jay_merrill
Vice Admiral
- Joined
- Dec 5, 2007
- Messages
- 5,653
In another thread, I described a 1974 Evinrude 85hp motor that I picked up "on the cheap." I've had it for a few months, but just got around to working on it. The first problem that I ran into, was very low compression - about 30 psi on all four cylinders.
A couple of the very knowledgeable guys suggested stuck rings, so I applied PB Blaster directly into the cylinders multiple times, over a three day period. I also ran a can of BRP Engine Tuner through the motor, in two different applications. This was done by shooting the stuff down the carb throats, while spiining the motor via the starter, and by direct application through the spark plugs holes.
I now have 110 psi on cylinders 2 through 4, but only 90 psi on cylinder 1. We talk about the 10% differential rule a lot, but since I can probably get this motor going for very little money, I guess I am considering just "going for it."
So, my question is, "just how big a deal, is a 20 psi difference in one cylinder likely to be, given that none of the numbers are extremely low and three are actually pretty good?" I guess I expect a little roughness, but what else might I expect?
???
A couple of the very knowledgeable guys suggested stuck rings, so I applied PB Blaster directly into the cylinders multiple times, over a three day period. I also ran a can of BRP Engine Tuner through the motor, in two different applications. This was done by shooting the stuff down the carb throats, while spiining the motor via the starter, and by direct application through the spark plugs holes.
I now have 110 psi on cylinders 2 through 4, but only 90 psi on cylinder 1. We talk about the 10% differential rule a lot, but since I can probably get this motor going for very little money, I guess I am considering just "going for it."
So, my question is, "just how big a deal, is a 20 psi difference in one cylinder likely to be, given that none of the numbers are extremely low and three are actually pretty good?" I guess I expect a little roughness, but what else might I expect?
???
