"Jim and Becky" wrote in message
...
Anyone know what psi reading I should expect on these 1988 200's?
On a new engine?
An engine that I probably don't want?

You should not be concentrating on absolute compression reading, The
compression reading will depend on humidity, air pressure, cranking speed
(battery charge) and a host of other factors. You should be concentrating
on the difference between the cylinders, a range within 5 psi is what you
ared looking for.

OK I agree, but if all six cylinders have 70-80 psi isn't there a problem?
I'm thinking the 120-140 psi range is what I'm looking for based of
something I read long ago.
Hence my latest question.


"Mark" Boatbasin@optonline(remove this).net wrote in message
...

"Jim and Becky" wrote in message
...
Anyone know what psi reading I should expect on these 1988 200's?
On a new engine?
An engine that I probably don't want?

You should not be concentrating on absolute compression reading, The
compression reading will depend on humidity, air pressure, cranking speed
(battery charge) and a host of other factors. You should be concentrating
on the difference between the cylinders, a range within 5 psi is what you
ared looking for.

"Jim and Becky" wrote in message
...

OK I agree, but if all six cylinders have 70-80 psi isn't there a
problem?

It could very well be. Was that the reading? Check your service manual.
The specs will be in there.

I'm thinking the 120-140 psi range is what I'm looking for based of
something I read long ago.
Hence my latest question.

Keep in mind, also, you are only allowed a certain percentage variation
between cylinders and that varies from make of engine and model etc..
Again, get a service manual. Or call the dealership. Get the correct
specs. If you don't know, you will be in trouble. A compression test
will detect the most basic defects and wear. On some engines, having a
high compression reading could mean having carbon build up, but that
mostly happens on lower RPM engines like Tecumseh or B&S engines. If
it's a EFI that should not be happening mind you. Still, get the specs,
look for variation and low compression. Anything that is out of spec,
run away from - unless you can get it dirt cheap.

It depends on the engine and what the manufacture lays out to you. 5
PSI may be acceptable for some engines and not others. It will be in
the "book". Or at least it should be.

I don't know the exact number for that particular year/engine. However, it
should be between 120 and 130.

If you get much below 120 I would be suspicious. Pick up a light scope
(small light on a flexible line) so you can see inside the cylinder. You
can see if there are any scratches in the cylinder walls around the intake
and exhaust ports.

Most problems occure on the intake port side due to water and/or poor
oiling.

Most problems occure on the exhaust side and or top of piston due to low
octane fuel/lean condition.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
wrote in message
oups.com...
"Jim and Becky" wrote in message
...

OK I agree, but if all six cylinders have 70-80 psi isn't there a
problem?

It could very well be. Was that the reading? Check your service manual.
The specs will be in there.

I'm thinking the 120-140 psi range is what I'm looking for based of
something I read long ago.
Hence my latest question.

Keep in mind, also, you are only allowed a certain percentage variation
between cylinders and that varies from make of engine and model etc..
Again, get a service manual. Or call the dealership. Get the correct
specs. If you don't know, you will be in trouble. A compression test
will detect the most basic defects and wear. On some engines, having a
high compression reading could mean having carbon build up, but that
mostly happens on lower RPM engines like Tecumseh or B&S engines. If
it's a EFI that should not be happening mind you. Still, get the specs,
look for variation and low compression. Anything that is out of spec,
run away from - unless you can get it dirt cheap.

On Tue, 1 Feb 2005 21:32:14 -0500, "Jim and Becky"
wrote:

I'm pondering (always will be) a boat with a pair of 1988 Yamaha 200's.
The seller says they have 1025 hours on them.

I have four of these on my 26' ranger. darn good engines.

Assume they weren't used commercially and have been well taken care of.
What is the life expectancy (total hours) of these?

These will run for 102k hours beforte a top end rebuild is needed.
look at a bottom end rebuild after about 600k hours.

Lets say we call them obsolete when they drop more than 15% of their
original output. I'm in an area I know nothing about but some power loss
might be expected due to worn pistons, etc.

One of thae bad things about these engines, it that the cams wear
down. this is where the power loss comes from. Simply replace the
cams, and you will be back at full power.

All I can think of is one motor dying about the first of July and getting
the boat back in the water around mid September.
I remember reading 10,000 hours for an inboard gas, maybe twice that for an
inboard diesel?

More like four times more. At least, that has been my experience.

"tony thomas" wrote in message
news:Oh5Nd.51517$eT5.37379@attbi_s51...
I don't know the exact number for that particular year/engine. However, it
should be between 120 and 130.

If you get much below 120 I would be suspicious. Pick up a light scope
(small light on a flexible line) so you can see inside the cylinder. You
can see if there are any scratches in the cylinder walls around the intake
and exhaust ports.

Most problems occure on the intake port side due to water and/or poor
oiling.

Most problems occure on the exhaust side and or top of piston due to low
octane fuel/lean condition.

Thanks, Tony. Yes, often (especially in a salt water used engine) you can
get a blockage from salt in the powerhead and that can cause over heating
and a virtual "frying" of the cylinder(s). It can happen even before the
powerhead in the copper water tube coming from the pump. I had a Merc. 90 HP
2-stroke with the water tube collapsed from salt at the base of the
powerhead and that restricted the water flow by about 50%, effectively
destroying that powerhead by over heating. I did rebuild it myself and I got
it going again for about $1500.00 in parts and machining for the complete
engine and gear case. Basically, it was a total rebuild of about 18 hours.
It runs just fine now. In fact, it's got a great deal of "snap" :-) And much
cheaper than a new unit. It's on the back of a 22' Boston Whaler now and 55
MPH is not a problem.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
wrote in message
oups.com...
"Jim and Becky" wrote in message
...

OK I agree, but if all six cylinders have 70-80 psi isn't there a
problem?

It could very well be. Was that the reading? Check your service manual.
The specs will be in there.

I'm thinking the 120-140 psi range is what I'm looking for based of
something I read long ago.
Hence my latest question.

Keep in mind, also, you are only allowed a certain percentage variation
between cylinders and that varies from make of engine and model etc..
Again, get a service manual. Or call the dealership. Get the correct
specs. If you don't know, you will be in trouble. A compression test
will detect the most basic defects and wear. On some engines, having a
high compression reading could mean having carbon build up, but that
mostly happens on lower RPM engines like Tecumseh or B&S engines. If
it's a EFI that should not be happening mind you. Still, get the specs,
look for variation and low compression. Anything that is out of spec,
run away from - unless you can get it dirt cheap.

My rebuild runs around 105psi and the non-rebuild
tops out around 95-98.

Again, This ABSOLUTELY does vary depending on
lots of factors than Im aware of such as,
hot/cold, throttle open or not, day of the week,
time of day, etc.

really.

I think this is why my book is so vauge on the subject. I
use it to look for trends and to compare cylinders more
than anything else.

70-80 does sound too low and 10psi is too large of a range
I think. Your lower cylinders will read a bit lower.

db


"Jim and Becky" wrote in message
...
OK I agree, but if all six cylinders have 70-80 psi isn't there a problem?
I'm thinking the 120-140 psi range is what I'm looking for based of
something I read long ago.
Hence my latest question.


"Mark" Boatbasin@optonline(remove this).net wrote in message
...

"Jim and Becky" wrote in message
...
Anyone know what psi reading I should expect on these 1988 200's?
On a new engine?
An engine that I probably don't want?

You should not be concentrating on absolute compression reading, The
compression reading will depend on humidity, air pressure, cranking
speed
(battery charge) and a host of other factors. You should be
concentrating
on the difference between the cylinders, a range within 5 psi is what
you
ared looking for.