New Yamaha F150XB compression test

[panasonic]

compression test = teat on a boar hog.
a leakdown is way faster and way more indicative of a problem.
read very carefully the Yamaha test numbers, you will find there are no definitive numbers. there are definite limits on leakage numbers.


it is kinda like the maint schedule. appears NO BODY understands the word OR.

I agree with you on that mister...

[pstephens46]

5 years ago my F150's teats checked out at 170, 170, 175 and 165. 2005 model.

Wonder what readings Fairdeal would get with 1800 hours?

[rodbolt17]

I checked an F115 some years back at 140,135,138 and 140.
motor was bad.
leakdown was 90% on the 135.
culprit was a corroded head allowing water intrusion.
two other techs missed it.
symptom was poor idle.
lady had already spent almost 600 dollars on various other "fix's" .

someone even wrote the compression test numbers on the cam cover so proud they were.

removed the head,sent it down to flagship marine.
installed the repaired head and off they went.

compression test = teat on a boar hog.
I can do a leakdown in 10 min and never get off the ladder.
flywheel is already indexed and the fireing order is 1,3.4.2.
boom, done.
test 1,rotate 180*test 3 rotate 180*test 4 rotate 180* test 2, put the tools up.

[boscoe99]

What happens if a cylinder wall is scored below the point where the piston rings reside at top dead center? Motor runs like crap.

Will a leak down test indicate that?

[rodbolt17]

yesb ut the spark plug will tell me.
turn down the inlet air pressure and move the piston down and lock the flywheel and test it.
it is very simple and a compression test will miss a low wall score.
and I don't have to hook up remote starters or constantly climb off the ladder and to the helm and back to the ladder.

[panasonic]

If that motor does not have 175 plus psi I would be very disappointed.

please explain briefly how you get 175psi with a 9:1 engine while just cranking over....me not understand that...thanks

[TownsendsFJR1300]

compression test = teat on a boar hog.
a leakdown is way faster and way more indicative of a problem.
read very carefully the Yamaha test numbers, you will find there are no definitive numbers. there are definite limits on leakage numbers.

it is kinda like the maint schedule. appears NO BODY understands the word OR.

If you read the OP's first post, he DOESN'T HAVE ANY ISSUES.

There's NO reason to do a leak down test, period...*(compression test just as he's curious
the actual #)*

He simply wanted to know what the actual compression is, in a new motor.


appears NO BODY understands the word OR



.

[boscoe99]

Can someone/anyone give me a reference to any Yamaha service manual where a leakdown test is specified, together with pass/fail standards?

[TownsendsFJR1300]

Can someone/anyone give me a reference to any Yamaha service manual where a leakdown test is specified, together with pass/fail standards?

No, but your leak down tester gauge will have a chart (see below)

Example, Rings leaking on a mower engine say 15%, and say any yamaha OB, 15%, is NOT good.

I've used the leak down tester on many engines and found the rings leaking BADLY with the tester (on a weed eater-2 stroke) alone.
Pulled the cylinder and head, rings were carboned up REALLY BAD But had a fair amount of compression.. (my neighbor gave me the unit when he moved, said he checked them and they were fine). Engine wouldn't run over 2500. Cleaned up, 7,000 RPMs. Ran great and since sold it..

[fairdeal]

Can someone/anyone give me a reference to any Yamaha service manual where a leakdown test is specified, together with pass/fail standards?

Perhaps something taught in Kennesaw

(along with "since 03 mercs are not anywhere connected with Yamaha or Yamaha connected to mercs."

[pstephens46]

The master tech here in Savannah prefers leakdown tests also. Maybe it is a Kennesaw/Atlanta thing...

[TownsendsFJR1300]

The master tech here in Savannah prefers leakdown tests also. Maybe it is a Kennesaw/Atlanta thing...

The leak down test IS the best way to find an issue. No doubt..
If you've done any troubleshooting "hard parts" on an engine, (not electrical), it's a no brainer...

If you've never used one, it's a great investment and pays itself
off really quickly narrowing down where to look. You will need an air compressor.

And you better lock the crank up tight as it WILL TRY to spin the engine over...

When I test, I use the max, 100PSI... Makes finding and issues that much faster.


.

[Seanic08]

Okay, finally got through the 10 hours break-in period today. I will do a compression test (hopefully soon) and report back my numbers.

Thanks for the tip on killswitch...wonder why I never thought of that before.

[panasonic]

please explain briefly how you get 175psi with a 9:1 engine while just cranking over....me not understand that...thanks

bump to top....

[panasonic]

If that motor does not have 175 plus psi I would be very disappointed.

After a little relearning I have my mind wrapped around this again.......

I found a fairly simple explanation and some really detailed ones as well..

Dynamic Compression Ratio.

Dynamic Compression Ratio explained by Kennedy's Dynotune