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Mercruiser Mark iv oil temperature issue

Old 06-15-2022, 11:44 AM
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Default Mercruiser Mark iv oil temperature issue

Hey guys, Sorry for the long post but I need some advice. I have a pair of 370 454s, basically 454 mags. Just installed new cams, distributors and intakes. Comp xtreme marine cams 234/244, weiand single plane intakes and D.U.I. distributors. The motors have 990 heads. First run at the lake idled fine cold with 70 psi oil pressure on port motor and around 60 psi starboard. After only about 1 mile of running, not even hard running, 3500-4000k rpm my port oil temp held around 170 but starboard had already shot up to 250. Buzzer went off so I shut down and idled back. I then installed larger oil coolers from mr cool. Roughly 2x17 tandem on starboard and 2x12 single on port. I also installed new bypass valves in the block mounted remote filter pad. I used factory part numbers for these. Took it out today, same scenario. Same psi at idle but after only about 1-1/2 miles at semi hard running starboard motor shot up to 250-270 while port held 170. Oil pressure also dropped low on hot motor. I brought it down to idle and pressure slowly increased as temp decreased. Im at a loss, both are plumbed the same. Larger oil cooler made 0 difference. I would have at least expected some change. Water is pumping good. Water temps never got above 160. Any help here is appreciated.
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Old 06-15-2022, 11:57 AM
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I did notice a slight difference last year in oil temps and pressure before the changes but it seems like the new parts have really amplified it.
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Old 06-15-2022, 12:00 PM
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What are the water temps doing in these motors?
Are you sure ignition timing is correct in both?
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Old 06-15-2022, 12:09 PM
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Originally Posted by DrFeelgood View Post
What are the water temps doing in these motors?
Are you sure ignition timing is correct in both?
read the second to the last sentence
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Old 06-15-2022, 12:14 PM
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Typically water flow issue, tune issue, or motor coming apart (bearings) issue. Id pull the oil filter first and cut open looking for bearing material. If that looks good, hopefully right , double check timing then pull carb apart and give it a good twice over snd cleaning. You went thru all the water flow isdues right ? Even thru drive thru transom ?
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Old 06-15-2022, 12:15 PM
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Originally Posted by F-2 Speedy View Post
read the second to the last sentence
Missed that. Thanks.
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Old 06-15-2022, 12:40 PM
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doesn't sound like the oil is getting to or through the cooler, did you upgrade the oil lines ?
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Old 06-15-2022, 01:46 PM
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I kept the original oil lines. Water passages are all clear the best I can tell. I have transom pick ups, Sea strainers and Sea pumps. Impellers are both new and water pressure is around 12 psi on both engines when running. I have dry to the tip exhaust and both engines seem to be pumping water out fairly equally. Ignition timing is set up at 12 initial with 24 advance all in at 3000. I need to double check the total advance. I double checked the initial at 12 but have not double checked my total after it was on the lake. I had it set at 36 at 3200 RPM.
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Old 06-15-2022, 01:48 PM
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I have velvet drive transmissions so my transmission coolers are the very first stop after the water pumps. I did check those to make sure there was no water obstruction there. Everything looked clear and clean. Oil coolers are both brand new. I almost suspect that the majority of the oil is not making it to the cooler. What could cause this???
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Old 06-15-2022, 02:03 PM
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how are the oil lines plumbed to the cooler, with the water flow or against
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