Fishing Michigan
New member
I have a 60 HP 1969 Johnson Hydroelectric Outboard 3 Stroke Motor. All carbs have been rebuilt, distributor is new, all spark plugs are new, fuel filter is clean, and is in relatively good working order except for this one issue.
I had a 13"x7" prop on and my top speed before the sputter was about 12 to 15 mph. I changed it to a 13"x9" prop and my speed went up to about 20 to 25 mph before it would start to sputter again. (both are alluminum props)
After I reach a certain speed, and still have plenty of throttle left, I try to go faster, and all the happens is the RPM's will go higher, the motor will sputter, and the boat will surge in unison with the sputtering, like it wants to keep up, but it just can't. It's almost like it's starving for fuel, but the fuel supply isn't restricted in any way.
I've been told it could be my prop, I need a deeper pitch. That it has something to do with the RPM's feeding back causing the sputtering, or some kind of module on the side of the motor that has a ton of wires coming out of it.
My buddy, who is a marine mechanic, just not on engines this old, did do a basic diagnostics of all electrical, out drive, etc. All to be in working order.
I just read about how to check a prop for splipping, so I will do that test as well, as I thought that was my first propblem, which is why I changed them.
Any advice or help on this matter would be grateful. I am willing to take it in to a reputable marine shop who works on these types of motors, ie: year etc. but am hoping to find a cheaper answer.
I had a 13"x7" prop on and my top speed before the sputter was about 12 to 15 mph. I changed it to a 13"x9" prop and my speed went up to about 20 to 25 mph before it would start to sputter again. (both are alluminum props)
After I reach a certain speed, and still have plenty of throttle left, I try to go faster, and all the happens is the RPM's will go higher, the motor will sputter, and the boat will surge in unison with the sputtering, like it wants to keep up, but it just can't. It's almost like it's starving for fuel, but the fuel supply isn't restricted in any way.
I've been told it could be my prop, I need a deeper pitch. That it has something to do with the RPM's feeding back causing the sputtering, or some kind of module on the side of the motor that has a ton of wires coming out of it.
My buddy, who is a marine mechanic, just not on engines this old, did do a basic diagnostics of all electrical, out drive, etc. All to be in working order.
I just read about how to check a prop for splipping, so I will do that test as well, as I thought that was my first propblem, which is why I changed them.
Any advice or help on this matter would be grateful. I am willing to take it in to a reputable marine shop who works on these types of motors, ie: year etc. but am hoping to find a cheaper answer.