112hp Johnson

[winterhawk78]

Boat a 94 Sprint has a 112hp Johnson on it. Has some idling cranking, idling, running issues.....but not all the time. When I got it there were two coil or power pack wires that the wires had been pulled out of the boot and taped back up along with one spark plug wire. I have repaired these issues. The boat still isn't right, this past weekend I took it out, dropped it in the water cranked pulled to the dock roped off pulled trailer out and off to my spot. Ran fine, got up on plane like I think it should. Fished for an hour went to move spots, took a few cranks to get it going but did. This time when I would push the lever down for more throttle it booged and died. Did this a few times. Finally it caught and to the dock I went. Got the trailer in the water and when I got back to the boat to crank it, it would not crank, took a while and when it did ever time I went to throttle up it would die. Finally I cranked it and just pushed it down quickly and it stayed running. There has been other times where I have been idling along and when I went to try to open it up it would just bog down and die. Anyone have any ideas on what I can try or what to do. I am a complete newbie to be a boat owner.

 

[ondarvr]

You will need to do some detective work.

Check compression, this is always the first thing done on these motors.

​Make sure it has spark, especially when it's acting up.

​Try squeezing the primer bulb when it's dying, this will let you know if it's an air leak or fuel pump issue.

​When you say crank, do you mean turning the key and having the starter spin the motor, or it actually starting? Some people use the term cranking for the motor starting and it confuses the conversation.

 

[winterhawk78]

You will need to do some detective work.

Check compression, this is always the first thing done on these motors.

​Make sure it has spark, especially when it's acting up.

​Try squeezing the primer bulb when it's dying, this will let you know if it's an air leak or fuel pump issue.

​When you say crank, do you mean turning the key and having the starter spin the motor, or it actually starting? Some people use the term cranking for the motor starting and it confuses the conversation.

How would I go about checking compression and if it has spark?

How do I know if by squeezing the bulb if its air or the fuel pump? Can you explain a little more on that too?

I meant turning the key, but also if i said it cranked that means the engine stayed running. I will do better at clarifying that in the future.

 

[interalian]

For compression test, remove all 4 spark plugs and ground the leads. Fit compression tester in each cylinder in order and crank the motor over watching the gauge. You should get maximum reading after 4-6 revolutions - watch the needle. Write down the number, reset the gauge and move to the next hole until you're done. Should be 100-120psi/hole with 15% variance maximum from highest to lowest.

Spark test: you should get a 7/16" bright blue snappy spark between the spark plug lead and ground. You'll need to rig something to make that gap, or use a store-bought air-gap tester that can be adjusted to 7/16"

If the reason the motor loses power is lack of fuel, pumping the primer ball makes up for a bad pump or air leaks between the tank and pump, allowing the motor to run WOT as normal.

 

[winterhawk78]

For compression test, remove all 4 spark plugs and ground the leads. Fit compression tester in each cylinder in order and crank the motor over watching the gauge. You should get maximum reading after 4-6 revolutions - watch the needle. Write down the number, reset the gauge and move to the next hole until you're done. Should be 100-120psi/hole with 15% variance maximum from highest to lowest.

Spark test: you should get a 7/16" bright blue snappy spark between the spark plug lead and ground. You'll need to rig something to make that gap, or use a store-bought air-gap tester that can be adjusted to 7/16"

If the reason the motor loses power is lack of fuel, pumping the primer ball makes up for a bad pump or air leaks between the tank and pump, allowing the motor to run WOT as normal.

Thanks I will work on getting these checked out.

First I need to buy or borrow a tester for checking the compression.

 

[ondarvr]

Auto part stores will frequently loan out, or rent tools like these.