Minimum reference pressure is 101.5 psi at 68 degrees F.

Ideally, all cylinders will be within 10% of each other.

Thanks. I had a survey done today on a boat I am about to purchase and the surveyor was looking for the Yamaha compression ranges.

My 2011 f300 had 175 psi on all 6, cold, that was with 1,500 hrs.

why not have a leakdown test done?
faster and about 100% more accurate .
a leakdown test will find issues that a compression test simply cannot.

I wonder why the service manual does not provide any reference whatsoever to differential (aka leakdown) test values?

If someone has a motor that has 150 psi in all six cylinders, and the motor starts, idles and runs well, it meets Yamaha specifications so what is the purpose of a differential pressure test? Yes, one might then see that a piston ring leaks a bit in one cylinder, an exhaust valve leaks a bit in a different cylinder, and an intake valve leaks a bit in yet another cylinder, but so what?

If anyone already owns a perfectly good Yamaha, but a differential pressure test or direct pressure test discloses differences between cylinders, and there are no operational issues with the motor, are they going to open the motor up for an inspection? I doubt it.

No but if looking to buy a motor or just bought one it would be nice to know what kind of problems you have starting out and what to watch for in the near future or to find a different one to buy instead

Interesting thought process.

OK to own and operate a motor with low compression values whereas it is might not be OK to buy a motor that has better (but not perfect) compression values.

I do see using compression values as a tool to beat the seller up with in order to try and get a better price. Kind of like going around a boat, motor and trailer while picking fly shit from the pepper to hammer the poor seller with.

Funny how what we own and use is perfectly acceptable to us but if we were to consider buying it, it might not be acceptable. We live in houses that are not worthy of being sold. We only spruce them up when it comes time to selling them. We spend money to make them better but never get to enjoy the benefits from the money that is spent. Myself included.

I know,
I am guilty of this also.
I make sure to not fix everything on the house exterior just to be able to argue with the county tax people to try to get the taxes lowered.



If I was looking at 2 motors and one tested better than the other, I would be trying to buy the good one instead of the one showing some problems.

If I already owned one with problems showing up during testing , at least I would know that it needed a valve or ring job , etc. and the longer I run it the worse it will get.

So I may not want to run far out to sea if a known problem exists.

But for the people that have no clue what the test results mean, they just may run it until it fails and strands them in a difficult situation just like the tests never were done

This is what I got back from the survey this week:

Compression values (cold / 40*):

#1 173#
#2 169#
#3 162#
#4 165#
#6 169#

Leakdown:

#1 2%
#2 3%
#3 6%
#4 2%
#5 2%
#6 2%

Some of the ECU download data:


Note: This list shows current faults only.
Please check the history section for stored
faults that are currently not active.


*********************************
***** Run Time History *****
*********************************

0-1000 RPM: 61.4 Hrs
1000-2000 RPM: 16.8 Hrs
2000-3000 RPM: 2.3 Hrs
3000-4000 RPM: 11.4 Hrs
4000-5000 RPM: 15.4 Hrs
5000-6000 RPM: 4.8 Hrs
6000-7000 RPM: 0.0 Hrs

Total Run Time: 112.1 Hrs




*********************************
***** Operating History *****
*********************************
Available Diagnostic Record Parameters:
#1: Engine speed
#2: Battery voltage (12-16)
#3: Throttle position sensor
#4: Engine temperature (below 302)
#5: Intake pressure
#6: Oil pressure (below 842)
#7: Throttle request
#8: Shift position sensor

