaskets and put it back together. I learned a lot. And I'll probably wind up tearing this one down before it's over. I have a friend that buys blown engines and rebuilds 'em and said he would help me. But he's promised to help me many times before and never has come through.