OB Compression test
 

Safe to crank it - don't start it. You don't have a set of muffs?

-W

"Scott W." wrote in message
...
Is it safe to crank over an outboard to test compression without
putting the lower unit in water, or will you damage the impeller?

Scott W.

"Scott W." wrote in message
...
Is it safe to crank over an outboard to test compression without
putting the lower unit in water, or will you damage the impeller?

Cranking it, yes, you are safe, just don't start.
On a pull-start, should be at least 3 full hard
pulls, on electric start, a few seconds. Like the
other poster posted, if you got ear muffs, put
em on if you are concerned. If its a running
motor, then just test compression after you
take it out of the water so there is still some
wetness in the column. But you'll be ok. More
interestingly is the question of what yer doing,
and why your are doing this? - what motor,
and why are you doing compression test - you
suspecting something, or just spot checking, or
buying a second hand motor or someting ? If
under 150 Psi, I might be concerned, and if
*any* difference at all between cylinders on
a multi-cylinder maching I'd be very concerned.





Scott W.

IIRC, you do a compression test by replacing the spark plug with the
compression meter. You normally pull all the plugs if there are more
than one cylinder. So how can it start? (I've never done this on a
two stroke, just on auto engines. Is something different?)

"Clams Canino" writes:

Safe to crank it - don't start it. You don't have a set of muffs?

-W

"Scott W." wrote in message
...
Is it safe to crank over an outboard to test compression without
putting the lower unit in water, or will you damage the impeller?

Scott W.



--

On Wed, 03 Nov 2004 22:38:05 -0800, Scott W. wrote:

On Wed, 03 Nov 2004 13:31:17 GMT, Short Wave Sportfishing
wrote:

Why do you feel the need to test compression?

Want to check out a motor before buying. I don't know what situation
it's in, a garage, basement, whatever, 'til I go to see it. Its
getting real cold up here (Ontario Canada) and I doubt its on a boat
at this time of year.

Then just crank it over - no need to get overly complicated.

However, compression tests don't tell the whole story - it would be
nice it you could start and run it for five minutes or so.

Later,

Tom

"Short Wave Sportfishing" wrote in message
...
On Wed, 03 Nov 2004 22:38:05 -0800, Scott W. wrote:

On Wed, 03 Nov 2004 13:31:17 GMT, Short Wave Sportfishing
wrote:

Why do you feel the need to test compression?

Want to check out a motor before buying. I don't know what situation
it's in, a garage, basement, whatever, 'til I go to see it. Its
getting real cold up here (Ontario Canada) and I doubt its on a boat
at this time of year.

Then just crank it over - no need to get overly complicated.

However, compression tests don't tell the whole story - it would be
nice it you could start and run it for five minutes or so.

A squirt of oil and a worn engine will show good in a compression test. Run
an engine untill warm, can it idle at lower than normal rpm smoothly? look
at the exhaust what color is it (oil or water vapor in the exhaust) then
remove the distributor coil wire and test the compression. Look at the
engine oil. Also many times a salt water engine will overheat at full load
because of rust and scale in the cooling system. How do you check for that?

On Thu, 04 Nov 2004 06:49:31 -0500, Harry Krause
wrote:

Short Wave Sportfishing wrote:
On Wed, 03 Nov 2004 22:38:05 -0800, Scott W. wrote:

On Wed, 03 Nov 2004 13:31:17 GMT, Short Wave Sportfishing
wrote:

Why do you feel the need to test compression?

Want to check out a motor before buying. I don't know what situation
it's in, a garage, basement, whatever, 'til I go to see it. Its
getting real cold up here (Ontario Canada) and I doubt its on a boat
at this time of year.

Then just crank it over - no need to get overly complicated.

However, compression tests don't tell the whole story - it would be
nice it you could start and run it for five minutes or so.

Back when I was single, I used to give some of my dates those same tests.

Sadly, I am somewhat deprived in that area - I married my high school
sweetheart.

Later,

Tom

"Beware the one legged man in a butt
kicking contest - he is there for a
reason."

Wun Hung Lo - date unknown

On Thu, 04 Nov 2004 11:36:31 -0500, Harry Krause
wrote:

Short Wave Sportfishing wrote:

Want to check out a motor before buying. I don't know what situation
it's in, a garage, basement, whatever, 'til I go to see it. Its
getting real cold up here (Ontario Canada) and I doubt its on a boat
at this time of year.

Then just crank it over - no need to get overly complicated.

However, compression tests don't tell the whole story - it would be
nice it you could start and run it for five minutes or so.

Back when I was single, I used to give some of my dates those same tests.

Sadly, I am somewhat deprived in that area - I married my high school
sweetheart.

I was going to, but she married someone else when I went off to
"collidge." Just as well, though. I wonder whatever happened to
her...Hillary Rodham was her name.

MUST - NOT - COMMENT - MUST - RESIST..... :)

Later,

Tom