94 25hp johnson please help.

W

wcgreer

Seaman Apprentice
Joined
May 26, 2012
Messages
34
I bought a john boat a few weeks back and this motor ran good and now it is popping like a backfire. I would normally think this is timing but im new to outboard world. It does run and i put new plug in, checked compression it was 115 on both. It doesnt wait to start popping as if something was overheating it does it immediately after starting cold. Can anyone please help me with some ideas of what to do.:confused:
 
D

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 94 25hp johnson please help.

Does it stop when the engine warms up? Open the low speed needle a 1/4 turn and see if it helps.
 
W

wcgreer

Seaman Apprentice
Joined
May 26, 2012
Messages
34
Re: 94 25hp johnson please help.

it does it constantly. i let it runs with muffs and get warm and adjusted idle but nothing helped. the more throttle i give the more it pops. is it possible that the timing is off?
 
D

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 94 25hp johnson please help.

I was talking about the low speed needle adjustment, not the idle.
 
W

wcgreer

Seaman Apprentice
Joined
May 26, 2012
Messages
34
Re: 94 25hp johnson please help.

sorry im not familiar with which screw that is. There is a tiny screw in the front of the carb and a screw with a spring on the left side of the carb.
 
fireman57

fireman57

Captain
Joined
Aug 24, 2004
Messages
3,811
Re: 94 25hp johnson please help.

make sure your plug wires aren't reversed.
 
W

wcgreer

Seaman Apprentice
Joined
May 26, 2012
Messages
34
Re: 94 25hp johnson please help.

Thanks for the diagram, I backed it out and it still was popping. and there are two coils with very short plug wires so they cannot be reversed. I am going to purchase a spark plug tester tommorow to check the spark. I read on the forum that if my spark doesnt jump 7/16'' than it is too weak. Does that sound like a something that may be a problem. Would a short video of it running help you help me?
 
D

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 94 25hp johnson please help.

A short video would be great.
 
H

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: 94 25hp johnson please help.

Popping on muffs is normal as you lack back-pressure and the engine will run lean. Put the lower unit in a barrel with water min 3" above the split between gear-case and leg and test.
 
W

wcgreer

Seaman Apprentice
Joined
May 26, 2012
Messages
34
Re: 94 25hp johnson please help.

I put the motor in a big plastic barrel that i use for my other boat and i noticed there was not much water coming out of the exhaust holes or the hose that is on the top of motor. I pulled the lower unit apart and the water pump housing was partially melted. I will order new parts this evening. I will fix and post a video of it running. Thanks for the help so far.

I bought the spark checker and the spark jumped 3/4'' on both coils.
 
You must log in or register to reply here.
Top