formulajoe57
Cadet
- Joined
- Jul 17, 2006
- Messages
- 8
Hi everyone and thanks for reading my post!
I have a 1998 Johnson 115 SPL 90 degree V. Its on a Glastron 19? with a stiletto 13.25 x 19. It was purchased in August of 1999. We use it primarily at a ?no wake? lake and it puts around about 25 hours a year (about 1300 RPMS) and goes fast about 4 hours a year. Its never had any issues until about two years ago it began to miss and idle rough. I only used the Johnson synthetic 2 cycle oil in the VRO tank. Now its getting to the point that it wouldn?t idle for more than about a minute before stalling.
What ive done so far (today): new fuel line from tank to motor and new priming bulb, new inline fuel filter, new coil packs, tested the power pack and it was fine, rebuilt the carbs, new spark plugs and wires and it still misses at idle the exact same as before I did all this.
I just did a compression reading and found 3 cylinders are 95 and 1 is only 83. That new spark plug was already carboned up very shortly after running it. I removed the head and the low cylinder contained much more carbon than the good one. Im assuming this low cylinder with all the carbon is so carboned because it is running rich because it doesn?t have as much air during combustion. (see picture)
Question 1: So is the carbon point to the cause of the low compression or is it a result of low compression
Question 2: Is it likely that the rings need replaced or is there something else causing this low compression? What else could cause low compression?
Question 3: If I do need to replace the rings, the cylinders don?t appear to be scored or any marks, do I have to do anything but hone the cylinders and replace the rings using the same piston?
Question 4: How can I find the cause of this low compression cylinder so it doesn?t happen again?
Question 5: Are the other readings of 95 low or about right?
Question 6: Why would this motor fail so soon with so little hours on it?
Thankyou for any help!
Joe
I have a 1998 Johnson 115 SPL 90 degree V. Its on a Glastron 19? with a stiletto 13.25 x 19. It was purchased in August of 1999. We use it primarily at a ?no wake? lake and it puts around about 25 hours a year (about 1300 RPMS) and goes fast about 4 hours a year. Its never had any issues until about two years ago it began to miss and idle rough. I only used the Johnson synthetic 2 cycle oil in the VRO tank. Now its getting to the point that it wouldn?t idle for more than about a minute before stalling.
What ive done so far (today): new fuel line from tank to motor and new priming bulb, new inline fuel filter, new coil packs, tested the power pack and it was fine, rebuilt the carbs, new spark plugs and wires and it still misses at idle the exact same as before I did all this.
I just did a compression reading and found 3 cylinders are 95 and 1 is only 83. That new spark plug was already carboned up very shortly after running it. I removed the head and the low cylinder contained much more carbon than the good one. Im assuming this low cylinder with all the carbon is so carboned because it is running rich because it doesn?t have as much air during combustion. (see picture)
Question 1: So is the carbon point to the cause of the low compression or is it a result of low compression
Question 2: Is it likely that the rings need replaced or is there something else causing this low compression? What else could cause low compression?
Question 3: If I do need to replace the rings, the cylinders don?t appear to be scored or any marks, do I have to do anything but hone the cylinders and replace the rings using the same piston?
Question 4: How can I find the cause of this low compression cylinder so it doesn?t happen again?
Question 5: Are the other readings of 95 low or about right?
Question 6: Why would this motor fail so soon with so little hours on it?
Thankyou for any help!
Joe
Seriously, they like to be run at a high RPM most of the time, and the motor is really carboned up. What I would do is put new head gaskets on, and do a thorough decarb procedure on the motor (link in the "Top Secret" post at the top of the forum). I'd also check to make sure the thermostats are functioning properly. I'd decarb sooner than later, because if the ring slots get too gunked up, they can stick and break off a ring.