compression test on LF200XCA yamaha 200. is this right?

[gp03271965]

Thinking about buys a 2016 boat with twin yamahas. They did compression and all the cylinders and coth engines are right around 260? Is this right?

[99yam40]

who is they and what is coth

[gp03271965]

Marina.. what is coth?

[99yam40]

Do you trust what the marina tells you?

I know 4 strokes have higher compression that 2 strokes, but I do not know if 260 is correct

You are the one that wrote coth 1st.

[boscoe99]

Where is our resident boar hog man?

[walleye1]

Teat on a boar hog man.

[rodbolt17]

here I am to save the day
folks a compression test can be very misleading.
it WILL NOT find minor valve leakage nor gasket leakage.
couple that with a leakdown is faster and more accurate why bother with compression.
get OUT of the old two stroke smoke mode.
let me tell ya a story about a man named jed.
jed called me up last momday,motor idles,accerates and runs top end.
just blew about 1.5 qts of oil into the bilge.
he ran his own compression test.
140 or so on 5 cylinders 80 on #1.first 5 look pretty good,ehh.
motor is a BARR marine 4.3 longblock placed into service last may.
possibly more on this stupid warrenty saga with Barr later.
he brought it in Thursday took me about 30 min to leakdown test all 6.
#1 80% mostly rings some intake.#2 45% rings,#3 65% mostly rings some intake,#4 40% all rings.#5 30% rings,
#6 50% rings and some intake.
so now he wasted time on a compression test that did not catch the fact that ALL 6 are hosed.
the distributer has no service dept nor techs.
Barr says send them the cyl head and they will send it to Baar and Barr will send it to the parent company Indmar.
I figure 3 weeks after I send the head out I will be making phone calls tring to find out which coconut shell my head is under.
and why bother sending a head when it is a block issue ???????????
I have 5 weeks to have this boat back in service for peeler season.
most likely it will have a Volvo longblock like I tried to sell him last spring.
had it been a Volvo block assy a new one would have been on its way Friday.
part of the problem with buying on the net, try to get 5000 dollars worth of stuff warrentied.

[panasonic]

Thanks Rodnut, that was a good story and I enjoyed reading it.
I agree the leak down test is the much better test of an engines health.

But I also believe a compression test still a quick and dirty way to get an idea what may be going on in an engine.

[rodbolt17]

while you are still setting up for a compression test I am done with a leakdown test.
remember the TRURE story of the F115????
all 4 cyl were within 5 PSI,2 other local mochanics actually wrote the results with a sharpie on the cam cover.
while you are still fumbling with either a remote starter or walking from the back of the engine to the key switch.
procedure for a leakdown test for an F115.remove sparkplug cover, same as compression testing.
remove plugs,still the same.
now is where it changes.
spin the flywheel to the #1 TDC mark with the leakdown ADPTER installed in #1.
when you hear air hissing you know your coming up on #1 TDC compression stroke.
line up the marks, hit the tester.
rotate 180 hit #3,rotate 180 hit #4,rotate 180 hit #2 never stepped off the ladder and I am done bun.
if all is good in da hood install plugs and cover.
if not all good in da hood now I know WHERE the seal failure is.
intake valve,Ex valve,rings or a head gasket.
the F115 115 with (acceptable) compression actually had a head that corroded from a water passage to the cyl.
my first clue was removing the plugs and carefully inspecting them and noticing the tiny green flecks on the ground electrode.
the LEAK down rate on #3 was about 80%.