Lower than I like Oil Pressure
08-14-2014, 10:18 AM
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Lower than I like Oil Pressure
Two new 540s. On all the dyno runs op was high 60s low 70s. Once installed in the boat on start up it'll be mid 60's but on a moderate run it'll drop to mid 40s and after the run it'll drop to mid 20s at idle. Standard merc coolers, no oil temp gauge but I shot the filters with a digital infrared and temps were right around 200 after a full throttle run of about a two minutes. I'm running Joe Gibbs 15w50 full synthetic. Ive used both wix and K&N filters with exact same results. Any ideas why I'm dropping oil pressure like this? On all dyno runs it never dropped below 70 on a 5500 rpm pull. I realize I've added a cooler and lines where I didn't have those on the dyno but it's high 60s on cold start up.
08-14-2014, 10:29 AM
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What was your oil psi at WOT at or near end of the two minute run ? And what was that WOT rpm ?
08-14-2014, 10:45 AM
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I'm comfortable with that with stock 4.3's/5.0's/5.7's/330hp 454's / with crappy stock gauges and crappy dash electrical systems....I don't get concerned.
high performance motors, you bet. Hopefully it's just a guage/sender/ low voltage to guage issue. If all is okay there (double checking with mechanical gauge) I'd try another oil with higher base number. Like a 20w/50 or a straight 40 Maybe.
That OP may be fine if it is what it really is, but I've never been in that territory so if it was mine I'd be digging into it.
The 20's at idle (only) don't worry me too much.
high performance motors, you bet. Hopefully it's just a guage/sender/ low voltage to guage issue. If all is okay there (double checking with mechanical gauge) I'd try another oil with higher base number. Like a 20w/50 or a straight 40 Maybe.
That OP may be fine if it is what it really is, but I've never been in that territory so if it was mine I'd be digging into it.
The 20's at idle (only) don't worry me too much.
08-14-2014, 11:40 AM
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Pumps are Melling 10774, standard volume, high pressure pump. Just talked to Melling and they said running through lines and a cooler what I'm seeing is normal. I wish I'd used a high volume, high pressure pump now but I was worried about pumping the pan dry on extended runs.
08-14-2014, 01:21 PM
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If you are using the stock merc oil lines, cooler, block adapter on a 540 you have removed the pin from the grenade...unless they are from the higher HP motors they are junk, need good block adapter w/1/2" fittings, larger oil cooler with same size lines as well as the filter adapter and use #10 lines...then go from there..
08-14-2014, 01:24 PM
#9
Are you using the stock Merc lines and fittings going to the cooler? That may be part of your problem, as the ID of those lines is actually pretty small, and they can be restrictive. Ditto for the stock remote oil filter adapter. See Arcticfriends' thread about oil systems that is a sticky on this forum. I'm running the stock sized cooler too, but I switched to a thermostatic sandwich oil filter adapter and went with #10 stainless lines and fittings to the cooler. This eliminated several feet of line and cut down on restrictions to flow.