Time #1 #2 #3 #4 #5 #6 #7 #8
Min RPM V V °F kPa kPa % V
----- ----- ----- ----- ----- ----- ----- ----- -----
-1 650 14 0.61 142 38.1 444 0 2.5
-2 650 13.8 0.61 140 39.1 452 0 2.5
-3 600 13.9 0.61 138 39.1 459 0 2.5
-4 600 13.9 0.61 136 40.1 467 0 2.5
-5 600 14 0.61 133 40.6 479 0 2.5
-6 650 13.9 0.63 127 41.1 494 0 2.5
-7 750 13.8 0.66 109 43 513 0 2.5
-8 850 13.8 0.68 80.6 42.5 536 0 2.5
-9 600 13.9 0.61 149 37.6 322 0 2.52
-10 650 14 0.61 149 38.1 329 0 2.52
-11 650 13.9 0.61 149 37.6 329 0 2.52
-12 600 13.8 0.61 147 37.6 329 0 2.52
-13 650 13.9 0.61 147 38.1 348 0 2.52
-14 650 14.1 0.61 147 37.6 345 0 2.52
-15 650 14.1 0.61 145 37.6 352 0 2.52
-16 650 13.9 0.63 144 38.1 364 0 2.5
-17 650 13.9 0.63 144 38.6 371 0 2.52
-18 600 13.9 0.63 142 38.6 379 0 2.52
-19 650 13.9 0.63 142 38.6 394 0 2.52

Note: Time represents engine run time before present


********************************
***** Freeze Frame Records *****
********************************


Fault Record: 1 or 1 @ 0 Hours
Fault Record: 81 or 51 @ 0 Hours

Total Engine Run Time: 112.1 Hours

Maximum Engine Speed: 155350 RPM Occurred @ 88.8 Hours

# of Rev Limiter Events : 2
Last Event Occurred @ 88.8 Hours
# of Engine Overheat Events : 2
Last Event Occurred @ 41 Hours
# of Low Oil Pressure Events: 0
Last Event Occurred @ 0 Hours
# of Knocking Control Events: 0
Last Event Occurred @ 0 Hours



***********************************
***** Data Parameter Snapshot *****
***********************************


Engine Speed : 0.00 RPM Engine speed
Intake Press : 30.1 inHg Intake pressure
Throttle Pos Main : 0.72 V Throttle position sensor(main)
Throttle Angle : 4.57 deg Throttle valve opening (0-90)
Throttle Pos Sub : 2.71 V Throttle position sensor(sub)
Throttle Req : 0.00 % Throttle request
LPS Port Main : 2.16 V LPS_PORT(main)
LPS Port Sub : 2.21 V LPS_PORT(sub)
LPS STBD Main : 0.00 V LPS_STBD(main)
LPS STBD Sub : 0.00 V LPS_STBD(sub)
Active Remote : 1P Active Remote Control
Shift Pos Main : 2.50 V Shift position sensor(main)
Shift Pos Sub : 2.53 V Shift position sensor(sub)
Shift Req : 0.00 % Shift request
Atm Press : 30.1 inHg Atmospheric pressure
VBattery : 12.1 V Battery voltage (12-16)
Fuel Inj Time : 0.00 ms Fuel injection duration
Ign Angle : --- Ignition timing
Engine Temp : 82.5 °F Engine temperature (below 302)
Intake Temp : 72.4 °F Intake temperature
Oil Press. : 1.11 psi Oil Pressure
Cam Timing STBD : 80.0 deg Intake cam timing (STBD)
Cam Timing PORT : 80.0 deg Intake cam timing (PORT)
Cool Pr. : 109 psi Coolant Pressure
Speed : 0.00 mph Speed
Stop SW : Off Engine stop lanyard switch
Shift Judgement : On Shift position judgment
Dual Eng SW : Off Dual engine system switch
Shift Cut : Off Shift cut-off
Overheat SW : Off Overheat thermoswitch
Main SW : On Main switch(wakeup)
Main SW : On Main switch(Receive data)
Start/Stop : Off Start stop switch
Startable : On Possible to start
Main RLY : On Main relay
Throttle RLY : On Electronic throttle relay
Fuel Pump RLY : Off Fuel pump relay
Shift RLY : On Shift relay
PT/T UP SW : Off PT/T up switch
PT/T DN SW : Off PT/T down switch


*******************************
***** Maintenance Records *****
*******************************


Oil Change Run Time Records: 0 records stored on ECM

Note: Current Engine Run Time = 112.1 Hours

Here is the rest of it:


