Why is my BOATS Engine OVERHEATING? Thermostat Replacement

In this video Why is my BOATS Engine OVERHEATING? (Thermostat Replacement) for 2004 Mercruiser 5.7 MAG MPI engine. We replaced our boats Mercruiser 5.7 engine thermostat because it was overheating at speeds around 35 mph at 4500 rpms, and when we slow down it would go back to normal. Can't understand why it was overheating? Thanks for watching! Peace from the Keys!

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#boatoverheating #boating #mercruiser5.7 #engineoverheating #floridakeys #thermostat #keysboatingchannel #mercruiser #Islandparadise #keysbesthangout #happydance #taverniersandbar #saltlife #overheating #keysbestsandbar

[paulmarkland]

Hello there! I just went through the exact same thing you are experiencing with your Mercruiser overheating. I replaced every cooling pump, hose, thermo-stat, exhaust manifold, elbow riser, engine sensor and the problem persisted! It turned out to be the connection that goes through the transom of the boat. The raw water hose the comes in from the Bravo outdrive connects to the raw water hose that goes to the seawater pump on your engine. In the transom of the boat there is a threaded insert that connects the hose outside to the hose inside. Oxidation and debris build up in the passage over time partially clogging and restricting the flow of water through the transom of the boat. There are two choices to fix this: 1. Replace the insert . The part cost about $4. You'll need the part and the extration tool. Problem is actually getting it out. Very limited space behind the motor. It comes out on the motor side of the transom. Plus, Since its connected to the hose in the outdrive you need to remove the outdrive as well to get to the hose connection on that side. I didn't do this. I used option 2: Re-plump the raw water coming in using a new through hull water pickup. I already had a small 3/4" water pickup in the hull for my washdown and live well. I removed it, enlarged the old hole in my hull and installed a 1.25" Groco scoop type water pickup in its place with new ball valves and hoses for about $250 all in. This completely fixed my over-heating problems!

[gm]

A stuck thermostat caused me a massive overheat in the middle of Long Island sound in the dead of night and I could not move an inch. That earned me a one way ticket on Sea Tow back to the dock for the bargain basement price of $500. And since I did not know it was the thermostat at the time I brought it to a dealer who charged me $800 to fix a $40 part. So the moral of the story is make sure you change your thermostat periodically and spare yourself the aggravation and cost.

[Bryan_One]

Not sure if you've changed it yet or not but it sounds like the impeller that's inside your lower unit that helps the motor intake water at speed and if they wear out then the boat can't take on enough water to properly cool the engine and then would slow down it's able to suck water in through the motor with the water pump I know I just had a similar issue

[sharronhumphries]

Thank you for sharing brother !!!. Looking forward for the next video and hopefully a resolution to the over heating issue.

[perfectfitboating]

Man I was hoping the thermostat was the issue. Either way it’s good to change them. Praying it’s an easy fix. Those boats can be money pits but man do we love them! 🤙

[Aksel]

Hello! I have opposite problem... fast ride then engine stays like it has to be, but when idling then one side of exhaust manifold will go hot, but engine is still okay. I will probably take boat out from water and check the impeller in sterndrive... also probably I should check engine water pump. Lets see how it goes.

[alligatorcampers]

Thank you Bro. With your video I saw that my thermostat was misplaced with some monkey. Hopefully it didn’t kill the engine. I started to figure out why wasn’t the gauge showing the temperature. And the hand was only moving slightly when the thermostat opened.

[Supanova]

On closed cooling stern drive boats if you put to much concentrated antifreeze in will it overheat? All passages are clean new pump risers manifolds but temp is 170 this year ntead of 160. Stat is new too. 80 ocean. Thta`s the only thing i can think of. Also guage and sensor new too.

[danielevans]

Lower prop plastic distribution tube was melted on ours and not delivering enough water

[ReelifeFishing]

Pretty cool you know how to dothis stuff. Save a lot of money

[artsirx]

impaler, sound like it broke or some piece broke off and there is a blockage somewhere in the system. had the same issue

[andrewdrevdahl]

I have opposite runs hot at ideal cools down when u get going 1500 plus rpm

[darintraver]

I have winterized my boat for years but this one side drained pink and the other clear ?? I thought thermostat but then both sides would be affected . Any thoughts ?

[joemitchell]

cracked impeller on the circulation pump prevents the water from circulating through the engine correctly

[markdimaio]

Did you say that the housing in 3 years old?

[Drdoomerz]

the 1st guy is probably rite...the insert from the drive through the transom

[andrewdrevdahl]

175 is not overheating check the alarm sender maybe off from gage sender

[jackeagy]

I believe you are using too hot of a thermostat!!! It calls for a 140°f you are using a 160°f. A 140° IS NOT FULLY OPEN until 155° to 160°. A 160°f thermostat is not fully open until 175° to 180°f by then your motor over shots the high temperature LIMIT!!