Fixing compresion Johnson 40hp

[ThunderAce]

Hello everyone

I have a
Johnson 40hp VRO 1988 (J40ELCCS)

I need the parts to fix the compression on this one.
Anyone that can help.......

As I was told I will need new piston rings, and I will need to "grind" cylinders.
But I was also told that it´s not all.

??????????

[boats.net]

The amount of damage to the cylinder determines the amount of work required. If the rings are the only worn part, then you can just hone the cylinders and replace the rings and gaskets.

[ThunderAce]

What about the seal located on the crankshaft, is´t that one also the one part that can cause bad compression.

I hope that I´m talking abour the right seal.

[boats.net]

compression is not determined by any seal, however if you have a blown head gasket that can cause low compression.

[Rebel Sympathy]

Originally Posted by ThunderAce

Hello everyone

I have a
Johnson 40hp VRO 1988 (J40ELCCS)

I need the parts to fix the compression on this one.
Anyone that can help.......

As I was told I will need new piston rings, and I will need to "grind" cylinders.
But I was also told that it´s not all.

??????????

You probably have scored cylinder walls, either from overheating or from a lack of oil - or a lean fuel condition. Most likely, you are going to have to bore your cylinder - or cylinders - .020" to .030" oversize- and then buy new oversize piston - or pistons - to match the re-bore(s). I.e., you are going to need to rebuild your motor...... Not cheap to do.

If you do rebuild your motor, by all means, rebuild your carbs, replace your VRO, replace your water pump and replace your thermostats. Also, it won't hurt at all to go up at least one (or two) jet sizes in your twin carbs to compensate for the larger displacement fuel consumption demands created by the overbore.

I replace my VR0 pump every seven years, whether it needs it or not. I also add a 100:1 ratio of oil directly to the gasoline in the tank - about 1.5 oz of oil per gallon of gas. That is my safety valve, in case the fuel/oil pump fails. Much cheaper than an engine rebuild and most likely will save the powerhead unless I am at full ignition advance at Wide Open Throttle (WOT) when a 100% complete Fuel/Oil pump failure occurs......

Three things killed off OMC:
1) High ring groove piston design, 1979 and up through the decade of the 1980's on Crossflow V-4 and V-6 motors.
2) The VRO (fuel/oil pump) early lack of reliability of the 1980's.
3) The ill-fated FICHT 2-stroke fuel injected motors of 1998-2001. (By then the company was financially weak and you can't build reliable motors when you only have 57-cents in your budget to spend on an exhaust temp sensor.....)