85hp problems

[imported_JamesL]

Hi guys,
Started up my 1979 85hp v4 the other day and it was running badly. I pulled the leads off the plugs one by one and found no difference when i pulled the lead of no 3. There was good spark tough cos it gave me a really good zap.

I pulled the plug and it was really gunked up with what looked like muddy water. What would cause this?

Thanks heaps

James

 

[ezeke]

Re: 85hp problems

The probability is that you have very little compression on that cylinder. If you can get a screw-in compression gauge and take the readings, someone here will take you to the next step.​

Check the compression on all holes with all plugs removed, using the same method for each cylinder. Write them down for future reference.

If you want to skip that step and pull the cylinder head first, then buy a head gasket.​

 

[imported_JamesL]

Re: 85hp problems

I did a compression test and all and got 115, 118, 108, 115. 108 on the problem cylinder. Do i need a new head gasket or could it be somthing else??

Thanks for the reply.

 

[HighTrim]

Re: 85hp problems

Your numbers look good. A 10 percent difference is ok, and you're well below that. When pulling your plugs, you should use a platic plug boot puller, dont wanna get electrocuted, lol. Try actually checking your spark, should jump 7/16 of an inch.

 

[ezeke]

Re: 85hp problems

If the plug looks gunked up, so is the rest of the firing chamber, piston and rings. You might want to consider a decarb; instructions are found on the Engine FAQ forum here:

http://forums.iboats.com/showthread.php?t=158076

 

[imported_JamesL]

Re: 85hp problems

Ive wanted to do a decarb for a while now. Im from Australia and we dont have seafoam here. Ive looked everywhere even contacted seafoam and they said they dont send it out here. Are there any alternatives that i could use?

 

[emdsapmgr]

Re: 85hp problems

You shouldn't see any water in the cylinder. Possible you are seeing a mix of water and the normal gas/oil mixture. A slight amount of water leaking into that cylinder will cause it not to fire. Very possible that you have a blown head gasket. I would pull the head off that side and have a look. If you don't find anyting unusual, check the exhaust cover. I have seen water ingested back into a cylinder from a porous casting-leaky/cracked exhaust cover.

 

[imported_JamesL]

Re: 85hp problems

Should i decarb the motor or just bull the heads and put new gaskets on?