jay_merrill
Vice Admiral
- Joined
- Dec 5, 2007
- Messages
- 5,653
Re: johnson controls
Try to run the '73 65hp in a barrell, not on muffs. You have no back pressure on the exhaust system and no resistence acting on the prop when running on muffs. Because of this, you could have a cylinder misfiring and never know it.
In addition to checking compressions on the motor, bring an inductive timing light and check each plug wire to see if the ignition is firing all the way through to the coils & spark plug wires. You could also bring a spark checking tool, so that you can go as far as checking the quaility of the spark to each plug.
Bring a large, flat head screwdriver, so that you can check the gear lube. Be on the lookout for signs of water intrusion and/or metal shavings in the oil.
If the motor is mechanically sound, the most likely area for problems is in the ignition. It is not uncommon to have to replace all three coils, the powerpack, the timer base and the stator. I would ask if any of those things have been replaced and when. If the powerpack has an aluminum casing, its an original part and will most likely not last long. Same with the timer base - if it is a metal part, its an original part. The new ones are plastic (usually blue) and are sealed units. Look for the usual in regard to ignition coils - cracks and are discoloration are signs that replacement will be soon needed, if not needed immediately.
All of this said, these are great motors if they are in good shape. I am extremely pleased with my 1972 Johnson 65hp motor.
Try to run the '73 65hp in a barrell, not on muffs. You have no back pressure on the exhaust system and no resistence acting on the prop when running on muffs. Because of this, you could have a cylinder misfiring and never know it.
In addition to checking compressions on the motor, bring an inductive timing light and check each plug wire to see if the ignition is firing all the way through to the coils & spark plug wires. You could also bring a spark checking tool, so that you can go as far as checking the quaility of the spark to each plug.
Bring a large, flat head screwdriver, so that you can check the gear lube. Be on the lookout for signs of water intrusion and/or metal shavings in the oil.
If the motor is mechanically sound, the most likely area for problems is in the ignition. It is not uncommon to have to replace all three coils, the powerpack, the timer base and the stator. I would ask if any of those things have been replaced and when. If the powerpack has an aluminum casing, its an original part and will most likely not last long. Same with the timer base - if it is a metal part, its an original part. The new ones are plastic (usually blue) and are sealed units. Look for the usual in regard to ignition coils - cracks and are discoloration are signs that replacement will be soon needed, if not needed immediately.
All of this said, these are great motors if they are in good shape. I am extremely pleased with my 1972 Johnson 65hp motor.
