Fouling 1 plug

[jerryjerry05]

About a 1982 50hp. 4 cy. Ser#5951619
Has good comp on all 4 about 150-155
Good spark on all 4
​I can change the plugs and the problem stays on #3
The reeds are ok.
The carbs spotless.
The fuel pump diaphragms both OK.

Starts and runs poorly.
The 3rd cyl. from the top carbons up real bad after a couple of min running.

The air screws are real hard to get anywhere close????
I don't see any blow back through the carbs.

Is it possible something in the exhaust chest has let loose?

Thanks,J

 

[Faztbullet]

Will it idle??? Can you hear a puffing in the carb area?? What does the deflector look like on top of piston,is it eroded?

 

[jerryjerry05]

It idles poorly.
Will inspect the crown.
​No puffing or blow back.

 

[jerryjerry05]

Inspected the crown.
​Nothing.

 

[jerryjerry05]

Owner said to look into it.
​Will post any updates.

 

[jerryjerry05]

FOUND THE PROBLEM!!!​Turns out it has a crack.in the block.

Thanks for the help.

 

[jerryjerry05]

More on the problem.
Kinda hard to tell even when it was completely torn down.

I was standing there scratching my butt and just happened to see a VERRRRRY tiny silver line on the side of #3(at first I thought it a scratch)
Pulled the pistons and cleaned the bore and found the inside with a network of cracks.

So problem SOLVED!!!

I'd like to THANK everyone who contributed to this thread.

I think the owners "buddy who knows everything" changed the impeller and gear oil.
The water tube grommet that fits in the top of the pump was gone/missing.
I think they used the boat and ran it hard?? and it got hot and the alarm didn't go off.
Got so hot that when they slowed down it blew cold water up in the cooling passages around the cylinders and the cracks appeared????
That's just a guess or the 1982 just decided to die??

Like I said thanks again.