Johnson Sea Horse 1965 5hp LDL10S

[nathanglasgow]

Just fitted new head gasket(compression great,no scoring of bores) coils,condensers,points and spark plug wires and spark plugs(champion J4J as stated on makers plate on the engine) and engine would not start.Fantastic spark at plug leads, jumps more than 1/4 ".When plugs are attached to leads and are grounded they also spark.When plugs put back in head and motor pulled a few times they have fuel on them(carb also cleaned and rebuild kit fitted).Very dissapointed this old lady did not start after having these parts imported to Scotland where i live!!!.Anyway after pulling the starter rope till i had blisters in desperation i put in a set of used NGK B6S spark plugs from my old 1972 chrysler 30hp and the the little bugger started.Can anyone shed any light on this because it beats me.Many thanks to all replies.Nathan

 

[eavega]

Re: Johnson Sea Horse 1965 5hp LDL10S

Silly question, but are the plugs correctly gapped?

-E

 

[F_R]

Re: Johnson Sea Horse 1965 5hp LDL10S

Simple rule of electricity: It follows the path of least resistance. When you had the plugs out in open air, the path of least resistance was across the gap. In the cylinder, under compression, the path of least resistance was through whatever deposits or something that was shorting them out.

 

[nathanglasgow]

Re: Johnson Sea Horse 1965 5hp LDL10S

Yes silly question! Champion J4J were gapped correctly .20".These plugs were brand new and my question was why did the engine fire with some old NGK B6S plugs and not with the correct new plugs.I have tried putting the new plugs back in when the engine was cold and the same thing happens,no fire, but when the old NGK plugs put in it runs like a dream.I'm thinking it has something to do with heat range or plug reach.

 

[nathanglasgow]

Re: Johnson Sea Horse 1965 5hp LDL10S

Sorry plugs gapped to .30" and points to .20".Its 0.30 in the morning here in Scotland so the brain is tired and the body is going to bed.In conclusion this restored motor(new water pump and impeller and all gaskets,pistons and bores clean as a whistle,cylinder head decarboned and lapped) runs great with the wrong plugs in so that is how i'm going to use it.I was just curious if anybody could give me an idea why this is so.Cheers for now.

 

[nathanglasgow]

Re: Johnson Sea Horse 1965 5hp LDL10S

Just a quick update.Sourced two new old stock champion J4J plugs and put them in(yes gapped to .30") and motor starts and runs well with no problems.Put the old J4J's back in (remember these were new never used before plugs) and guess what-No start.This means the first set of 'new plugs' have some kind of problem or manufacturing fault.They have sat in their boxes for about twenty years and visually looked okay.Plugs don't go bad with time do they?Anyway it has been a lesson in not trusting new parts.

 

[freddyray21]

Re: Johnson Sea Horse 1965 5hp LDL10S

new parts can often be bad. Odd to fine a matched set of bad plugs, but not impossible. could be a cracked insulator shorting out to ground when they are in. Doesn't take much of a crack.

 

[samo_ott]

Re: Johnson Sea Horse 1965 5hp LDL10S

Very odd. But good to know. Glad you got it running.

 

[Shizzy]

Re: Johnson Sea Horse 1965 5hp LDL10S

as a kid the 5HP Tecumseh I had on my Mini bike lost spark. new coil didnt fix it. spark was dead. I yanked the plug off the snowblower (old Montgomery wards ) and she fired right up. So yes a plug can be bad and look or be new

 

[nathanglasgow]

Re: Johnson Sea Horse 1965 5hp LDL10S

Just a quick update.This little engine has been pushing my Westerly Cirrus 22ft yacht since the beginning of April.Has about 25hrs of useage since rebuild and starts first pull most times.Having no neutral or reverse makes you a better sailor when approachig pontoons!Compared to the price of a new 5hp this wee thing owes me nothing now.Uses about 2lt per hour at 3/4 throttle.