Heat Exchanger Inspection at Winterization Time . . .

[tpenfield]

Today was winterization day for my twin Mercruiser 7.4 LX MPI with Full Closed Cooling (never understood what the 'LX' was for . . .) Anyhow . . .

I pumped out the gasoline (44 gallons) and mixed up about 7 gallons of 'fogging cocktail' and added it back to the tank. The rest of the gas goes to the cars.

I set up my 'bucket-to-earmuffs' contraption that I use for winterization.


There were similar deposits in 2016 when I inspected and cleaned them. The salt-away does not seem to do much with these deposits; you really need to open the H.E. up and scrape the deposits away. I think the 6-7 holes that tend to get blocked represent about 15-20% of the cooling capacity. So, it is a good thing to check your Heat Exchangers often, if you run in salt water, as I do.

:thumb:

 

[alldodge]

The 7.4 mpi lx is 330 hp (oval port heads), the 454 mpi is 383 hp (rectangular port heads)

The L29 is 310 hp

 

[alldodge]

Here is what BUP post a while back

carb was 300 hp
carb HO was 350
mpi 310
mpi LX 330
mpi HO Mag 385

 

[harringtondav]

I don't know the plumbing of your heat exchangers. Is it possible to isolate the raw water side and fill them with 5% Acetic acid (AKA white vinegar) after your other process, and let them soak? Maybe properly diluted Lime-Away or CLR, or coffee maker cleaner? The HE tubes appear to be copper, which the latter three products claim to not harm. In fact it looks like you'd just have to put enough of this kind of stuff in to submerge the bottom 1/4 of the exchangers. This could clean out any other calcium deeper in the tubes. Then do a second fresh water flush on the HEs.

BTW, this looks like the boat you're planning to put under your homemade gantry (?). That looks like a kinda hard surface you're parked on. Maybe hard enough to avoid plywood strips to roll that gantry over the boat.

........maybe a half dozen bottles of that Sam Adams you have on your swim platform would clean the crud from a HE

 

[tpenfield]

The 7.4 mpi lx is 330 hp (oval port heads), the 454 mpi is 383 hp (rectangular port heads)

The L29 is 310 hp

I had always thought that my engines were 310 HP. They are "Gen 6" 454's . . . still not sure what the "LX" in the model # stands for , if anything in particular.

Here is my model number, based on my serial numbers:

MERCRUISER

1996

7.4LXMPI

474L118JT

7.4 LX (EFI-MPI) BRAVO (GEN VI)

 

[tpenfield]

I don't know the plumbing of your heat exchangers. Is it possible to isolate the raw water side and fill them with 5% Acetic acid (AKA white vinegar) after your other process, and let them soak? Maybe properly diluted Lime-Away or CLR, or coffee maker cleaner? The HE tubes appear to be copper, which the latter three products claim to not harm. In fact it looks like you'd just have to put enough of this kind of stuff in to submerge the bottom 1/4 of the exchangers. This could clean out any other calcium deeper in the tubes. Then do a second fresh water flush on the HEs.

BTW, this looks like the boat you're planning to put under your homemade gantry (?). That looks like a kinda hard surface you're parked on. Maybe hard enough to avoid plywood strips to roll that gantry over the boat.

........maybe a half dozen bottles of that Sam Adams you have on your swim platform would clean the crud from a HE

In order to do an acid soak/flush, it would be best to remove the HE's from the engine and fill them from one end (probably the in/out end) and let it soak the anode end of the HE. I removed the HE's and used a variety of solutions (CLR, KaBoom, etc.) in 2016. Back then, I still had to scrape away the calcium build-up, but I think it did an OK job on the tube internals.

Last year, I did the salt-away flush (10% salt-away in 5 gallons of water), same as this year, but it looks like it does not do much for the calcium build-up.

Yes, that is my boat that will be needing the gantry for engine pulls. It is in its usual spot in front of my garage on a paved driveway. The beer selection would be Redbridge or several other other 'gluten-free' varieties.

 

[achris]

. . still not sure what the "LX" in the model # stands for , if anything in particular....

I think it's just a hangover from the bad old days of carburettors.. it was a distinction between 2bbl and 4bbl. Then EFI came along and messed that up. With the V6s they added LXH to cover the TBI engines. With the 3 litre is was the distinction between the 140 head and the 120 head.

Then MPI came along and that whole L/LX thing was dead, but they couldn't come up with new letters (except MPI), and wanted to continue the distinction between the different outputs of the same size engine, so the LX stuck...

Chris.

 

[tpenfield]

AllDodge I checked the operator's manual that I have in the document set that came with the boat.

You're right - 330 HP I think the full inboard model is rated at 310HP (prop shaft) I am so excited to have the extra 20 HP !!!



Still not sure why they call certain models "LX" though . . . :noidea:

 

[alldodge]

I am so excited to have the extra 20 HP !!!

Don't let it go to your head, with great power comes great responsibility :rockon: and that's 40 hp

 

[garbageguy]

That's a great boat, sorry to see you're out of the water for the season - my mechanic and I are putting that off (my son is out of town). Thanks for sharing your winterization process with great detail and pictures - makes me wonder what the rest of the story is

 

[tpenfield]

That's a great boat, sorry to see you're out of the water for the season - my mechanic and I are putting that off (my son is out of town). Thanks for sharing your winterization process with great detail and pictures - makes me wonder what the rest of the story is

Well not sure there is a rest of the story, except I try to make winterization as easy as possible. Full closed cooling is a lot easier to winterize, IMO, because there is less to worry about. Just the intake side, oil coolers, HE, and exhaust elbows.

