Johnson 5HP Outboard troubles

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Keith 66

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I have a Johnson (OMC) 5hp outboard, 2 stroke made in year 2000, on the info plate it says model J5RSI Its a single cylinder engine.
I got given it about 20 years ago & it had been very little used, we used it to get our sabre home prior to her refit & it performed faultlessly.
Since then its barely been used & as such is a bit of a timewarp engine basically looking nearly new.
Last year on one of its rare outings it conked out so i stripped & cleaned the carb & float bowl plus fuel tap filter. At that time i treated it to all new fuel hoses cos the old ones had gone rock hard.
It was pressed into use last weekend for my sons new boat for which it is ideal, Started 3rd pull & ran fine opened it up & performance was excellent.
After about 6 minutes it just slowed down petered out & stopped, water was coming through & it didnt seize nor seem unduly hot.
Wouldnt start again. Next day put it on the tank & ran it for 20 minutes & seemed a bit rough. Seems like a fuel problem to me but could it be a dying coil?
Any ideas? Im a bit loth to flog it & replace with another unknown engine!
 
Sounds like you know more about this than me but...

Don't dodgy coils usually act up when warm? So would be very suspicious of that.

Plug oiling?

Failing that, as you say, fuel. Does the tank and filter look clean? Fuel line kinked?

Don't ditch the engine, it sounds like a gem.
 
Keith 66 said:
I have a Johnson (OMC) 5hp outboard, 2 stroke made in year 2000, on the info plate it says model J5RSI Its a single cylinder engine.
I got given it about 20 years ago & it had been very little used, we used it to get our sabre home prior to her refit & it performed faultlessly.
Since then its barely been used & as such is a bit of a timewarp engine basically looking nearly new.
Last year on one of its rare outings it conked out so i stripped & cleaned the carb & float bowl plus fuel tap filter. At that time i treated it to all new fuel hoses cos the old ones had gone rock hard.
It was pressed into use last weekend for my sons new boat for which it is ideal, Started 3rd pull & ran fine opened it up & performance was excellent.
After about 6 minutes it just slowed down petered out & stopped, water was coming through & it didnt seize nor seem unduly hot.
Wouldnt start again. Next day put it on the tank & ran it for 20 minutes & seemed a bit rough. Seems like a fuel problem to me but could it be a dying coil?
Any ideas? Im a bit loth to flog it & replace with another unknown engine!
Click to expand...
I think you will find that is a rebadged Suzuki !

Have you tried a new plug? It should be a NGK BRP7HS-10 gapped at 0.035" (0.9mm)

Check the strength of the spark .. It should be strong enough to jump an air gap of around 10mm.

Check the compression, but if it starts Ok that's probably Ok

Clean the carb again.

Are you just using the internal fuel tank or do you also have a remote tank ?
 
Last edited:
VicS said:
I think you will find that is a rebadged Suzuki !

Have you tried a new plug? It should be a NGK BRP7HS-10 gapped at 0.035" (0.9mm)

Check the strength of the spark .. It should be strong enough to jump an air gap of around 10mm.

Check the compression, but if it starts Ok that's probably Ok

Clean the carb again.
Click to expand...
You could try adding Seafoam to the fuel. It worked a treat when my Yamaha was doing the same thing.
 
Thanks for the replies, I didnt know it was a rebaged Suzuki, Its got clean new fuel, just using the internal tank. Will try a new spark plug.
Any source in the Uk for a manual for it? Only one i seem to get pointed to is the twin cylinder version!
 
The first thing to check when a motor won't start or conks out, is to remove the plug and check it for fuel. A wet pug indicates bad ignition and a dry plug indicates lack of fuel. Of course very first thing to check if a motor stops after a while is the tank vent is open. ol'will
 
Tank vent was clear, It seemed to peter out from lack of fuel.
Anyway got it in the workshop now & looking at it the only thing i hadnt stripped & cleaned was the crankcase mounted fuel pump. Took it off & first thing i noticed was the small section of rubber hose that connects it to the crankcase was quite loose, So i suspect an air & fuel leak there, It would explain why it has a fair bit of fuel oil in the power head tray. Took the pump apart & the diapragham appears to have gone soft with age.
It turns out that the same mikuni fuel pump is also used on Rotax engines as used on microlight aircraft & hovercraft.
Interesting little device that operates on crankcase vacumn & pressure varying on demand with engine revs,
Also has the wrong spark plug in it.
Hoping fixing these will sort it!
 
Keith 66 said:
.
Interesting little device that operates on crankcase vacumn & pressure varying on demand with engine revs,
Click to expand...
That's how the fuel pumps on 2 strokes usually work.
I hope you have made a note of how it was assembled. Sometimes it can be fiendishly difficult to figure out if you havent.
 
This one is a small rectangular block with lid, rubber gasket, diapragm, card gasket & pump lid in that order, it only goes together one way which is good! Fuel pipes are all new replaced last year.
 
For some reason I have always had Johnsons, 2 x johnson 4 hp. I still have a johnson 4.5hp and a johnson 15hp. All two stroke . The only trouble with Johnson is they are a bit noisy and all have a rattle. They do the job though. I am comparing the noise to Yamaha. I have two 2 hp and 1x 9.5hp also two stroke but much quieter engines.. Johnsons are normally fairly easy to fix so best of luck.
 
Sorry thread drift.
I bought a Johnson 4hp 2T twin as a project and got it going OK. Only a mist of water as exhaust. Told this is about normal . Any thoughts or are all Johnsons like this.
TIA
 
Fuel pump rebuild kit fitted £12.50 from Spellfame Karting, new hose stub from crankcase to pump ran it tonight & wouldnt start, then noticed i had the pump on upside down so its pumping the wrong way. Remounted it & started easily. Now find that whatever you do it will only run with the choke on full. Push the choke in & engine dies.
Poxy thing is getting to me now. Does anyone know where i can get a manual? Only ones i can find are for 4 strokes or loads of money.
 
Keith 66 said:
Fuel pump rebuild kit fitted £12.50 from Spellfame Karting, new hose stub from crankcase to pump ran it tonight & wouldnt start, then noticed i had the pump on upside down so its pumping the wrong way. Remounted it & started easily. Now find that whatever you do it will only run with the choke on full. Push the choke in & engine dies.
Poxy thing is getting to me now. Does anyone know where i can get a manual? Only ones i can find are for 4 strokes or loads of money.
Click to expand...

Again, reckon you know more than me, but, isn't running only full choke a sign of a blocked jet?
 
Keith 66 said:
Fuel pump rebuild kit fitted £12.50 from Spellfame Karting, new hose stub from crankcase to pump ran it tonight & wouldnt start, then noticed i had the pump on upside down so its pumping the wrong way. Remounted it & started easily. Now find that whatever you do it will only run with the choke on full. Push the choke in & engine dies.
Poxy thing is getting to me now. Does anyone know where i can get a manual? Only ones i can find are for 4 strokes or loads of money.
Click to expand...
The operators guide is availble from Outboardbooks.com but not the workshop manual.
.
 
Mark-1 said:
Again, reckon you know more than me, but, isn't running only full choke a sign of a blocked jet?
Click to expand...

And upon stripping the carb again i found that yes the central fixed jet tube had several holes partially blocked with varnish plus another blocked completely. That was stripped & cleaned a year ago but sat since. It would seem that long periods of inactivity isnt good for it! All back together now & no reason it should not run!
Going to give it a try tomorrow but will see how it likes super unleaded for a change.
 
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