ALuminum n spark plug

[bigbadchevy89]

I have a 1979 100 hp Johnson Javelin. My buddy pulled the plugs at the end of last year and found aluminum on one of them after developing a a miss on the lake while running at wot. He does not remember what cylinder it came from. I replaced the plugs and still have a miss. I found water in my fuel and replaced with all fresh fuel. My over heat alarm never went off but does work and I am still pumping water. Where do I start in my diagnostic with this engine. Is this going to even be worth fixing? Any and all input would be greatly appreciated.

D.C

 

[Davem3]

Re: ALuminum n spark plug

my best guess would be to pull the head, and check the pistons. go from there?

found aluminum on one of them, makes me think a cracked piston, or maybe they were not the right plugs and the piston was hitting the plug?????

and model number, and pictures please........... makes it easier to help out

welcome to I Boats

some parts will be easy to find, but first we needs a model number

 

[bigbadchevy89]

Re: ALuminum n spark plug

I am currently not near the engine. I will get the model number off it it Friday. Where is the best place to locate the model number? A guy at my work who claims to know what he is talking about told me I should also do a compression test does that make any since?
D.C.

 

[Davem3]

Re: ALuminum n spark plug

yes do a compression test as well, the model and serial number should be on the mount somewhere, usually on the starboard side of the mount

the important thing on the compression test is to have the all of cylinders within 5% of each other, or then we are looking at a head gasket( common) rings or a piston ...............

 

[bigbadchevy89]

Re: ALuminum n spark plug

thank for the info. From what I understand I am just hoping it is not the block itself. I hope this is an easy fix I miss my boat!!

 

[jbjennings]

Re: ALuminum n spark plug

Aluminum on a spark plug is a sign of detonation or lean condition making the cylinder too hot. Either way, I'd clean all carburetors and recheck timing advance. It may be advancing too far too fast, causing detonation.
I would not run the motor again until you clean the carbs and recheck the spark advance/carb. synchronization.
JBJ

 

[bigbadchevy89]

Re: ALuminum n spark plug

Jbjennings:
I am in the process of trying to find a manual on this engine. I have to get the exact model number in order to do this. Does anyone know where I will find a product specific service manual and not something that covers tons of different models like a clymer manual.

 

[daselbee]

Re: ALuminum n spark plug

Your compression should be around 120 psi. Aluminum on the plugs...the damage is already done.

Find the cylinder that is low, pull the head, don't break any head bolts, and you will see a severly eroded piston probably on the exhaust side, probably with the side eroded away all the way down to the top ring.

I certainly hope it is not that bad. Please post back exactly what you find. Maybe pics too.

Get your manual from www.kencook.com, or find one on ebay. No Clymer, no Seloc, no CD.

 

[daselbee]

Re: ALuminum n spark plug

How about this one?

http://www.ebay.com/itm/1979-omc-ev...56490248&pt=Motors_Manuals_Literature&vxp=mtr

 

[Silvertip]

Re: ALuminum n spark plug

Don't rush to conclusion that timing suddenly got out of whack. It is more than likely a lean condition which points to carburetion. You can pull the plugs, rotate the engine so you can see the top of the piston and I think you will find the conclusion obvious. One of the pistons probably has a hole in it or the edge of it is burned away so a compression test would reveal which cylinder is the issue. Regardless -- metal deposits on a plug is an indication that a tear down is required. Period!

 

[emdsapmgr]

Re: ALuminum n spark plug

As was mentioned, do a compression test. No point in going into much expense if one hole is dead. The aluminum transfer is as a result of too much heat and not enough fuel to cool the piston. I'd be inclined to pull the head and check the rubber water diverter by the overheated cyl. If it is misshapen, clogged with debris, or out of position-you can get a cyl overheat and it may not set off the hot horn. You can also get a good look at the piston crown. Check the cyl walls for scuffing (aluminum transfer.) Also pull the carb off that feeds that piston and check the high speed jet on that side of the bowl for debris/restriction. Any restriction in the jet will lean out the fuel/oil flow to that cyl. If you have original fuel hoses on that engine- they were not made to handle today's ethanol fuels. I've seen black bits of deteriorated fuel hose lodge in the carb high speed jets...

 

[bigbadchevy89]

Re: ALuminum n spark plug

As was mentioned, do a compression test. No point in going into much expense if one hole is dead. The aluminum transfer is as a result of too much heat and not enough fuel to cool the piston. I'd be inclined to pull the head and check the rubber water diverter by the overheated cyl. If it is misshapen, clogged with debris, or out of position-you can get a cyl overheat and it may not set off the hot horn. You can also get a good look at the piston crown. Check the cyl walls for scuffing (aluminum transfer.) Also pull the carb off that feeds that piston and check the high speed jet on that side of the bowl for debris/restriction. Any restriction in the jet will lean out the fuel/oil flow to that cyl. If you have original fuel hoses on that engine- they were not made to handle today's ethanol fuels. I've seen black bits of deteriorated fuel hose lodge in the carb high speed jets...

Thank everyone for all of the input I cannot wait to get to the engine this weekend and see what is going on.

D.C.