1999 Johnson 25HP issues.

[goodtimes]

Hello,

I was having issues with water in the top cylinder. I pulled the head and noticed that the previous mech that changed the head gasket did a very poor job on making sure the head was even. I took the head to a shop and used their sandpaper board and made sure the head was even. Torqued the head gasket correctly and it resolved the water issue.

The only problem now is when I pull the bottom plug at idle it won't run on only top cylinder. if i unplug the top, the bottom runs great.

Compression on both cylinders are around 100psi.

 

[jbjennings]

Re: 1999 Johnson 25HP issues.

It may run great on the muffs but guaranteed it won't even plane your boat at the lake. You've got bad spark on the top cylinder. could be a bad coil (not all that expens. ) or a bad powerpack. I'd first check the spark to see if it will jump a 1/4 inch gap. If not, I'd swap coils and see if the problem follows the suspect coil. If so, replace your bad coil. Easy fix, she'll run great.
They all run good on the muffs or in the tank, but hit the throttle at the lake and the truth is revealed. I hope it's just the coil.
Good luck,
JBJ

 

[goodtimes]

Re: 1999 Johnson 25HP issues.

Tried flipping the coils, replacing the power pack and changed the spark plugs. Still same issue. Checked the compression again and both around 100PSI. I did notice some exhaust or unburned fumes coming out when i removed the top spark plug but none from the bottom and the top spark plug was not as wet as the bottom.

I recently changed the exhaust gaskets also.

What else could it be from?

 

[The-Machinist]

Re: 1999 Johnson 25HP issues.

Does your motor have 2 carbs? If so, maybe the top carb is the suspect.
If not, maybe the reeds?

 

[The-Machinist]

Re: 1999 Johnson 25HP issues.

100 psi is the point at which I decide to rebuild a motor(if not sooner). It really is at the very bottom end of "acceptable". It is going to be very hard to get this motor to run right with those numbers.

 

[goodtimes]

Re: 1999 Johnson 25HP issues.

Only one carb. How would I check the reeds?

 

[The-Machinist]

Re: 1999 Johnson 25HP issues.

Usually, I just put my hand in front of the running carb. If I get fuel spray on my hand then I go after the reeds.

 

[goodtimes]

Re: 1999 Johnson 25HP issues.

Thanks for your help.

I did notice fuel spitting out from the carb. Is it simple to replace the reeds? Would I need special tools?

 

[The-Machinist]

Re: 1999 Johnson 25HP issues.

Should'nt need any "special" tools. But remember, You are still putting another decent chunk of money in a pretty worn powerhead.