Here's my experience with vacuum gages. I have a Lehman 135. The primary
filter is a Racor 900 with 2 micron filters. The final is now a Racor
Spin-on with a 2 micron cartridge. I always check the vacuum gage on the
Racor underway, and it NEVER shows any vacuum. I even let that filter go too
long and pulled it out looking like it was coated with black jelly... still
no vacuum or effect on the engine. The filter is just HUGE compared to what
the Lehman sips... about 4 gallons/hr. consumed, 1.5 GPH or so returned. I
even took the vacuum gage off awhile back to make sure it was working; it
was fine.

If you have a filter that's really big compared to what your engine uses,
you'll almost never show any vacuum.

--


Keith
__
It's only unethical if you get caught.
"Doug Dotson" wrote in message
...
I'm installing a gauge as well, readable from the steering station. When
I owned the Yanmar, I chose to abide by what the manufacturer said
rather than risk my warranty. I'm funny like that. New system is going to
take into account all the good advise you and other have offered. I'm
not going to get caught with a dead engine again.

DOug

ps. Get a bigger dog

"RichH" wrote in message
...
If a 0.000000000002 micrometer rated filter has enough surface area it
will operate with LESS differential pressure than a small surface area
filter with 3 METERS pore size.

This is a vacuum pump ... meaning that it only has to deliver 15 psi
motive pressure plus about 2-3 feet of static head. A small dog can ****
harder than that.
The service advisory simply admits that Yanmar has a WEAK pump!!!!!!! A
pump that cant run against a 'dead-head'is cheap, ill designed, etc.

A clogged filter will always place stress on the pump. A filter begins
to become 'clogged' when approx 85% of its 'dirt capacity' is used, less
than that the pressure drop is linear, after that it rapidly accelerates
the rate of 'clogging' (becomes exponential) ..... thats why you NEED a
gauge to monitor it.