Finally gave up on Merc 496 Mag overheating

[Ladsm]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

 

[Bigbore500r]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

View attachment 1268055

Ewww....
Ex Girlfriend, dat you?

 

[TrollerDave]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

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What is that? TStat housing?

 

[rrrr]

What is that? TStat housing?

Whatever it is, it swallowed the bait and the hook.

 

[Orange Juice]

Whatever it is, it swallowed the bait and the hook.

Sucked the entire impeller inside out.

 

[OCMerrill]

Underneath the intake hose connector at the drive.

They can corrode and get funky causing a restriction.

 

[Ladsm]

Its at the connector on the transom plate. They are pulling the motor today to clean it all out and replace the hose. I did the other end on the outside of the boat at the gimble ring last summer.

 

[96motorhead]

What is the fix for this?

 

[SoCalDave]

What is the fix for this?

See post 7

 

[wet hull]

Its at the connector on the transom plate. They are pulling the motor today to clean it all out and replace the hose. I did the other end on the outside of the boat at the gimble ring last summer.

I had that same thing happen, we opted to do a block off plate and go through hull with a sea strainer. Motor got to stay in boat.

 

[MR HARLEY]

What is the fix for this?

A Merc 1100.

 

[shunter2005]

Its at the connector on the transom plate. They are pulling the motor today to clean it all out and replace the hose. I did the other end on the outside of the boat at the gimble ring last summer.

Just curious, but is your boat fresh water only or do you hit the salt as well?

 

[Havasu Catman]

It is caused by storing your drive in the up position. I posted this in the drive storage position thread.

Store them down. When stored up water is trapped in the drive and starts to corrode at the transom. It will restrict the water flow to the engine over time. You will have an overheating condition under high demand (full throttle). It will get worse over time and restrict more. Do a search for the word bravoitis and you will see what I am talking about. If you store the drive down you will slow or not allow this process to take place.

 

[Havasu Catman]

I had that same thing happen, we opted to do a block off plate and go through hull with a sea strainer. Motor got to stay in boat.

If you install a block off plate make sure you remove the hose to the transom or cut a hole in it to let the water force feed and flow. The water passing through the drive is necessary to cool the oil in the drive. The water from the drive is not just to cool the engine. I have seen many Magic decks with 525's rigged from the factory with an offshore water pick up and a block off plate on the transom. The XR drives ran hot and by 200 hours the upper gear set would pit and break a tooth causing catastrophic damage.

 

[HubbaHubbaLife]

@Shlbyntro to the fuckin phone already

 

[Shlbyntro]

fwiw the engine does not have to be pulled for this repair. the job is much easier without it there, but it is not a necessity.

More 496 MAG cooling questions- Update, found the blockage!!!

I started a month ago with sucking up some sand and then the mercruiser alarm would go off at low speeds. I flushed the seawater lines and replaced the fittings on the bottom of the exhaust manifolds with the little white balls because they were corroded and plugged. That didnt make much...

www.riverdavesplace.com

 

[Chili Palmer]

This happened on my 496HO, Brian at BD Marine installed a blocker plate and an offshore pickup at the base of the transom and no more troubles.

 

[wet hull]

If you install a block off plate make sure you remove the hose to the transom or cut a hole in it to let the water force feed and flow. The water passing through the drive is necessary to cool the oil in the drive. The water from the drive is not just to cool the engine. I have seen many Magic decks with 525's rigged from the factory with an offshore water pick up and a block off plate on the transom. The XR drives ran hot and by 200 hours the upper gear set would pit and break a tooth causing catastrophic damage.

Mechanic did all of that, I remember him mentioning this and also saying it would form unwanted pressure inside the drive. We did it about 4 years ago now. Not sure what its called but the kit from Teague required a hole tapped in side of the upper where a u shaped fitting went in. It takes that water pushing though drive and sprays onto outside of upper. He put that on as well.

 

[Jay Dub]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

View attachment 1268055

same thing happened to our 255. Barrett fixed it with a Teague kit without removing engine and without replacing transom assembly. Its basically a block off. Then you add an external water pickup and sea strainer.

 

[Shlbyntro]

if you take the bell housing off the transom assembly, there is ample room and access to clear out the section of transom that has corroded and closed in without removing the engine or the transom assembly. Merc makes a hose update kit where the part of the hose that passes through the transom is a hard section sealed with a grommet and clamp as opposed to the interior expansion insert.

As for that drive kit for a block off plate if you were to go that route, it is not needed. Just remove the hose from the bell housing and the water from the drive will exit to the front where the bellows are. everything up there that needs protected from the elements is already sealed up. Any heat generated from the drive into the water passing through it isn't anything compared to the exhaust water that exits in that same location with the "performance" exhaust bellows anyway.

 

[HBCraig]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

View attachment 1268055

Its at the connector on the transom plate. They are pulling the motor today to clean it all out and replace the hose. I did the other end on the outside of the boat at the gimble ring last summer.

Mine did this 3 years ago. Savage Marine did mine. He's an expert at this. Pulled my drive and engine, replaced and had it back to me in 8 hours.

 

[Ladsm]

Just curious, but is your boat fresh water only or do you hit the salt as well?

Fresh water only, mostly Havasu, Parker and Lake Mohave. I actually heard running it occasionally in Salt Water actual helps clean out the cooling because the salt water friction scrubs out the corrosion.

 

[Ladsm]

fwiw the engine does not have to be pulled for this repair. the job is much easier without it there, but it is not a necessity.



View attachment 1268399

More 496 MAG cooling questions- Update, found the blockage!!!

I started a month ago with sucking up some sand and then the mercruiser alarm would go off at low speeds. I flushed the seawater lines and replaced the fittings on the bottom of the exhaust manifolds with the little white balls because they were corroded and plugged. That didnt make much...

www.riverdavesplace.com

You were absolutely right, I followed all the steps people mentioned, changed the Sea Water pump with the rebuildable stainless Hardin pump, Flush the hoses, clean the oil cooler, clean the heat exchanger, changed the T-stat that was bad only it stuck open so it probably helped the situation. On my boat its nearly impossible to get to anything behind the motor so I decided to take it to a shop that had a lift capable of getting the Big Block lifted up. I wasnt confident my HF engine hoist was up for the job. Hoping to be on the water this weekend.

Everytime I opened up a new hose or cooler I found issues so I kept thinking this has to be it???? I am confident now I will actually see 160* after every piece of the cooling system has been freshened up.

 

[mash on it]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

View attachment 1268055

How many hours on this boat/motor?

Dan'l

 

[Ladsm]

How many hours on this boat/motor?

Dan'l

530ish and I do store it with the drive down like others mentioned.

 

[LazyLavey]

Quagga.....

 

[F.U.IRS]

I posted up a couple threads looking for advice and followed everything but still overheated under load. I finally took it to Absolute Speed and Marine in Havasu and sure enough I caught a bad case of Bravoitis!!!!!

View attachment 1268055

Must be going around, just had mine done too

 

[HBCraig]

530ish and I do store it with the drive down like others mentioned.

Mine was done at about 450 hours. I store with my drive up

 

[rush1]

What is that? TStat housing?

Its the intake hose going through the bravo housing that feeds your raw water pump . this happens all the time on bravo3 outdrives used in salt water.