Spark Plug Color on Seized Outboard

[karl3419]

My 1978 70HP Johnson has been running fine until Saturday. The engine knocked a couple of times and then froze up. After taking out the spark plugs I still could not turn the flywheel more than a couple of degrees. Looking at the plugs two are black and oily and one is a dusty brown. Does this indicate what happened to the negine? Thanks

 

[Chris1956]

Re: Spark Plug Color on Seized Outboard

It could mean lean running or overheat. Why not remove the transfer covers and look at the condition of the piston and rings?

 

[karl3419]

Re: Spark Plug Color on Seized Outboard

[I am sorry but what are transfer covers? My shop manual does not show this name in its diagrams. It shows a "cover".

 

[boobie]

Re: Spark Plug Color on Seized Outboard

Or else pull the cyl head and look. Could also have a locked up gear case.

 

[jrs_diesel]

Re: Spark Plug Color on Seized Outboard

Usually the exhaust plate is on the left side for the inline engines. Gives you access to the exhaust cavity and the exhaust ports.

 

[Chris1956]

Re: Spark Plug Color on Seized Outboard

Transfer covers are usually on starboard side of motor. These allow fuel to transfer from crankcase to cylinder. Since there is no waterjacket there, the bolts usually do not seize up like on the exhaust covers.

 

[karl3419]

Re: Spark Plug Color on Seized Outboard

I removed the head and everything looks normal except the pistons are not staggered. #1 piston is back and #2 piston is back even with #1. #3 piston is full forward. I am assuming that a connecting rod has broken or the rod cap has come off. Obviously the powerhead must be pulled for further inspection of the crankcase and rods. Now I am trying to decide if the engine is worth repairing. Problem in replacing it is it is one of a pair so I would like some matching.

 

[boobie]

Re: Spark Plug Color on Seized Outboard

Just for S & G's pull the g/c off before you do anything else.

 

[karl3419]

Re: Spark Plug Color on Seized Outboard

Just for S & G's pull the g/c off before you do anything else.

Thanks for your reply but I am sorry but I do not know your abbreviations. What is "S & G" and "g/c" ?

 

[rockyrude]

Re: Spark Plug Color on Seized Outboard

s***s and grins, gearcase

 

[karl3419]

Re: Spark Plug Color on Seized Outboard

s***s and grins, gearcase

I was following the procedure in the Service Manual but you recommend removing the gear case (lower unit?) first. Does this make it easier to remove the powerhead?

Let me ask your advice as I have not decided what to do yet. This engine is one of a pair. I can either replace the powerhead with a remanufactured one or look for a complete used similar 70 HP outboard engine. Any suggestions?

 

[rockyrude]

Re: Spark Plug Color on Seized Outboard

What boobie is saying is pull the lower unit to rule out a locked up lower unit. It's a lot cheaper to pull the lower unit and see if the power head now turns freely than to start throwing money blindly at it.

 

[karl3419]

Re: Spark Plug Color on Seized Outboard

What boobie is saying is pull the lower unit to rule out a locked up lower unit. It's a lot cheaper to pull the lower unit and see if the power head now turns freely than to start throwing money blindly at it.

Rockyrude - Just some more information. I removed the head earlier and the pistons are not staggered as they should be. #1 and #2 are fully back and #3 is fully forward. This gave my contacts the conclusion that a rod has broken or a rod cap has come off and jammed the crankshaft. Is this the wrong conclusion?

 

[boobie]

Re: Spark Plug Color on Seized Outboard

It may be best to listen to your "contacts" !