2012 F40 clogged fuel heat exchanger

[Headhunter]

I could use some help please. We have had this engine since new and it continues to clog the fuel heat exchanger with some type of crystalline substance. The dealer added an inline filter to protect the HX and the filter is clean. Once it happens the engine goes into what I call vapor lock, I will smell fuel and the engine will quit or will not start. Wait 30 minutes and it fire up and will run 4000 rpm all day. Throttle down and idle along for 15 minutes and it quits again. We have just changed the water pump and housing, stat and re-flushed everything. The engine had no codes at the annual service. Yamaha, Atlanta says there is no problem. Any ideas will be appreciated.

[boscoe99]

Are you really referring to the fuel/water heat exchanger or are you talking about the VST filter?

I have heard of many a VST filter being clogged with sodium sulfate but have never heard of the heat exchanger becoming clogged.

Is the heat exchanger freely flowing water? Has there been any talk of replacing the heat exchanger. Have you felt the VST when the problem occurs and is it hot?

What is the serial number of the motor? There was a problem with VST fuel pumps.

Yamaha USA is not in Atlanta. They are in Kennesaw, Georgia. A mile down the street from my house.

[Headhunter]

Yes it is the fuel/water heat exchanger and the serial# is 6BGL1027328. No, I have not felt the vst when the problem occurs. The tell tail gets weak after a long run and continues to get weaker the longer you idle. I added a nmea network so I could monitor the engine temp and it never goes over 160. I know they are in Kennesaw, my kids live in Marietta and I just lump it together with Atlanta.
The dealer has looked at it so has 2 reps from Yamaha and can't figure it out. Billy Mathews form Yamaha suggested I stay out of shallow water with my flats boat even though nothing shows up in the filter. Not sure I need a flats boat for deep water. I am getting ready to pull the F40 off and replace it with a Honda unless I can figure something out..

[boscoe99]

People in Marietta and Kennesaw are usually offended if someone suggests they live in atlanta. I would rather be thought of as being 90 miles south of Chattanooga than being 30 miles north of atlanta.

If the water side of the heat exchanger is being clogged with debris then the fuel won't be cooled as it should. Hot fuel may boil sooner than cooler fuel so perhaps that is what is going on inside your VST. Strange though that you are seeing no debris in whatever filter was installed ahead of the heat exchanger. Keep in mind that a filter will actually slow down the flow of water somewhat. Is the problem better, worse or the same since the dealer installed the filter ahead of the water inlet to the heat exchanger?

Has anyone suggested a different grade of gasoline? Some grades/brands are more volatile than others.

Are you looking for something to suggest to your dealer or are you looking for something that you can try on your own?

[Headhunter]

Agree the fuel is not being cooled when the heat exchanger clogs causing what I call a vapor lock. Had the filter installed at the suggestion of Yamaha, Kenneasaw and ran a number of trips with no problems. Took the boat to the keys and ran it hard for 4 days. Day 4 had the failure. I made it a point to not flush the motor but loaded it on the trailer and dropped it at the dealer. They found the crystalline substance at the cooler inlet. Since the filter was clean they removed it but no one has any reasonable answer or solution to the problem. We do run ethanol fuel in both of our boats. Non ethanol is not a local option here. We do switch brands pretty regularly. Anything either I can try or the dealer at this point is worth a look.

[boscoe99]

Agree the fuel is not being cooled when the heat exchanger clogs causing what I call a vapor lock. Had the filter installed at the suggestion of Yamaha, Kenneasaw and ran a number of trips with no problems. Took the boat to the keys and ran it hard for 4 days. Day 4 had the failure. I made it a point to not flush the motor but loaded it on the trailer and dropped it at the dealer. They found the crystalline substance at the cooler inlet. Since the filter was clean they removed it but no one has any reasonable answer or solution to the problem. We do run ethanol fuel in both of our boats. Non ethanol is not a local option here. We do switch brands pretty regularly. Anything either I can try or the dealer at this point is worth a look.

Was the crystalline stuff found at the cooler inlet on the water side or the fuel side?

[Headhunter]

water side

[TownsendsFJR1300]

Is it salt?

If you pull the lower hose on the cooler (water-exit) and put another hose on it(just or testing), are you getting a fair amount of water flowing thru there?

Almost sounds like not enough flow then engine heat under the cowl solidifies the salt water into solid salt...

[Headhunter]

Scott,
You got to the same place I am, but no one has come up with why this is happening and what to do about it. The dealer pulled the power head and middle section apart and checked all of the water passages and they were clean. We thought there was something floating around in there that restricted the flow after you came off plane but no go!

[TownsendsFJR1300]

is the engine used in fresh , brackish or salt water?

If it was mine, I would taste it (that substance, just a little bit).

I'll bet its salt.

"The tell tail gets weak after a long run and continues to get weaker the longer you idle."

This ^^, should NOT be happening.

The pisser shoud be the same hot or cold at the same RPM. If you can visably see the decrease in water volume I'd try to back track from there.

Being you had the engine since new, possibly the factory left an o-ring seal, etc out. I know a tech had it apart but something obviously is wrong.

I don't know where your located at,but if you can find a Master Yamaha mechanic it might be worth your drive.

Depending on who looked at it, something could have been over looked...

Rodbolt may have some idea's

[formula29]

I had the same problem on my 4.2 300, the heat exchanger on the back of the vst tank was pluged solid with crap! I dont know if it was salt or sand, I would have the same symtoms, if I ran it at speed I had no problem at all, if I idled for a few hours the motor would vapor lock and shut down, pump the ball a few times and it would be fine again.