Mercruiser 350 MAG overheating

[Mauro Brisola]

140 hours / 3 years raw water cooled 2013 350 MAG started to work with high than normal temperatures. Used on salt water. Depending on the boat load and the rpm temperature is "under control". Used to be steady about 163 F before. Now with low load (3 persons) and up to 3500 rpm temperature will be about 168/172. Can navigate hours this way. But with higher load or speed it could tend to aproach alarm zone (194 F). Problem is getting worse every time boat is used.

Engine oil is clean.

My bay "playground" has some tricky sand shoals. Then sometimes the drive unit "eats" some sand. Because of this I thought problem was raw water bad pump rub impeller related. But after dissassembling raw water pump I found the impeller in good condition.

Is possible to see too much corrosion. The iron water tube that goes under engine front is with a small corrosion capillary hole. It is possible to see water droping by one of the numbers.

After dissassembling this hose under engine front there was o lot of corroted metal "leaves" (picture). Is it "normal" to find it in a 3 years / 140 hours engine?

Despite engine is flushed with fresh water after every day trip, probably marina people did not flush well sometime(s).

My doubts:

-Considering this situation what's the most likely cause for the overheating? A bad circulating pump? Some clogged hose/place? Where?

-Have I to be much worried about the mufflers and risers condition?


Thank you for your input.

 

[alldodge]

Start first with checking for Bravoits. Bravoits is where the hose coming thru starts swelling and can close off the line. Need to remove the hose and fitting coming from the transom and going to the sea water pump. This is what a bad Bravoits looks like

 

[Scott Danforth]

Also check the exhaust / risers for severe rust

 

[Mauro Brisola]

Are 3 years enough to Bravoitis development? Boat first use was in Jan 2014.

I read something about checking raw water flow restriction / raw water pump system flow by measuring the water flow connecting raw water pump outlet in a bucket.

Are this test enough to eliminate the raw water restriction doubt?

 

[alldodge]

In most cases it takes longer then 3 years, but this has been an issue with salt water boats. It could also be you have something stuck in the intake hose. Tpenfield here on iboats had a small sea shell stuck just in side which caused it to heat up some, didn't overheat but was a pain to tract down.

If the exhaust flappers broke off it can cause a bit of over heat but also can cause a reduction in power. Do you have the 7 point or 3 point drain system? The 3 point can cause issues if the check valve or other components are restricted.

You probably know this just covering all basis. Your type pump also uses a different impeller 47-8M0104229 then the Gen 4/5 47-59362T1. How does the back of the pump housing look, where the hoses attach? If there are grooves it may need a stainless wear plate. Many folks have experienced the pump not work as good after impeller replacement.

 

[Scott Danforth]

Are 3 years enough to Bravoitis development? Boat first use was in Jan 2014.

I read something about checking raw water flow restriction / raw water pump system flow by measuring the water flow connecting raw water pump outlet in a bucket.

Are this test enough to eliminate the raw water restriction doubt?

at 1000 RPM, the raw water pump should fill a 5 gallon bucket of water in about 16-20 seconds.

 

[Mauro Brisola]

No Title

Thanks for the answers. I'm in the process of learning about the DIY regarding my 350 MAG with Bravo lll. Working 25 years with cars repair I hope I can do better than local Mercruiser repair people. I'm in Brazil.

Answering my own previous question: "Yes. It is possible a 3 years boat to develop (severe) Bravoitis!"

After taking the 2 bolts raw water transom plastic connection I found the hose end and the plastic insert in a very bad shape. What explains the engine temperature rising tendency. Picture angle are not good because engine is in place.

Now I have to deal with it. No matter if with original Mercruiser parts or not, have I to remove the outdrive in order to repair this problem???

 

[bman440440]

yupp that's bravoitis.... IMO I would get the block off plate for the transom and install a threw hull hi-speed pickup with a sea-strainer and be done with it

 

[alldodge]

You don't need to remove the motor to fix it. I installed the new style tube to prevent it from happening last year on my Rinker. Used Merc part number kit 32-8M0090859

http://forums.iboats.com/forum/engi...ard-engines-outdrives/10246284-bravo-itis-fix

 

[Hoosmatroos]

Yes possible but not an easy job. Hard to get to the lowest bolt. Didn't suffer from Bravoitis but replaced it anyway and finished it yesterday. Greatest day of my life

 

[jmarines]

I just didn't his fix also.. i use the hardin kit. If I were to do it again I would probably go with the mericruiser kit.