helpppp 1978 70hp johnson seahorse will not run once in the water

[juross]

hi i am not a boat mechanic but have worked on everything else this is my first boat anyways i just tore apart the carbs cleaned them made sure they did not need rebuilt or have anything in them just replaced impeller too well i put muffs on it and throttled in reverse and forward it did fine well as soon as i took it off the trailer in the lake it doesnt wanna run right and as soon as i put in into forward or reverse it dies so then i decided to take the top off and and throttle it with my hand while my buddy put it in gear and it went but it only went 12 mph or so and sounded like it was idling low can anyone tell me how to fix this im in desperate need thanks in advance

 

[juross]

Re: helpppp 1978 70hp johnson seahorse will not run once in the water

is anyone on here able to help me

 

[Chinewalker]

Re: helpppp 1978 70hp johnson seahorse will not run once in the water

Spark checked? Compression checked? Carbs rebuilt with ethanol resistant gaskets? Sounds like you're only running on one or two cylinders.

 

[eavega]

Re: helpppp 1978 70hp johnson seahorse will not run once in the water

Do you have a Tachometer on the motor? You need to know what speed your motor is running when its only giving you 12 MPH. The "Audio Tachometer" is notoriously unreliable

 

[juross]

Re: helpppp 1978 70hp johnson seahorse will not run once in the water

no i do not have a tach at all. what all should i do? yesterday i cleaned out the fuel pump and everyfuel line was good im at a loss here

 

[eavega]

Re: helpppp 1978 70hp johnson seahorse will not run once in the water

As Chinewalker implied, check spark with an air-gap spark tester. It should be able to jump a 7/16" gap with a good visible blue bolt. All three cylinders. After that, check compression on all three cylinders with a compression tester. Next verify that the fuel pump is, in fact, pumping fuel and isn't sucking air somewhere. Verify that the carburetor bowls are filling and the needle valve is not sticking closed. If your motor idles, try doing a cylinder drop test, where you pull the plug wire on one cylinder while the motor is running. If it starts running rough or stalls out, that cylinder is running. If there is no change, then that cylinder is NOT running. It is either missing fuel, compression or spark.


Rgds

 

[juross]

Re: helpppp 1978 70hp johnson seahorse will not run once in the water

i figured it out its getting way to much fuel i believe i just have to adjust the floats im getting good spark 2 of my cylinders was at 125 and the 3rd cylinders compression was 123 so i got in out on the water and put a fuel reg. switch in and when i shut the fuel almost all the way off it ran like a top around 45 mph