Heads Up--Mercruiser Fuel Cooler Corrosion Issues

[fwebster]

Here's a heads up for you Mercruiser owners who have the new style block type fuel cooler on Mercruiser engines. There have been at least 3 versions of the fuel cooler, the problem child is called "Kool Fuel 3". Previous versions, Kool Fuel 1 & 2 are not affected. The one to watch out for is a rectangular black box about 9-10" long X 4-5 " wide and 6" high with a 2 hose manifold attached by a center bolt for the cooling lines. The same part is apparently used on both 8.1 and 6.2 engines, but I don't know if 5.7's are involved. Diesels are not affected.

The problem is that to cool the fuel, engine coolant cannot be used because it is too hot. Mercruiser runs sea water through the fuel cooler because it is usually under 80 degrees F. In their infinite wisdom, the Mercruiser engineers have designed Kool Fuel 3 to be made out of aluminum. When Sea water is left in the fuel cooler, the salt attacks the aluminum and the ensuing corrosion blocks the inlet and outlet line orifices. With the orifices blocked, the fuel delivered to the engine is too hot and the engine will shut down. Typically, the engine may run for a couple of hours then either shut down or fail to restart after being shut down.

Once corroded, there is no fix other than to replace the fuel cooler. The cost is about $800 ea. Mercruiser is paying dealers about 1.5 hours labor for a replacement, but most are taking a lot longer. I saw one changed last week on an '07 38DA and it took the mechanic 4-6 hours on the port engine where the cooler is low on the outboard side. An out of warranty repair could easily get to $1500.

This only affects boats used in salt or brackish water. The only avoidance measure is to begin flushing your engines even though they are FWC. The shop foreman at our marina recommends using a neutralizer like Salt-Away.

I saw a stack of about 15 bad Kool Fuel 3's removed under warranty awating shipment back to Mercruiser, so this isn't a little issue for them. Hopefully, Mercruiser wil realize that they "pulled another one green" without adequate testing (or thought!) and a redesign will come soon.

In the meantime, start flushing and good luck.............

 

[Dave S]

My 350 Mag has that type of a fuel cooler. I wonder if the aluminum tubing on those coolers might also be subject to electrolysis corrosion issues? I don't boat in Salt Water but I will still talk to my dealer about the issue to see what I can find out. By the way, for all you folks who have one of those coolers, don't be shocked at the near $50 dealer price tag for the fuel filter element. :wow:

 

[skolbe]

Wow - Mercruiser R&D is unbelievable.

 

[Morpheus]

Here's a heads up for you Mercruiser owners who have the new style block type fuel cooler on Mercruiser engines. There have been at least 3 versions of the fuel cooler, the problem child is called "Kool Fuel 3". Previous versions, Kool Fuel 1 & 2 are not affected. The one to watch out for is a rectangular black box about 9-10" long X 4-5 " wide and 6" high with a 2 hose manifold attached by a center bolt for the cooling lines. The same part is apparently used on both 8.1 and 6.2 engines, but I don't know if 5.7's are involved. Diesels are not affected.

The problem is that to cool the fuel, engine coolant cannot be used because it is too hot. Mercruiser runs sea water through the fuel cooler because it is usually under 80 degrees F. In their infinite wisdom, the Mercruiser engineers have designed Kool Fuel 3 to be made out of aluminum. When Sea water is left in the fuel cooler, the salt attacks the aluminum and the ensuing corrosion blocks the inlet and outlet line orifices. With the orifices blocked, the fuel delivered to the engine is too hot and the engine will shut down. Typically, the engine may run for a couple of hours then either shut down or fail to restart after being shut down.

Once corroded, there is no fix other than to replace the fuel cooler. The cost is about $800 ea. Mercruiser is paying dealers about 1.5 hours labor for a replacement, but most are taking a lot longer. I saw one changed last week on an '07 38DA and it took the mechanic 4-6 hours on the port engine where the cooler is low on the outboard side. An out of warranty repair could easily get to $1500.

This only affects boats used in salt or brackish water. The only avoidance measure is to begin flushing your engines even though they are FWC. The shop foreman at our marina recommends using a neutralizer like Salt-Away.

I saw a stack of about 15 bad Kool Fuel 3's removed under warranty awating shipment back to Mercruiser, so this isn't a little issue for them. Hopefully, Mercruiser wil realize that they "pulled another one green" without adequate testing (or thought!) and a redesign will come soon.

In the meantime, start flushing and good luck.............

Would this be on a 5.0MPI Mercrusier engine?

 

[estebanj]

Is there a link to a press release or recall?

I'm not questioning the info; just want hard copy for my files.

Esteban

 

[fwebster]

I don't see how galvanic corrosion could occur since the manifold is only in contact with the the aluminum fuel cooler.

