Information about information and oil pressure issues

This is a sticky topic.
  • Filter
  • Time
  • Show
Clear All
new posts
  • Don Moyer
    • Oct 2004
    • 2823

    Information about information and oil pressure issues

    INFORMATION about INFORMATION: Thanks to the Community Forum, we can now find solutions to most any issue we may have in maintaining and servicing the Atomic 4, and using the Forum as a platform, build on the information and share the result back with everyone else involved in that particular conversation. Typically, 500-700 people visit the forum each day. Here’s a link to the home page of the forum, if you’ve never checked it out (it deserves to be in your “Favorite Places”):

    It’s increasingly difficult for me to stay out in front of most of the conversations on the Forum, the best example being the body of information now available in the “Electrical” section for any of you who want to integrate the very latest technology into your boat’s house DC circuit. This very morning, I referred an email customer to that section of the Forum with the following links:

    My first tip in this technical note is to encourage you to develop the ability to navigate within the Community Forum (it’s my understanding that it now has a more powerful search capability than even a month ago).

    The second most active method of rendering technical information continues to be our email outreach at This method enables us to engage in one-on-one conversations in a very efficient manner (as compared to being tied to a telephone and playing phone tag), and it provides a convenient paper trail for follow-up. Please note, however, that only accesses my personal insight; the Forum gets you a community solution.

    There is, of course, our Technical Service line (410-810-8920). This avenue still has value for detailed rebuilding problems that really do benefit from “real time” conversation, or for those few of you who do not have computer access (nor any friends with computer access).

    Lastly, technical notes to email subscribers will continue to be used as a viable method of sending out important announcements that have fleet-wide implications, e.g., workshop dates, and important technical information which we have not seen discussed anywhere else. In general, however, we make the assumption that if you have Internet access (which you must have, if you registered for our email list), you are already in touch with the other, more timely, methods of obtaining technical service, so the frequency of email technical notes via this medium will likely drop to several a year as opposed to every other month or so, as in the past.

    OIL PRESSURE: Speaking of a subject with potential fleet-wide implication, oil pressure is one subject for which there has never been a plethora of information created – even on the Internet. There is, however, an important thread beginning in the Troubleshooting section of the Forum relative to loss of oil pressure.

    The scenario in this particular posting is that oil pressure starts out being within the normal range (normal pressure described at the end of this section). It then drops dangerously low over a period of several hours of operation at normal cruising power settings, which we assume happens when the oil thins after the temperature of the cast iron oil pan finally catches up to the temperature of the rest of the engine. This particular situation has apparently deteriorated to the point that the pressure regulating valve has been adjusted in to the stop and pressure continues to drop after several hours at normal cruising power.

    Except for a somewhat generic list of possible causes of low oil pressure in their troubleshooting guides, we have not been able to find any mention by Universal which speaks to the specific issue of oil pressure starting out normal and then decaying after several hours of operation at cruising power. Their generic causes of low oil pressure are using oil with a body that is too light, a worn oil pump, worn bearings, and a broken regulating valve spring. While many are prone to believe that worn bearings are the main cause of low oil pressure, our own experience does not confirm this conclusion. We have disassembled many engines in search of a reason for low oil pressure only to find the main, rod, and cam bearings in perfect condition. Conversely, we have disassembled many engines with completely failed main or rod bearings with no previous reports of oil pressure problems.

    Regarding worn oil pumps, we have grown suspicious that pump performance might be at the heart of these cases of decaying oil pressure over time. However, since the gears of the oil pump are integrated into the rear main bearing cap and the flow of oil is fed directly into the internal oil galley, there has historically really been no ability to test the performance of the pump independently – even during overhaul. For this reason, our shop technicians recently built a separate test stand on which to mount the rear main bearing cap (with the oil pump gears installed). This test stand gives us the ability to test oil pump output at specific RPM, pressure, and flow rates. From these tests, we were easily able to devise a pass-fail threshold at which pumps can be safely reused or rebuilt; but unfortunately, this breakthrough is only useful if you’re holding the oil pump in your hand.

    I come to this point in the discussion of oil pressure somewhat apologetically, since I can’t bring it around in the usual fashion of recommending steps 1 though 4 to solve the problem. What we can say is that, given the alternatives, we suggest trying the following long shots before removing the engine to remove and test the pump (listed in increasing order of cost):

    1) Try an oil with heavier body. We don’t recommend heavier than a 40 or 10/40 weight oil. Beyond this weight, the hydraulic oil cushion between the crankshaft and main and rod bearings will become inconsistent, even though you might see a more comforting indication on your oil pressure gauge.

    2) If not already installed, we recommend trying a new early model style regulating valve (OOIL_06_122 in our online catalog; search the catalog using the keyword "122", without the quotes). We have never seen a broken regulating valve spring, but we have seen late model style spring and ball regulating valves that simply lost their ability to control oil pressure in high time engines.

    3) If you find yourself gaining on the problem at all, we recommend re-facing the seat in the regulating valve. The inexpensive way is to slip a 1/8” pipe nipple (approximately 4” long) over the sliding part of the early model regulating valve and gently tap the nipple as you rotate the valve to provide a better seat between the valve and the seat. The more expensive way is to buy one of our reseating tools which has the ability of “machining” a small bevel in the orifice of the seat (TOOL_05_172 in our online catalog).

    4) If all else fails and you end up removing the engine, it is not usually necessary to completely rebuild the engine unless other factors indicate the need to do so - e.g., low compression, plugs fouling quickly, excessive blowby, etc.

    As somewhat of an afterthought, “Normal” oil pressure itself has been somewhat of a moving target within Universal’s technical data over the years. Relying on the handful of owner’s manuals from the 1970's, one of them calls for a factory setting of 50 to 55 PSI cold, with idle as low as 5 PSI. In another manual, cold factory settings are listed as 40 to 50 PSI with an idle pressure of 10 PSI, and elsewhere in the same manual cold pressure is listed as 35 to 45 PSI. Universal’s recommendations for an engine fully warmed up are: 40 to 45 PSI at 3000 RPM, 30 to 35 PSI at 2500 RPM, and 10 to 25 PSI from 1000 RPM to idle.

    In aviation circles, we used to talk of “action thresholds”, which were cockpit indications that required serious actions, sometimes along the lines of ejecting from the airplane in case of dated single engine fighters. In the recreational sail boat fraternity, an “action threshold” for oil pressure might be the pressure below which you would not want to operate the engine continuously at cruise without expecting to encounter some level of engine damage. A rule of thumb for such a threshold is 10 PSI for each 1000 RPM. This rule of thumb works out to be just a bit below Universal’s lower figures in each of their ranges - e.g. 25 PSI would be the action pressure for 2500 RPM, etc.

    On a completely different track, each year at this time we start getting calls for assistance from folks who have over cranked their engines on the starter and flooded their exhaust systems, causing water to flow back into the combustion chambers. I therefore can’t bring myself to end this technical note without reminding those of you who are relatively new to our fraternity to please remember to close your raw water through hull valve if you end up cranking your starter longer than usual in starting your engine after a winter lay-up (or any other time for that matter) to avoid this devastating scenario.

    Warmest regards, and our best wishes for a wonderful 2009 season,

    Don and Brenda Moyer and the entire MMI team
    Last edited by Administrator; 04-16-2009, 07:48 AM. Reason: Repair broken link.