1977 55hp johnson

[patthelee]

help i've got an old 55 hp that just got the head refaced and put a new head gasket on . put it back in the water and it ran just like it did before the new head gasket. it runs for great for about 3 -5 mins then it losses all power and just crawls along, i thought it may be getting water in the cylinders but cant tell. would a compression test tell me so? and if there was water in the fuel would it show up on the plugs? this old girl runs fine in the tub or one the muffs. but when i put it in the water it dose the same thing
the other train of thought was a dodgy coil when it heats up maybe it brakes down. help .

 

[sloopjimd]

Re: 1977 55hp johnson

you schould do a compression test then due a cylinder leak down test. Have you cleaned and rebuilt your carb or carbs? It may only be somthing floating in the float bowl jamming things up.
Good luck

 

[ondarvr]

Re: 1977 55hp johnson

Running good for a few minutes and then losing all power doesn?t indicate a compression issue, it would either be electrical or fuel related.

You need to check it when it loses power to see if its getting spark to both plugs. Its very common for the coils to go bad, they may work at first, but as they heat up they fail.

If there's good spark then clean the carbs and check the fuel lines.



Did you check to see if the vent on the gas tank is closed or plugged

 

[patthelee]

Re: 1977 55hp johnson

hi, thanks for the input. think i have found the problem, I got home late last night and run the motor in the tub, i took off the lead to the bottom plug and the motor died nealy straight away but if i took the top one off it would still run but not as smooth, the coil for the top cylinder is arcing from the core to the metal plates on the coil itself. so i got on to my local omc guy "gota love a bloke who lives in his work shop" and he has a set for $50 bucks they come off a motor that he was rebuilding for a bloke that didn't come back 12months ago. he said they were in great nick. so im off to get them this arvo &
out on the ocean friday night.