My bucket contraption makes things easier, rather than running the hose straight to the earmuffs. I can run water into the bucket for the warm-up and fogging, then stop the water, let the bucket drain down and add the AF. . . all without turning off the engine. Of course with 2 engines to take care of, you look for time savers.

Some may wonder why I bother to run AF, instead of just draining the raw water side. I have sea water strainers on the intake side - they hold about 12 oz of water and are nearly impossible to reach. So, instead of disassembling & draining them, I run AF through. I did the same on my previous boat, but used only the -50 F pink stuff. Each year, I would see that the sea water strainer 'jar' would be cracked. The -50 F stuff is a pipe burst rating, but clearly not sufficient for the plastic of the sea water strainer. We would get a few -10 F days (or colder) over the winter and that was enough to partially freeze the AF and crack the sea water strainers. It took me a couple of years to figure out that the -50 AF was causing the cracking.

On this boat, I have used the -75 or -100 versions of the AF so that the sea water strainer would get a little extra protection. I only need a couple gallons of the higher rater AF to more than reach the sea water strainers, since they are the first thing along the intake hose. So, I run 3 gallons of the cheap stuff in the bucket, and as that is nearly gone, I pour in the good stuff and keep running the engines until it has all gone in. Seems to work, I have not had to replace the strainers since using a couple gallons of the good stuff at the very end.

I suppose, I could use just the -75 F stuff since it is only a few $ more per gallon. When I was using the -100 F stuff, it was crazy money . . . $15/gallon, so I only bought what was really needed.

I still drain the Heat Exchangers, because that is big money if they ever froze to the point of breaking.

Next year I may have to figure out a way to flush the HE's without disassembly. Apparently a hydrochloric acid solution can do the trick. . . not sure the CLR is strong enough to get rid of that much calcium. The HE's are made of copper, so whatever I use will need to be compatible with that type of metal. I'll have to see how much build-up happens just after 1 year, since I did not check for 2 years.

 

[harringtondav]

Next year I may have to figure out a way to flush the HE's without disassembly. Apparently a hydrochloric acid solution can do the trick. . . not sure the CLR is strong enough to get rid of that much calcium. The HE's are made of copper, so whatever I use will need to be compatible with that type of metal. I'll have to see how much build-up happens just after 1 year, since I did not check for 2 years.

Muriatic acid is hydrochloric acid. I notice many consumer swimming pool cleaners are also basically the same. I'm pretty sure that w/o dilution muriatic acid from the jug will corrode copper fairly quickly. Maybe get some scrap copper tubing, and experiment with various dilutions until you get it thinned to a 'safe' level. One that doesn't corrode w/in 2-3 hours. Then see how long an eggshell or other high calcium solid lasts in that same mix.

 

[Walt T]

Personally I would not try to run any fogging oil through a fuel injected engine. TBI is okay in my opinion but the MPI system isn't built for oil in the fuel. Those injector orifices are pretty small and were not intended to inject oil. Just my opinion

 

[tpenfield]

Personally I would not try to run any fogging oil through a fuel injected engine. TBI is okay in my opinion but the MPI system isn't built for oil in the fuel. Those injector orifices are pretty small and were not intended to inject oil. Just my opinion

You should certainly take this concern up with the engineering staff at Mercury/Mercruiser, as their MPI fogging procedure calls for a 10% 2-cycle oil/gasoline mix, run through the engine.

 

[Lou C]

Ted interesting pix of the heat exchangers. Future project for me when I eventually re power. Would love a new boat but bought 2 new cars in the last couple of years lol...not for me tho still driving the old Jeeps ...
I know what you mean about the -100 AF great stuff but very price ($15) if not on sale ($11). I have been using a cheaper alternative....Sierra propylene glycol AF; that is $14 a gallon but you mix it with water 50/50 and that gives you freeze protection down to -26 and drops the cost to $7 a gallon. You could go 60/40 if you want -40 freeze protection but the coldest we get is zero so -26 is fine. They sell it at Ace Hardware at least here in NY.

 

[Lou C]

I tested what I mixed up in the freezer at the coldest temp it will reach (-5–>-8*F) and it’s totally liquid at that temp....

 

[tpenfield]

Thanks for the advice, Lou :thumb:

I thought you did recently rebuild the engine in your boat.

I used to have to special order the -100 AF. We get to about 0 F on Cape Cod, so the - 75 seems to be plenty. I’ll keep an eye out at Ace Hardware next year.

At some point the HE’s will probably need to go out for a professional cleaning.

 

[Lou C]

Did a top end overhaul with re man heads but kept the old short block. So far so good but the short block is 30 years old!

 

[Scott Danforth]

Ted, most local radiator shops can clean HX's

 

[tpenfield]

Ted, most local radiator shops can clean HX's

I also Googled some videos of cleaning marine heat exchangers with a Barnacle Buster (& water) solution. It looks like it takes care of the heavy build-ups, etc. So, I may try some of that each year, so I don't have to open up the heat exchangers as often.