Johnson 115 No spark on one cylinder

[racerone]

As I said these motors all have the same problems.----I would never trust a 20 year old powerhead to be good and trouble free without a tear down and full inspection.

 

[Bob_VT]

Let's get the heads off and inspect. Make sure it was not the head gasket. If it was mine I would do the rebuild which would make me more comfortable in the future knowing what is inside the motor. I do understand that it cramps your current season.

 

[adelainey]

I don't think I would have the know how to do the actual rebuild myself. Not even sure if there is a place in my city that can rebore cylinder walls on outboards. I think I am going to order a remanufactured power head. Any suggestions of a reliable seller ?

 

[Bosunsmate]

have a go at the rebuild, they arent that complicated the main thing is to just take photos when you take it apart so you know how to reassemble.
i taught myself and my only mechanical knowledge comes from meccano.
it will save you a lot of money and its quite enjoyable to see how they operate, you wont regret it.
Once you have the powerhead off the actual putting in of new pistons and putting it back together can be done in a morning easy.
lots of people on here have done such rebuilds so ask as many questions as you do it, its winter here so im around a lot, my farms quiet for a while yet.

first thing to do is to remove the leg out of the way and then strip down the electrics and flywheel taking pics as you go.
Once you get the starter and everything off, the motor is actually liftable by hand although a pulley system helps.
i did a 90hp not long ago, its very similar to that motor, the only special tools i used was a $10 flywheel puller and a $30 toque wrench

 

[adelainey]

One thing I worry about is if the cylinder walls are too far gone I won't be able to get big enough pistons. I really would enjoy doing the rebuild myself. And I have seen kits for around 600. But I would like to go with wiseco pistons. I am sure there are kits that come with them.

 

[adelainey]

One thing I would like to know is after the rebuild what would be break in procedures.

 

[Bosunsmate]

The only time ive had trouble with walls is when roller bearings have got in there, it doesnt sound like that in your case but you nevver know so i only order parts after ive teared it apart and got my eyes right in there.

Break in procedures easy, just varying the hp for few hours.
On motors ive rebuilt ive just put in a replacement piston, warmed it up on muffs with a good 50/1 oil mix for about twenty minutes on idle with some alternating slightly higher rpm and then gone out for a joyride

 

[adelainey]

Ok. So I took the heads off to have a look and the side with no compression looks like just worn pistons. Cylinder walls are smooth as can be. With the other side it looks almost perfect. Now I am for sure gonna do a rebuild. Should I do all 4 pistons and rings or just 2 new pistons and new rings on all 4? And I am assuming I should hone the cylinder walls as well?

 

[Bosunsmate]

good stuff
id do rings on all, new upper and lower seals, waterpump, full gasket kit, new connecting rod screws for the new pistons
You can hone if youd like,
when i come across good cylinder wals i just give them a bit of a rough up with very light sandpaper to get rid of the glazing.
Remember to keep everything very clean

 

[adelainey]

Should I replace bearings as well?

 

[Bosunsmate]

up to you, depends how much you want to spend, just the big end bearing is about $55 for one.
definitely inspect the ones from the broken piston for pitting etc, you can then consider whether its worth checking the others
if the bearing cage is ok you could take the roller bearings to an enginneering shop, they can often supply same size ones very cheaply.

 

[Bosunsmate]

one thing to be aware of when disassembling piston connecting rods is that the caps must always go back on the same rod.
getting the cap to sit perfectly on the rod that it came off is one of the few crucial tasks when reassembling.
the rods are made whole and cut in half in the factory so each cap must go with the rod it was cut off.

 

[Bosunsmate]

check the flywheel for play before you disassemble as thatl tell you if top bearing needs replacing,
ive never had to replace either top or bottom

 

[Bosunsmate]

looks like only the bottom bearing is available anyway

 

[racerone]

The rods are fractured at the factory.---The caps will fit perfectly when carefully assembled.--This takes some time to make sure all is correct on assembly

 

[adelainey]

Great advice everyone. Will keep all this in mind while doing the rebuild. I am hoping to have the parts this week and will let everyone know how it went. Big thank you to everyone who has contributed.

 

[adelainey]

One more question which I have asked before but just want to make sure. As I said the cylinders look real good still. I have measured them and they are all slightly smaller than spec allows according to the shop manual. Is it absolutely necessary to have the cylinders bored and honed? And what kind of surprises can I expect while tearing down the power head? I am getting nervous about doing this Appreciate any feedback

 

[Bosunsmate]

No its not absolutely necessary at all. I just rough up the glazing that has happened on them with some very light wet sandpaper. The glazing that occurs overtime reduces compression
You can buy a honer for about $10. You only need a small/medium one, they just attach to a powerdrill. Ive never bothered with them as sandpaper works for me

Not sure what that means about the bore size, have they grown in size to now be too small???
I wouldnt worry about something being slightly out of spec, just run 50/1 premix oil and thatl be fine.

Just take heaps of photos so you know how things should go back and have a clean secure work area so you dont lose bits, apart from that its just step by step taking apart, replacing and then doing it back up.

 

[Bosunsmate]

The only surprise you will probably get is how heavy the crankshaft with pistons is.
Take a photo of where its sits and how everything looks after you split the crankcase.
Those crankcase bolts are tight so make sure you get the right size socket on them
Also if you only plan on doing the damaged piston then itd be easier if you left the crankshaft in there and just undo the damaged piston connecting rod.
remember to always keep the pistons connecting rods and caps together as one unit. i have four ice cream containers that i put them each in.
postsome photos if you can as im interested to see whats going on.

 

[Bosunsmate]

heres a 90 hp i did a while ago, it will probably be very similar to what you have