Mercruiser's usual practice is to just re-invent around a problem and issue a different or superceded part when a replacement is ordered. Do not expect them to issue a recall (this isn't safety related), press release (advertising their mistake) or a tech bulletin (thus opening the warranty claim flood gates). If you have a failure while under warranty they will replace it, for now with another aluminum one that will fail just like the first one only later. If your failure occurs after your initial warranty, my guess is that you are going to be on your own unless you raise enough hell to get someone's attention.

As far as what models, years, engines are affected, I posted pretty much all I know. If you have questions, I'd suggest you go to the service manager at your Sea Ray/ Mercruiser dealer and ask them to show you a Kool-Fuel 3 and see for yourself if you have one. If you do, then I would ask the dealer to inspect yours and see if you have corrosion before your warranty expires and, as I said, begin flushing the sea water side of your cooling system immediately.

My purpose is only to make forum members aware of a potential problems I see when I'm around boats that may affect them. Sorry I'm not more help.

 

[Turtlesboat]

Frank is the man. I don't think I have an issue but i'll be checking.

 

[BON DIA]

Thx FW for the heads up...shouldn't affect BD but I'll ck verison of fuel cool anyway.

 

[topgun1185]

Wow I had no idea I have 2005 350 mpi with kool fuel 3. I am still under warrenty. I will check it out this spring.

 

[2000SEARAY280SS]

Frank,

Is this a picture of the unit in question?

edit:

From the feed back this is not the kool fuel 3 unit in question it is a gen III.

 

[topgun1185]

Mine looks similiar but is not the same I think you may have an older cool fuel model.

 

[Stray Cat]

Is this a picture of the unit in question?

That looks like the Generation III module, and depending on your engine / bilge layout are a pita to get at.

 

[fwebster]

I'm not an expert on gas engines by any means....I was just letting you guys know about the problem.

I believe that the 2 earlier versions were long tubes made of brass and looked more like a heat exchanger. Kool Fuel 3 does look like the photo, however, by now Mercruiser may have redesigned the unit and the 4th iteration may look just like ver. 3.0.

Check with your Merc dealer to be sure.

 

[280 SeaRay]

Thanks Frank for the information. No fuel cool here... whew

 

[Bridog]

That looks like the Generation III module, and depending on your engine / bilge layout are a pita to get at.

Jeff, Is the 300DA with 350's included? I wont see the boat for another 2 weeks. Thanks for sharing that info Frank. Brian

 

[Weave]

Jeremy...are you sure you dont have it? I am 99.9% that my 4.3MPI has it........Read about this and was warned about it from another forum.
Thought it was common knowledge. Guess never hurts to share something:smt021

 

[blueeyeboatr]

Guys,

So what does the Kool 3 look like and how can I tell if my 2005 320 Sundancer wit 350 MPIs v drives has it or NOT.

Thanks

 

[lady haggis]

Hi Frank...We live in Bermuda and have a 400 c Harbour Master w/2 8.1 Horizons .
Both engines quit on sunday...and would restart for a few mins only..
we have been away and boat not used much in last 4 months.
Mechanic baffled so....thought sensors ,mal function.
Searched the web for any problems w/these engines and found your posting! Thankyou!!!!
removed both yesterday...total crusted w/salt...uptake pumps quit working...so engine starved for gas.Mercruiser did not admit problems with theese units but are shipping us 2 new ones today.
Hoping this will get us out on the water this weekend! Bermuda is experiencing amazing boating weather this week!!
Thankyou u again...withoout ur post we may still be looking for problem and also dishing out the $1600 for new units.
Enjoy your day....

 

[fwebster]

lady haggis,

Glad to help. Sometimes I run into bits of information like this from friends who repair boats and here is another one: With your engines, you should probably search this site for another "Head Up......" posting I did on aluminum exhaust manifolds.

http://clubsearay.com/forum/showthread.php?t=6038

You don't mention your model year so I don't know if your engines are affected or not. This one is, more serious because not knowing or finding it in time usually means you fill an engine with salt water and the repair cost of replacing not only manifolds but a new 8.1 is significant. This is also another one where Mercruiser is doing an "Animal House" recall.....you know, a double secret probation style recall. If you work thru your dealer Merc is replacing manifolds and even some damaged engines.

Hope you don't have them, but if you do, replace them now.

 

[tgfreeman@hotmail.com]

I also have a 2007 Harbor Master 400C with twin 8.1S Horizons. After 18 months of having one or both engines quit two or three times a day, Mercruiser has almost admitted there is a problem with the Gen III Cool Fuel Module. They want to run a borescope into the cooling chamber to see if it is a corrosion problem. Be very careful of this problem. The technician monitored the gas temperature and found it to be over 120 degrees exiting the fuel pump after only five minutes of running the engine!