*********************************
***** Active Fault Status *****
*********************************



13 Pulser coil Normal
# 15 Engine temp sensor Normal
# 17 Knock sensor Normal
# 19 Battery voltage Normal
# 23 Intake temp sensor Normal
# 24 Cam position sensor (EXH) Normal
# 27 Water in fuel Normal
# 29 Intake press sensor Normal
# 37 Intake air passage Normal
# 39 Oil press sensor Normal
# 44 Engine stop lanyard switch Off
# 68 Variable cam timing (STBD) Normal
# 69 Variable cam timing (PORT) Normal
# 71 Cam position sensor(STBD INT) Normal
# 72 Cam position sensor(PORT INT) Normal
# 73 Oil control valve (STBD) Normal
# 74 Oil control valve (PORT) Normal
# 86 Immobilizer Normal
#112 Elec. Throttle: ECM Error Normal
#113 Elec. Throttle: ECM Error Normal
#114 Elec. Throttle: ECM Error Normal
#115 Elec. Throttle: Throttle ValveNormal
#116 Elec. Throttle: Throttle ValveNormal
#117 Elec. Throttle: Drive Motor Normal
#118 Elec. Throttle: Drive Motor Normal
#119 Elec. Throttle: Mot Connector Normal
#121 Elec. Throttle: CommunicationsNormal
#122 Elec. Throttle: Drive Motor Normal
#123 Elec. Throttle: Drive Mot RLY Normal
#124 Throttle Position Sensor: MainNormal
#125 Throttle Position Sensor: MainNormal
#126 Throttle Pos. Character fail Normal
#127 Throttle Position Sensor: Sub Normal
#128 Throttle Position Sensor: Sub Normal
#129 Electronic throttle system Normal
#136 Elec. Throttle: CommunicationsNormal
#137 Elec. Throttle: CommunicationsNormal
#138 Elec. Throttle: ECM Error Normal
#139 Elec. Throttle: ECM Error Normal
#141 Elec. Throttle: TPS Voltage Normal
#142 Elec. Throttle: Return Spring Normal
#143 Elec. Throttle: CommunicationsNormal
#144 Elec. Throttle: Low voltage Normal
#145 Elec. Throttle: Throttle ValveNormal
#146 Shift position sensor Normal
#147 Shift position sensor Normal
#148 Shift position sensor Normal
#149 Shift position sensor Normal
#150 Shift position sensor Normal
#153 Shift position sensor Normal
#154 Shift position sensor Normal
#155 Shift position sensor Normal
#156 ENG-R.C. communication Normal
#157 ENG-R.C. communication Normal
#160 Remote control system Normal
#161 Remote control system Normal
#162 Remote control system Normal
#163 Remote control system Normal
#164 Remote control system Normal
#165 Remote control system Normal
#166 Remote control system Normal
#167 Remote control system Normal
#168 Remote control system Normal
#169 Remote control system Normal
#170 Remote control system Normal
#171 Remote control system Normal
#172 Remote control system Normal
#173 Remote control system Normal
#174 Remote control system Normal
#175 Remote control system Normal
#176 Remote control system Normal
#177 Remote control system Normal
#178 Remote control system Normal
#179 Remote control system Normal
#180 Remote control system Normal
#181 Remote control system Normal
#183 Remote control system Normal
#184 Remote control system Normal
#186 Remote control system Normal
#187 Remote control system Normal

Note: This list shows current faults only.
Please check the history section for stored
faults that are currently not active.


*********************************
***** Run Time History *****
*********************************

0-1000 RPM: 61.4 Hrs
1000-2000 RPM: 16.8 Hrs
2000-3000 RPM: 2.3 Hrs
3000-4000 RPM: 11.4 Hrs
4000-5000 RPM: 15.4 Hrs
5000-6000 RPM: 4.8 Hrs
6000-7000 RPM: 0.0 Hrs

Total Run Time: 112.1 Hrs

Looks like a lot of idle time

155,380 RPM is off the chart

I am not much help, just had to throw that in

Yes, it appears that the owner did alot of drift fishing.

and you wasted about 1/2 hour of your labor money on a STUPID compression test.
waste of time on a 4 stroke.



Boscoe.
F80TLRY.
cyl 1 140 PSI.
cyl 2 135 PSI.
cyl 3 138 PSI.
cyl 4 135 PSI.

motor GOOD? motor BAD????

motor went to 3 other techs before me.

Maybe so, but the leakdown test was done as you suggested.