Thread: Scary low compression

take it to the shop and have them plug it up for a diagnostic. amazing what computers will tell you these days.

Had my good buddy do a routine service this summer on my boat. Lucky for me he has the computer program to plug up and get the diagnostic for Yamaha engines. after plugging it up and turning it on, i got an error message saying "thermostat stuck in on position" causing my motor to burn cold. what does that mean? I dont know. But if it was not identified, it would have caused a catastrophic engine issue several months or even years down the road.

Spend the little extra cash and get that done and be done with it.

My 2002 my not have the computer link, will see


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Originally Posted by brettw

Sure
It's made in China


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could you post a picture of the gauge ?

[QUOTE=brettw;3308435]Just did a cold engine compression test on my Yamaha F50 ,2002,
Results were frightening
Cylinder 1 55
2. 56
3. 55
4. 63

Added oil to cylinders
1 64
2. 56
3. 60
4. 66

Should be 110-120?

Symptoms, mostly hard to start
Easier to start out of water
Weak hole shot
Runs well once going

Ideas ?
Thanks


Sounds worn out to me. Just because the compression is so close to each other. I would think the oil would had gotten you higher.
Have the valves been adjusted? Should be about every 100 hrs according to manual.
If you are close to Lake Wylie I have a Mac Tool compression tester I can check it for you if needed.
How many hrs do you think is on the engine?
Also has it been using any oil lately ?. If it were a 2 stroke, which it is not the first thing I would check is the exhaust to see if it is stopped up.
However if it is using oil there is still the possibility of the exhaust being stopped up.
I just not sure how the exhaust would run the compression down. Just saying.
Also. Has the timing belt been change, if has it run right since?

motor wouldnt start with those numbers...at least not with out ether, I would verify the gauge works properly, then recheck with throttle plates open.

[QUOTE=Poorman;3308646]

Originally Posted by brettw

Just did a cold engine compression test on my Yamaha F50 ,2002,
Results were frightening
Cylinder 1 55
2. 56
3. 55
4. 63

Added oil to cylinders
1 64
2. 56
3. 60
4. 66

Should be 110-120?

Symptoms, mostly hard to start
Easier to start out of water
Weak hole shot
Runs well once going

Ideas ?
Thanks


Sounds worn out to me. Just because the compression is so close to each other. I would think the oil would had gotten you higher.
Have the valves been adjusted? Should be about every 100 hrs according to manual.
If you are close to Lake Wylie I have a Mac Tool compression tester I can check it for you if needed.
How many hrs do you think is on the engine?
Also has it been using any oil lately ?. If it were a 2 stroke, which it is not the first thing I would check is the exhaust to see if it is stopped up.
However if it is using oil there is still the possibility of the exhaust being stopped up.
I just not sure how the exhaust would run the compression down. Just saying.
Also. Has the timing belt been change, if has it run right since?

Valve adjustment is a good idea
No idea of the hours on motor
Not using oil
Timing belt has not been changed
Timing may need adjustment


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Originally Posted by pete

Seafoam is great for a quick clean, but its actually recommended you not use seafoam for the newer 4 stroke engines.

Ordered some ringfree


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Thanks to everyone that chimed in on this.
I warmed up the motor, WOT, rechecked it today
All 4 read between 115 &125
Thanks again, now I know how to do it, plus I'll start adding ring free slowly to the system


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