spark plug gap closure on '74 model johson 115hp

[warreng]

Having same problem as pblarus had back in 2002. Gap on spark plug in #4 cylinder slams shut. Heard about decarbonizing engine and was wondering if anyone has had any luck correcting this problem using this method? Also have been advised that needle bearings or wrist pins could be the problem. Should I decarbonize? Maybe insert different plug to see if this happens to another plug? Any help is greatly appreciated.

 

[Hooty]

Re: spark plug gap closure on '74 model johson 115hp

What sparkplugs are you using? I suppose you could try decarbonizing but I'd be forced to remove the head and have a look. Have you checked the compression?<br /><br />c/6<br /><br />Hooty

 

[warreng]

Re: spark plug gap closure on '74 model johson 115hp

I'm using Champion L77JC4's (they came in the motor when I got it). I just put the motor on the boat and haven't checked the compression. Motor hadn't been started for two years. Noticed this problem when I pulled plugs to lubricate before tarting. Engine has spent it's entire life in freshwater lake in Dallas area. Everything on it looks to be brand new. When I check the compression, what should I be looking for in terms of numbers? Will the QL77JC4 plug make any difference? It was recommended by a local dealer.

 

[ob]

Re: spark plug gap closure on '74 model johson 115hp

warreng,Before I cranked that engine over I would install a new Champion plug gapped to spec and manually rotate the engine with the flywheel and make certain that there is no mechanical interference.Hooty offers sound advice in removing the head and have a looksee.Ground straps on sparkplugs don't bend shut unless something between them and the piston dome pushed them shut.

 

[warreng]

Re: spark plug gap closure on '74 model johson 115hp

Thanks for all the sound advice. My background with repairing anything usually involves tearing apart, looking at it and forgetting how it all goes back together, so this ones' going to the shop. Once again, I appreciate everything.

 

[Hooty]

Re: spark plug gap closure on '74 model johson 115hp

When it comes home from tha shop, would you pull this posting back up and let us know what the problem was? I'd like to know and I'd bet there are a few others who are curious.<br /><br />g/luck & c/6<br /><br />Hooty

 

[steelespike]

Re: spark plug gap closure on '74 model johson 115hp

It appears that motor is designed to use surface gap plugs.While there is something going on with that cylinder a surface gap plug would probably clear up the problem.

 

[ob]

Re: spark plug gap closure on '74 model johson 115hp

According to this chart the QL16V surface gap is listed first for that engine but it lists the QL77JC4 gapped at .030" as optional. web page

 

[fish4970]

Re: spark plug gap closure on '74 model johson 115hp

as far as compression goes all cylinders suould be about even <br />not more than 10% between the highest & lowest cylinder

 

[wgroomer]

Re: spark plug gap closure on '74 model johson 115hp

I'm the same guy as warreng, just two different logons for work and home. The model # for this engine is ESL11573M, so i'm assuming it's a '73 instead of a '74. I pulled the head off this morning and don't notice the #4 piston traveling any further than the #2 piston. Pushed both pistons back by hand after reaching TDC and don't notice any slop at all in either piston. Checked to make sure the plug isn't seated in the head any further than the other plug and they were seated exactly the same. Would same surface gap plug be recommended for this engine? It's been raining here for a month. Any suggestions on how much horsepower required to move a 1600 square foot house to Arizona? (Fully loaded with wife and two kids).

 

[ob]

Re: spark plug gap closure on '74 model johson 115hp

wgroomer,Yes the same surface gap plug is listed for the 1973 model according to the chart provided above.Bare in mind that after rotating piston in question to TDC that if there is any slop in the piston to rod that it won't be detected by pushing in on the piston but rather puling out.Was the dome of the piston in question caked with carbon deposits?<br /><br />Try rocking the flywheel to and fro and see if you note any slop in that pistons movement that is not present in the adjacent piston on the same bank.