Johnson 4hp stroke outboard help please

Philiz

Philiz

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Staffordshire Moorlands U.K.
www.shabiera.co.uk
A mate has one of these units 1994 vintage, keeps cutting out which i'm guessing is a carburation problem as it's been laid up for some time. My question is, how do you tell if it's pumping water okay? So far as i'm aware they don't have the usual tell-tale. The engine does seem to get a tad hot. Cheers in advance.


P.S. Title was supposed to say '2 stroke'
 
Last edited:
Philiz said:
A mate has one of these units 1994 vintage, keeps cutting out which i'm guessing is a carburation problem as it's been laid up for some time. My question is, how do you tell if it's pumping water okay? So far as i'm aware they don't have the usual tell-tale. The engine does seem to get a tad hot. Cheers in advance.


P.S. Title was supposed to say '2 stroke'
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No they dont have a tell tale but there should be some water blown out of the exhaust back pressure relief port on the back of the leg with the exhaust gas.


( Below the bottom steering pivot on the basic version I think. From under a small cover right at the top on the deluxe ( FNR gears) version.)


You should be able to touch any part of the engine and maintain finger contact briefly, except for the head adjacent to the spark plugs and the exhaust manifold cover plate.

If you cannot, or if there are signs of paint discolouration or if a splash of water sizzles and boils away it is overheating.
 
VicS said:
Kawasaki said:
They were 2 cylinders .. 87cc

I dont know if the later ones kept the reputation of earlier ones but some reckon that the older 4hp johnnyrudes were just about the best small outboards bar none
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Thought so Vic
Crackin motors
Got one to fix at the mo
Done all the stuff but it won't run for long underload
Fine in the 'Tub' but runs for a minute or two on the 'ding' then falters
Pull the choke and it re - lives, like they do
Stripped the carb to bits twice and done the 'usual'!
Found a seal/o ring that is a bit hard/'degraded' on one of the main jet passages but struggling to get a replacement
Tried Bill Higham
Might not be that though
Might be a blockage in another passageway
Gonna take the carb to me mates motorbike place
who has a strong /fine compressed air pump with a 'fine' strong air nozzle
imho- that's the prob most times!
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Thanks Guys, yes it's a twin cylinder, nuetral and forward gear only version. There is hot air coming from the vent at the back/top of the leg bot no water. It's a bit oily around there, I presume that's from the exhaust. Looks like I need to strip the leg off and check the impellor and water pipe etc. Engine shows no obvious signs of overheating, there doesn't feel a lot of compression but it starts and runs okay and I understand these engines are quite easy to spin over.

Kwackers, stop nicking me post! Sounds like your engine does the same as this one, dies after a few minutes running but re-starts no problem. Got to be fuel trouble I reckon, sound like the one you have is scrap, I'll give yer 20 quid fer it ;)
 
Phil

It is really best to change the impellor every year or two. They dryout and the vanes will breakoff. If the motor has been setting for some time with any fuel in the carb, you may need to clean the jets and bowl.
 
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