Heads Up--Mercruiser Fuel Cooler Corrosion Issues

Thanks for the info on this. I'll be checking Mercruiser for a check on my newish (2007) 6.2 HO engine. I do flush after every dunking but knowing the kooler can go south, I'll be asking for a better unit...
 
FYI - I can speak for my 8.1L MPI's. They were manufactured Spring 2003. Some of the models came with inline coolers (tubular) whcih ran the fuel line thru it. The fuel filter is seperate and an in-line filter prior to the water seperator.
Other engines manufactured had an option based on certain years that had the Fuel Cool - Gen III unit. It is a small box looking assembly that included a drop in fuel filter assembly screen. Thats all I can add to this topic.
 
Add me to the cool fuel corrosion list. Luckily it's covered under warranty. I hope they replace it with a better unit. As Frank said...anyone with this unit should have it checked out before the warranty expires.
 
Here's a picture of my Kool Fuel (Not sure it's a #3) leaking. The boat has been in service (in salt also) for approximately 1 year. Now the raw water delivery system is leaking. I guess Merc needs a picture of it leaking before they will replace the delivery system. I understand that if they see corrosion in the unite, they will replace the whole thing. If not, I think they might replace just the delivery hose assembly. Sounds like a B/S temporary fix that I will have to deal with later. Thanks Merc.!!!

CIMG0028%20%28Large%29.jpg



Kevin
 
Has anyone been able to get Mercruiser to help with the Cool Fuel Gen III Module AFTER warranty has expired? I have encountered this issue this season on a motor installed in 2006. I had to replace the cooler at a cost of $800.00. My initial contact to Mercruiser, via email, indicated that the Service Bulletin #2009-01 was to inform dealers of a new design for the module. I want to pursue Mercruiser further as I had to have the entire module replaced because of the corroded hose fittings. If I had the new design, only the fittings would need replacing.

Please, any experience with Mercruiser on this issue would be extremely helpful. Let me know.
 
based on this thread, my issues with hot no starts, and in general fuel BS since 2007, today I pulled the Port engine Cool Fuel assembly. My engines are 1998, and by everything I can find in the merc service lit, the Cool Fuel is Gen II. This is for a 380Hp 7.4 Mag MPI series. The outside is seriously oxidized, but perhaps not corroded. I had enough issue with the Port engine last week to warrant the pull. I found that the o-ring on the return line vacum fitting was not as pretty as I would expect, and so far the rest looks ok, save the green crust. This weekend will be the big cleanup, and search for whatever filters are lurking inline with the fuel pump and heat exchanger. I will figure out how to pressure test this to see if raw water is seeping into the fuel line. My symptom is Port engine won't stay running, and when it does, the computer is all over the place with the throttle, and when it does run for a bit, the exhaust smells like old lawn mower gas, even though it's pretty new, at least for 3/4 of the tank. bad gas? maybe, but the Stbd was filled at the same time, and so far no issues with that tank. water in the cyls? maybe. About to do the full manifold/riser/elbow swap, so we'll see. If you find my old posts, I did replace the fuel shutoff valves right before this new issue. Not hot out yet, so I can't tell if they did any good or not.
 
when you get your gen 3 modules replaced it is a different module. They made the hole larger for water flow and also added the screw in fittings. now if you have a problem you just remove the hose clamps and hoses and you stick a screw driver in hole and clean out the blockage. I've done it many of times.
 
Update: cleaned up the fuel cooler, and reinstalled it. Engine still suffering the same issue. Starts, barely idles, then hunts all over the place, and dies after 15 seconds, or if I try to apply any throttle at all. Got a hold of a Miranda, and found no trhown codes, great fuel pressure, all nominal, except it just wouldn't run. Replaced the spark plugs (had been 18 months or so since the last set). No change. Borrowed a 6 gal tank, and wired it up to the fuel/water sep. BINGO!
So, I've got 75 gallons of contaminated gas. Never underestimate the power of crap fuel.
 
I have these POS on my 09 spec 5.7 MAG Horizons.

My starboard was leaking so bad water trickled into my bilge constantly, 24hours a day(at 200 hours...). I went to take it apart (big nut in photo between the two hoses seen in this thread) it fell apart. The nipples are PLASTIC.

Even worse, the group of morons who designed and approved this didn't notice that simply installing the hose/bracket (which is only sold as an assembly... of course... for $85), crushes the plastic nipples and breaks them. The fit too loosely in the bracket. Mine was undoubtedly cracked the day it was crookedly seated at the factory.

Anyway, when I pulled the nut loose from the bracket, it fell apart. I pulled the broken plastic parts out with a pick, and then scraped the corrosion outward, and cleaned the bore with grease impregnated towel to catch the debris.

Since I didn't want to be ripped off by being forced to buy an $85 hose assembly to replace two $.05 plastic tits (which aren't for sale), I decided to make them out of stainless steel. I am not in the boat business, but I do have a CNC machine shop. I copied the plastic parts, except made them fit the hose bracket properly, and actually interlock.

I have made 100 pieces if anyone needs a pair. I have about 40 sets left. If it will help anyone out, I sell them for a nominal price.

