'74 Johnson 85hp

[Nullzero]

My brother bought a boat last year and didnt have a place to store it so I have it now. Good news for me Bad news is we took it out on the lake last week and it dropped a cylinder. No spark to one of the cylinders by pulling plug wires. Plugs are new so next step is testing the coils, I have a manual coming overnight because i'm hoping to get it up and running for the 4th.

I know my brother really hasn't done anything with the except put the new plugs in. So while i'm working on the spark issue is there anything else I should look over as preventative maintenance on the engine?

While we had spark to that cylinder it ran very well.

 

[jtexas]

Re: '74 Johnson 85hp

Pull the plug wire, no change in RPM's, that cylinder is either not getting spark, or not getting fuel, or getting too much fuel, or lacks compression. Spark tester (couple bucks at autoparts store), set at 1/2", will tell you whether you have adequate spark.

Preventive maintenance:
Water pump impeller, every couple or three years.
Lower unit oil, annually. I change mine in the fall before the first hard freeze, in case there's any water getting in there, don't want it to crack the gearcase.
Either take it out & run it every 2 or 3 weeks, or else add a fuel stabilizer.
Inspect the fuel lines under the hood every so often, replace 'em when they start showing signs of aging.
Top off the battery after a few weeks of inactivity.
Inspect the spark plugs couple or three times a year - google "reading spark plugs" to learn what to look for.
Compression test - do it now, write down the numbers as a baseline for future diagnostics.

have fun!

 

[tschamp20]

Re: '74 Johnson 85hp

rebuild the carbs!check compression just for piece of mind.grease steering tube.change lower unit oil.have you checked condition of impeller.its really pretty easy.hope it helps

 

[tschamp20]

Re: '74 Johnson 85hp

wow i guess it took me 3 minutes to type that.yeah what he said!!

 

[Nullzero]

Re: '74 Johnson 85hp

I'm pretty sure its spark not fuel it ran for about 15-20 minutes through a no-wake zone and a couple times up to plane as we were running it through its paces. Took the boat to a dead stop and then went to WOT and it took off great, shortly after that it dropped a cylinder. We took it to a dock pulled the hood and pulled plugs to find out which cylinder. The coil on that cylinder was not as warm to the touch as the other 3 so we were guessing that was the issue, or at least its the next one to try and rule out. I'll probably swap coils tomorrow after I get the manual though if I look at it tonight and it seems straight forward enough I might just do it without the manual.

As far as the rest of the list goes, thanks!

tschamp20 - you recommend a carb rebuild even if there's no sign of a problem?

 

[Nullzero]

Re: '74 Johnson 85hp

Ok opened it up and all four coils are cracked so I'll be replacing them regardless, its just a matter of time at this point before the rest go bad. I guess I should probably still swap them and make sure that it is the coil and not the power pack, but I'm hoping its just the coil.

 

[bigbob_FTW]

Re: '74 Johnson 85hp

i used some pig putty to repair the cracks in my coils. You could try this first to see if it works. I think a 2 part epoxy would work as well, as long as its not metalic based.

 

[Nullzero]

Re: '74 Johnson 85hp

bigbob- I'm guessing you mean on the coils that arent failing but are cracked once it has failed epoxying it shut isnt going to help anything right?

 

[bigbob_FTW]

Re: '74 Johnson 85hp

bigbob- I'm guessing you mean on the coils that arent failing but are cracked once it has failed epoxying it shut isnt going to help anything right?

Mine had hairline cracks in the case allowing the current to arc out to the mounting plate. the epoxy will only seal the outer case. if the coil has internal damage, this won't help.

 

[Nullzero]

Re: '74 Johnson 85hp

hmm I'm going to have to try that, thanks for the tip.

 

[tschamp20]

Re: '74 Johnson 85hp

was thinking if the boat sat for awhile they can get gummed up.just preventative maint. thats all.get ready to spend some money hahahahaha

 

[bigbob_FTW]

Re: '74 Johnson 85hp

hmm I'm going to have to try that, thanks for the tip.

You really have nothing to loose. Mine was running very bad, and now purrs like a kitten. If it didn't work, i would have just replace the coils, but thats a lot more $$$. good luck.

 

[Nullzero]

Re: '74 Johnson 85hp

well took it out tonight after putting the epoxy on, still dropping cylinders but it seemed to be more intermittent tonight than it was before IE it would kick back in every once in a while. I guess I'm gonna have to just replace them. but yeah woulda been a nice $3.50 repair.

 

[tschamp20]

Re: '74 Johnson 85hp

run it tonight on the muffs when its dark and see if there is a spark coming from the coils.