Mercruiser Mark iv oil temperature issue
#31
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Definitely do it twice. I thought I had everything ready to rock before I put a load on the motors but it didn’t work out for me. Waste of time and money. To be fair, I was warned not to do it. I thought, they’ve lived all these years on flat tappet cams, why not? Well, I learned a hard lesson. I’ve had good luck in small blocks but never again in big blocks. I wish you the best of luck. I truly hope yours work out better than mine.
#32
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Check your oil lines I believe there is an arrow on top of the remote head. Or remove filter from head use remote starter switch click it for a couple seconds and see what hole oil comes out of.. I learned this the hard ways. Lines were reversed and would not send oil thru the filter so no cooling. If you have metal shavings it takes a lot of work to get them out of everywhere. I paid machine shop and they tanked them twice. Did you put a temp gun on oil filter?
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I didn’t use a temp gun, just going off the gauge. My sensor is mounted on an outlet port of the remote mount on the block. Tore into it a little further tonight before I remove it from the boat. Lifters are smooth but the cam lobes look rounded off on 1 intake and 5 exhaust. I’d bet when I pull the cam there will be others as well.
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Unfortunately, I’m better new bearings are going to be needed as well. I think I have settled on Lunati retro rollers for the next round. 226/236 114 LSA. It’s the closest I can find to a crane 731.
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#36
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#5 in inlet
Block to cooler first would not protect it from debris
Last edited by 35fountain; 06-21-2022 at 06:32 AM.
#37
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I checked mine after your statement. I have a gen 4. Mine go from block to filter then to cooler near water inlet. as per Mercruiser's diagram on mercruiserparts.com. That always bothered me because the way a heat exchanger works is opposite flow. Water in oil out. Oil out water in. But would it really make a difference with such a small cooler. I deal with a lot of water cooled heat exchangers. in my business.
As far as oil cooler, if i remember correctly, some say 10-15* oil temp cooler if oil tuns reverse direction of water. Been a long time since those discussions, i guess we should do a search.
Speaking of filters, when they are hanging down, I use Napa 1061/Wix51061 and 1069/ 51069 (a little shorter than 1061’s) as they don’t have relief valves.
Last edited by SB; 06-21-2022 at 07:13 AM.
#38
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I agree. It does make sense to filter the hot oil and then send it to the cooler. Mine go through the cooler first then filter before returning to the block. They were rigged that way when I bought it. I think I’ll reroute my lines to your diagram when I reassemble them.
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I remember this thread awhile back. I may switch my oil flow direction at my cooler