Johnson 5 HP 2 stroke doesn't give its full power in gear

[Knientje]

A friend of mine has a Johnson 5 HP 2 stroke outboard (about 30 years old). It has been revised, but it still has the same troubles.<br />It does start (not easily, but it starts and it keeps running), but when you open the throttle fully, it doesn't give all the power it has (It makes less rpm than it should). In neutral with the throttle full open it sounds like it gives full power, but if you have the throttle full open in forward or reverse it doesn't give the power it should give. Is this a common Johnson problem? (Erm the language barrier makes it a bit difficult to explain it in good english<br /> but I hope/think someone understands ) oh and what is the mix proportion?

 

[Knientje]

Re: Johnson 5 HP 2 stroke doesn't give its full power in gear

I think I found out the problem. Today I was trying to start it, I don't know the engine very well, because I bought it from my friend. So I need to become familiar with it. But before starting I was pumping some fuel on the carb, I pumped too much so the carb flooded. But while trying to start it one of the clinders blew the spark plug out because the engine backfired. And the leaked fuel caught fire. . Fortunately not my boat or the engine itself. So then I found out the spark plug hole was bored up, but not in a very professional way and they cut new screw thread in the hole and put the spark plug in (well they attempted to )<br />So I have an idea that the engine sucked false air via the spark plug hole. Cause the screw thread has totally gone. Now I removed the cylinder head. And go it to bring to someone who can weld aluminium and alloys to weld the spark plug holes up, so the wholes become smaller again and we can cut the original size for the screw thread of the

 

[Knientje]

Re: Johnson 5 HP 2 stroke doesn't give its full power in gear

spark plug. Another question: Because I removed the cylinder head. I need a new head gasket. Does anyone know what a reasonable price for a new head gasket is for this engine? Since the inteoduction of the Euro they dare to ask unreasonable high prices here (If you fall for it) . And a correction. The engine is a 5.5 HP 2 stroke Johnson. Model CD20C <br />Serial Number B100048

 

[Paul Moir]

Re: Johnson 5 HP 2 stroke doesn't give its full power in gear

There's a much simpler solution to the sparkplug problem. You cut a _larger_ thread through the spark plug holes and put in a bushing that reduces the size back to a 14mm spark plug thread. Over here they're called 'heli-coils', they're must be something similiar over on your side. Ask an auto mechanic.<br />Also - you said you pumped the primer bulb and fuel ran out the carburator. That indicates that the needle valve inside the carburator is worn out and leaking. It will cause your engine to run too rich. The solution is replacement, since parts are still available.<br />Finally, if your problem doesn't go away, take a look at your ignition coils. The insulation on old ones cracks from age. This causes the coil to arc over at higher rpms, so you loose spark in one or the other cylinder at higher rpms. The spark often looks fine when you test it with the pull starter.<br />Good luck!

 

[Paul Moir]

Re: Johnson 5 HP 2 stroke doesn't give its full power in gear

That's a '63 engine, by the way. Your head gasket can be foundhere. They're a little slow, but they still export. Part 18-2961 is your head gasket. Part 18-7043 is your carburator overhaul kit.

 

[Knientje]

Re: Johnson 5 HP 2 stroke doesn't give its full power in gear

They are called heli coils here, too, but because that already happened once there ain't no oversized helicoil. (the spark plug that blew out was already in a heli coil) And I don't have to leave it for the price. the welding is more expensive,but still affordable. but it's the only solution. I'll check the carb though. I have friends with a car repair shop and they advised me to weld up the sparkplug hole. Thanks for the info anyway Paul