Mercruiser Oil Pressure Problem

[Rblak]

I own a 1986 3.7L 170 hp Mercruiser I/O. When I first start it,
the oil pressure is 40 to 50 PSI at idle (1000 rpm). After
reaching normal operating temperature, at idle my guage reads no
more than 10 or so PSI. I can get it up to around 25 by jumping
idle to 1500. Cruising gets me around 40 PSI.

Can someone tell me what could be causing this? My auto keeps
its pressure constant at a variety of revs.

Thanks,

RBlak

74213...@compuserve.com

[Lawrence]

In article <5rop3v$qes$1...@mhafn.production.compuserve.com>, Rblak says...

How many hours on it? It's not that unusual for oil pressure to vary
based on rpm. The pump is driven by the cam so faster you turn faster
it pumps. There is a pressure relief valve so on a newer engine it
looks like the pressure never varies but the relief valve is keeping
it the same. I suspect the clearances on your lower end bearings are a
bit on the high side. Sounds like ok pressure while cruising.

[Jeff]

If you hear clicking noises, then worry.
If you engine seems to run just fine anyway, suspect
the pressure sending unit. the hole in these that the
oil pressure has to go through to actuate the transducer
is very small. maybe .010" or so. if it gets clogged, the
meter will read crazy. This happened in my wife's truck,
and an new sender, $12 fixed it right up.

--
Jeff Taipale <j.ta...@popmail.csuohio.edu>
http://ncweb.com/org/zionlc/vscapes/vscapes.html

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[Geoff Wakefield]

I had a similar question a couple of months ago. Unfortunately, I deleted
the response from Mercruiser. As I recall, it said a minimum of 4 psi at
idle and 30-55 psi at 2000 rpm. I have a different motor (4.3LX), but it
indicates a little over 40 psi once the oil is hot. I have seen other folks
respond that "around 40 psi" is what is indicated at cruise.

My guess is your engine is within specs. Your car probably never gets the
oil quite as hot as the boat does, and many automotive oil pressure guages
are not very accurate.

Rblak <74213...@CompuServe.COM> wrote in article
<5rop3v$qes$1...@mhafn.production.compuserve.com>...

>I own a 1986 3.7L 170 hp Mercruiser I/O. When I first start it,
>the oil pressure is 40 to 50 PSI at idle (1000 rpm). After
>reaching normal operating temperature, at idle my guage reads no
>more than 10 or so PSI. I can get it up to around 25 by jumping
>idle to 1500. Cruising gets me around 40 PSI.
>
>Can someone tell me what could be causing this? My auto keeps
>its pressure constant at a variety of revs.
>

>Thanks,
>
>RBlak
>
>74213...@compuserve.com