Spark Plug Condition

[markustyson]

Ok. Here is my #2 plug on my 3-cyl 78 Johnson 70 hp. The 1 and 2 plugs look pretty good. Is this carbon fouling?

My symptoms are power loss at high rpms. It will run fine at low rpms, but loses power once I use more throttle. Plugs are new with about 2 hours of use. Could I have an ignition coil issue?

Thanks. This is a wonderful forum. I am new to boating.

 

[Fuzzytbay]

Re: Spark Plug Condition

That looks more like melted aluminum to me, but I can't say for sure. If it is melted aluminum, it can only come from one thing.....your pistons. Have you had any adjustments to yoiur carbs or fuel system lately?

 

[jtexas]

Re: Spark Plug Condition

uh-oh...it does look like metal...what's your compression?

welcome to iboats!

 

[markustyson]

Re: Spark Plug Condition

I have not had a chance to check the compression. I'm thinking of just taking the thing to a mechanic.
I have cleaned the carbs with carb cleaner but haven't taken them apart for a good cleaning. I have two fuel tanks and I get the same problem.
I'm really hoping that it's not aluminum. When I replaced the plugs from all of the old ones looked great.
Thank you for all of your help. I will be sure to post results when I find them.

 

[Silvertip]

Re: Spark Plug Condition

Spraying the carbs does absolutely nothing since the cleaning agent does not get inside the carb where problems lurk. Disassembly and thorough cleaning is the only way to do that. I agree that this looks like metal transfer, likely due to lean operation or preignition (timing issues). Overheating can also contribute to both situations. Does your alarm system work? Without it you have no idea if the engine is hot.

 

[markustyson]

Re: Spark Plug Condition

Okay. Thanks for all of the info. It's currently in the shop getting looked over so I will post my findings soon. Thanks again!!

 

[F_R]

Re: Spark Plug Condition

Hopefully the problem is fixed by now. But I'm wondering about that plug. Is it the right plug for the motor? Doesn't look like it from what I can see in the picture. A too-hot plug can cause pre-ignition, which will melt or break pistons.

 

[markustyson]

Re: Spark Plug Condition

Just got the boat back. Not so good news. Mechanic looked at it for 20 mins and has determined:
1) Compression for that cylinder is way down (don't know actual number)
2) Aluminum walls are scored and show signs of melting

They didn't charge me for this diagnosis, which is nice of them, but he did recommend that the engine is toast and to buy a new one.

Well I don't have the money for a new one so I'm not sure if I should keep the boat and sell the motor for parts, or sell the whole thing.

How bad is it to run the engine on only 2 of the 3 cylinders? If I put a "cooler" plug in there, will that help?

 

[clemsonfor]

Re: Spark Plug Condition

The only thing you can do is make it more toast. If you want to tear into it you can tear that motor down and pull the piston and rod and it will run rough on the two cyls. Seriously i would not run it , it wont run better, the cooler plug will help nothing, its scoring now. You could part it out and try and buy a used motor on a crap boat for a deal and then throw the other boat out and runthe motor on your boat.