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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    So just looked at my old thermostat that I had laying around. Looks like its a 140 and I replaced it with a 160. So it could just be that my old thermostat was a 140 and 160 was my normal operating temp. So going to go back to a 140 tomorrow and replace the ball/springs/rod.
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    Since my risers never get hot at all (in fact they are usually cool to the touch), maybe Im just getting air in the system and the Tstat housing is just really hot? The surface temps in Lake Michigan rarely get over 75f.
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    Is the water pocket cover in the drive? If yes, the entire drive is only 2 years old.
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    My next step is to replace the rod/balls/springs and sand down the opening they are in on the tstat housing.
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    When I said I replaced the water pump in the prior post, I meant that I replaced the entire water (circulation) pump on the front of the engine. The raw water impeller and housing in the drive was the first thing I replaced when I started the investigation. The impeller was the original from...
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    So just finished replacing the power steering cooler - man that was a pain. No blockage at all in there and it was the straight through design anyways. You would have to have something the size of a golfball to block it. Then replaced the water pump. Still got up to 175 to 180 at idle in the...
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    Looks like you have to cobble together/hack random hoses and the sensor to get 87290A23 to fit. So I'll see if the other items and backflushing clear the issue up before I get a new thermostat housing. Hate that they just stop making parts.
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    I also just ordered a new PS cooler from Mr Cool and water recirculation pump - they are the only original accessories left on the motor so I thought I might as well. If I want to replace the thermostat housing, is 87290a23 really the right way to go, or do some type of conversion?
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    Impeller and complete housing was replaced. Old impeller that came out was still perfect.
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    Judging by the diagram, I almost want to say the power steering cooler is probably junked up. Whats the official flow rate that is supposed to be making it to the housing from the inlet for a 5.7? Thanks for the picture edit and the diagram. You guys are the best!
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    1989 Mercruiser 5.7 slight overheating at lower RPMs

    Raw water cooled. Fresh water only. Alpha 1 Gen 1 drive. Drive is a newer OEM merc with 2 years on it. Motor is 1989 5.7 - unsure on serial number. Use the boat for trolling on Lake Michigan. Was out in fairly rough water last Sunday and trolled on the main. Looked down and the temp...
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    Need some recommendations for gelcoat chip repair

    Have a 89 Cobia 265 FC. Its setup as a great lakes fishing boat so it doesnt have to be 100% perfect, but I'd like to start tackling some gelcoat repairs. I've done everything from regular maintenance to complete stringer replacements, but gelcoat has me a little stumped. Would like to start...
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    1989 5.7 350 Mercruiser ignition replacement help - possible upgrade to DUI unit

    Here are pics of the completed install. It really cleaned up the back of the motor. Shift interrupt (white/green) hooked into the tach wire coming out of the main harness and purple hooked into the + side of the Davis unit.
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    Boat switch panel and mystery button

    Ah yeah that would make sense. So how does it actually work since its measuring 12v across the terminals as is right now? And what is the best way to get rid of it? Is it just a matter of splicing the wires together?
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    Boat switch panel and mystery button

    It does match all of the factory buttons and design. I guess it could have been a blank space that someone added something to.
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    1989 5.7 350 Mercruiser ignition replacement help - possible upgrade to DUI unit

    I did end up going with the Davis Unified unit (ended up having to buy 2 of due to Fedex "delivering" the first one when it actually wasnt. Before the install I also upgraded the shift interrupt to the new style with the bracket. Didnt realize my shift interrupt hasnt been working for awhile...
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    Boat switch panel and mystery button

    The boat is a 1989 Cobia 265fc. On the switch panel with the ignition, blower, and horn there is a mystery button that Im not sure what it does. The button isnt fused and seems to have a constant 12v to it. I have to take some of the boat apart in order to trace the wires going to it, but...
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    1989 5.7 350 Mercruiser ignition replacement help - possible upgrade to DUI unit

    The plug that goes into the timing advance module on thunderbolt IV system on the passenger side riser - mine is the v8-22 version.
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    1989 5.7 350 Mercruiser ignition replacement help - possible upgrade to DUI unit

    Just got back from the boat with some updates. I started right up and timing at high idle was 9 degrees. It ran for awhile but it was rough. Tried to go back to normal idle and the boat cut out and then wouldnt restart. Its the same issue I had last year that I fixed by messing/cleaning the...
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    1989 5.7 350 Mercruiser ignition replacement help - possible upgrade to DUI unit

    That actually the trim unit power - i had the trim tied up and out of the way and had it disconnected when I was glassing. That was a pic from years ago.
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