Logo
FULL SITE MENU

Johnson 25 HP 3 Cylinder Problems

Y

YL380

New member
Hi all,
I have been lurking here for years and solved all kinds of issues from the knowledge here. I finally have something going on that has stumped me.


The motor in discussion here is a 1998 Johnson 25 HP 3 Cylinder J25KLECA.

This was on the back of a boat that I just purchased.

I can get the motor to fire up, but it will only start by using the primer system and dies shortly after. It will not idle, but I can rev it up for a second or two before it cuts out.

So far I have:

1. Changed inline fuel filter
2. Rebuilt and cleaned all carbs
3. Rebuilt the dual fuel pumps
4. Removed the automatic oiling system to ensure I was getting mixed fuel and oil to the motor
5. Tried running off a different fuel tank

Here is where it gets even more strange, I did a compression check and all three cylinders are exactly 60 lbs on the dot and verified with two different tools. I removed the head and inspected the cylinder walls and while the center had a tiny section .5" where it looks like there is some scoring they all look factory perfect with cross hatching still in place.

I then replaced the o-rings and sealed everything up exactly the way that it came from the factory. I tried pouring some marvel mystery oil in there to see if I could free up the rings, but I feel like I need to get the thing running long enough to create some heat in the motor and possibly free up the rings?

Any ideas at all? All input is greatly appreciated.
 
YL380, there is no replacement for this test,A fully charged battery,plugs removed,200-300 rpms should do it
 
Last edited:
daselbee said:
60 psi is way too low.
Click to expand...

This is true, however I haven't been able to run the motor for any length of time to see if the rings are stuck or not. Before I got it, it probably hasn't been run in 3 years.

Even so, with that much compression it should still run. Also how would it be possible for there to be a problem across all three cylinders identically. This combined with the cylinder walls looking like new makes me believe I have some stuck rings.

There is some sort of fuel issue going on here that I just can't figure out. Maybe the leaf valves?
 
The high speed jets I was talking about are in the bottom of the float bowls. Did you have them out ??
 
Back
Top