You can cut the two hoses right at the nipples, and you will only loose about 1" of hose. There is plenty of slack to pull the existing hoses onto the new stainless steel nipples.

Hopefully this may help some owners out of warranty avoid the $800 module, and the $85 hose. I can tell you that on my 310, the port module lays against the port bilge wall. You can't slide a screwdriver between it. I am almost sure I would have to lift the engine to change it.

My email is max@traxxion.com

My Stbd runs bad when I cold start... I just joined up to search this forum and saw this post first thing... funny, but not funny.
 
Does anyone make this part aftermarket? It would seem you could hard coat it, or make it from stainless, and it would solve the corrosion problem.

Anyone have a dead one they want to donate to research? I might consider making them if people think there is a demand.

I know I need at least 2!!!
 
I'm actually doiong that at my job. I cleaned out all corrosion on some modules I have and ordered the newer plastic screw in fittings. I'm at mercruiser school this week but when I get back I'm going to try to tap the aluminum housing and see how the fittings fit. I'll let you guys know how it goes and try to take some pics.
 
flflatrate said:
I'm actually doiong that at my job. I cleaned out all corrosion on some modules I have and ordered the newer plastic screw in fittings. I'm at mercruiser school this week but when I get back I'm going to try to tap the aluminum housing and see how the fittings fit. I'll let you guys know how it goes and try to take some pics.
Click to expand...

I would not replace plastic with plastic.

I have made about 50 sets just like the plastic ones, but out of stainless steel.

They fit the clamping bracket correctly and interlock with it.
 
your using the old school bracket that holds the hoses in? I was going to install the new style screw in plastic fittings. I would think that you would have a corrosion issue with using stainless on a aluminum housing. But haven't tried it. if you made 50 of them how are they holding up? and how long have they been in use?
 
Pretty much every aluminum part on a boat is held together with stainless hardware... so I don't know why that would any greater issue than it is any where else on the boat.

There is hardware on the module itself that is stainless from the factory... like the fuel filter cap, etc.

These parts I made push into the bore just like the original plastic ones do. Two square orings side by side like stock. They have a step that interlocks in the hole on the bracket.

The plastic ones don't. They rattle in the holes.

I don't know how to post a pic here, but they are on ebay.

I've sold a handful of sets so far. I mainly made a short run of them since I had to program the machine to make them for my own boat. They have been on my boat for 100 hours, and don't leak and haven't broken. My boat stays in strong salt water all the time.
 
If you look at the fuel filter cap the stainless screws don't go into a water passage. If you look at say where an outdrive is bolted with stainless nuts and studs to the transom assy thats all the places where you see corrosion starting. And the biggest spot would be around the carrier and lower unit right next to the bravo 3 props. Thats why we use zincs which is a weaker metal then the outdrive so it eats them and not the aluminum as much. thats why I was wondering about stainless into an aluminum piece which salt water flows through. it would seem that the aluminum would get eaten quicker then using a plastic fitting that screws in. All of these still get clogged but you can just loosen the hose clamp, pull the hose and stick a screw driver into the hole and unclogg salt build up. At 10 this morning you were asking if anyone does this aftermarket? then then at 9pm you say you have made 50 sets. are you just trying to sell them? if you do make them thats great. Not trying to rain on your parade but trying to get the facts straight. I know doing this is allot cheaper then buying a new module.
 
I was asking if someone had made the entire unit from stainless.

I had already said I made the nipples in stainless.

There's only one nut to loosen to pull both hoses at the same time with the factory arrangement. You don't need to remove the hoses from the barbs, ever once they are made from stainless.

That's actually faster than loosening two clamps and fighting two hoses off of two barbs, and then risking breaking a threaded plastic barb off inside the unit.

The seal is actually made by the orings, not by the stainless touching the aluminum. The Orings are readily available over the counter and cost less than a quarter.

Further, replacing the barbs doesn't require removing the units, putting them on a bench, cutting and tapping threads into the module, and risking getting metal shavings into the unit. That is pretty much beyond the scope of most do it yourselfers.

One way or the other, the aluminum will corrode internally over time. Corrosion around threads will leak long before corrosion around an oring does.

Anyway... other than replacing the unit, there hasn't been an alternative. Mine doesn't leak, and the stainless barbs certainly won't fall apart like the plastic ones did.
 
I found out yesterday that I need the fuel cooler pump assembly changed on my port engine, BUT Mercruiser does not make the original item and has a newer model replacement. You can bet later today I will be at the marina doing much, much inquiring.

Thanks Frank
 
Last edited:
Pseudomind said:
I found out yesterday that I need the fuel cooler pump assembly changed on my port engine, BUT Mercruiser does not make the original item and has a newer model replacement. You can bet later today I will be at the marina doing much, much inquiring.

Thanks Frank
Click to expand...

Please let me know what you find out.
 
Hello Frank,

I have a 2007 320 DA with 350s and V drives. Just splashed today and leaks were apparent at the fuel coolers. It didn't take much research to discover these aluminum units have been the subject of quite a bit of problems. Your posts came up very quickly in my searches. My mechanic has advised me of the considerable $ just to replace them, but this won't fix the problem long term. Is there anything special we have to ask for to get the newer replacement model?

Thanks!
 
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