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Pete Jung

Mar 29, 2020, 12:31:15 PM3/29/20
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My  1978 Tolly 48 has two CAT 3208 N/A engines installed.  Each engine has two oil filters, mounted upside down on a common mounting base.  Am I correct in assuming, once the engine has shut down, that the oil contained in each filter drains back into the sump?  If not, how in the heck do you remove the filter(s) without dumping a quart or so of dirty oil all over the engine?  And I am familiar with the trick of poking a hole in the top of the filter can, to ensure there is no vacuum holding oil into the filter, prior to unscrewing it.  But just not sure how else to ensure the filters' are empty prior to removal.  

And the obvious related question-I presume if the filters are NOT full at startup, as the oil has drained back into the crankcase, that I don't have to pre-fill the new filters prior to installation.  

Note that my engine manual seems to be somewhat generic (not marine specific, for instance) in that it shows only a single filter, mounted upright on a side-hung bracket.  Not at all like my installation.


Mar 30, 2020, 2:11:19 PM3/30/20
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I don't know about your specific set up, my '79 40 with 3208s has the standard single filter.   Sometimes the use of dual filters is to have one full flow and one bypass filter rather than the standard single full flow unit. Other times it's just a pair of full flow filters.  I've seen dual filters in stationary equipment (generators, pumps, etc).  

 In any case the oil filters should not drain on shutdown, especially the full flow one. Typically there's a check valve so that you develop oil pressure as soon as the engine starts.   Punching a hole in the top is probably the best you can do, I've had other equipment where you had to do that for this exact reason, be sure to allow 30 min or so for it to drain.  I've never been able to get this type of setup off completely cleanly so assume some oil will spill anyway, so lots of oil absorbs and a drip pan if feasible.  

Pete Jung

Apr 7, 2020, 8:58:39 PM4/7/20
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Thought I'd post an update on this issue, just for grins. After much research, I determined that the CAT filters (1R-0734) on my 3208 CATs do NOT have anti-drain-back valves. Neither do the filter bases upon which they're mounted. Thus, the filters empty soon after shutdown. When I removed my upside-down filters for an oil change, very little oil remained in the filter housings, so cleanup was easy. And access is certainly improved in my Tolly 48 with the filters upside down.

A previous owner inverted the filter bases sometime in the past, although I'm not sure why. Clearance under the filters appears adequate, so with some effort, the bases and filters could be turned right-side up again (filter screw threads up). But I see little need to change the arrangement. Oil pressure builds within 2 seconds of startup, and the filters apparently do not need to fill before oil pressure is satisfactory, or they fill in a heartbeat.


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