no power at full throtle

[imported_G-MAN]

i have a 1973 johnson 50 horse motor, at full throtle it boggs down,but at an idle in gear i can hit throtle by hand and i get full throtle.and if i disconnect the timing advance linkage and push throtle foward it run fine motor modle #e3824507 searial#50esl73r.motor was just rebuilt last year before i bought it,,any help ?

 

[jtexas]

Re: no power at full throtle

"at an idle in gear i can hit throttle by hand"...is that with the boat in the water, or on the muffs? Don't rev it that high on the muffs - you risk "runaway" in which the key nor cutoff switch nor pulling spark plug wires would stop it - it might tear itself up before you get it shut off.

fouled carbs will idle and rev fine but it'll bog when you put a load on it.

Funny that it will rev up without advancing the spark...its a mystery to me.

 

[imported_G-MAN]

Re: no power at full throtle

"at an idle in gear i can hit throttle by hand"...is that with the boat in the water, or on the muffs? Don't rev it that high on the muffs - you risk "runaway" in which the key nor cutoff switch nor pulling spark plug wires would stop it - it might tear itself up before you get it shut off.

fouled carbs will idle and rev fine but it'll bog when you put a load on it.

Funny that it will rev up without advancing the spark...its a mystery to me.

 

[imported_G-MAN]

Re: no power at full throtle

thats with the boat in the water,carbs are new,and i have had them off and inspected them and they look fine one person at works says maybe the gap on the timing trigger may be off,its set at .o20 as to instructions with the new trigger

 

[jtexas]

Re: no power at full throtle

sorry, I must have misunderstood your symptoms -

By "bogging" you mean it starts to rev up, but can't, as if it were still tied to the dock or something, so it dies? That would suggest fuel delivery problem.

Or, if you mean it just shuts off when you throttle up, like if somebody hit the kill switch? that's more consistent with electrical/ignition problem.

"in gear I can hit the throttle by hand" - I thought you meant operating the throttle linkage on the motor instead of pushing the throttle control lever at the helm. The boat runs wIthout bogging down when you do this? Or did you mean in neutral?

And with the timing advance linkage disconnected, the boat runs full speed, without bogging?

A shop manual would be an excellent investment if you plan to work on this motor yourself...factory manuals are available at marineengine.com and kencook.com.

Hang in there - somebody will jump in with an answer...

and btw, welcome to iboats!

 

[imported_G-MAN]

Re: no power at full throtle

sorry, I must have misunderstood your symptoms -

By "bogging" you mean it starts to rev up, but can't, as if it were still tied to the dock or something, so it dies? That would suggest fuel delivery problem.

Or, if you mean it just shuts off when you throttle up, like if somebody hit the kill switch? that's more consistent with electrical/ignition problem.

"in gear I can hit the throttle by hand" - I thought you meant operating the throttle linkage on the motor instead of pushing the throttle control lever at the helm. The boat runs wIthout bogging down when you do this? Or did you mean in neutral?

And with the timing advance linkage disconnected, the boat runs full speed, without bogging?

A shop manual would be an excellent investment if you plan to work on this motor yourself...factory manuals are available at marineengine.com and kencook.com.

Hang in there - somebody will jump in with an answer...

and btw, welcome to iboats!

 

[blackhawkdc]

Re: no power at full throtle

I had a similar problem with my 1971 Johnson 50 horse twin. Went through the carbs, new fuel pump, new coils. Ended up being that it had a bad CDi ignition unit. The engine would idle fine and rev up ok with muffs on, but the moment I put it in the water with a load, it'd just bog out. Turns out I had weak spark on one of the cylindars. so if your carbs are all good and the fuel pump is good, you might look into that CDI ignition unit.

Hope this helps and let us know when you get it fixed!

Seth Petro