TOPIC: Classic Mercs lose the battle to Salt Corrosion

Even when the outside of the Merc is cared for with wash downs & protective chemical coatings, the older Mercs will lose the war with salt water corrosion internally.
The attached pictures are of an '81 90hp inline-6 Merc that was reportedly running fine until garaged for a few months.
I came to me seized, but looking pretty decent - except for one 1/2" circle on the port side cover that had been pushed out from salt corrosion.
I struggle to believe the poor beast could run under these circumstances, but I'm telling it how it was told to me.
I have outlined the areas of the inner water-jacket that are eaten completely through, allowing the water to be drawn into the cylinders and slowly destroy the crankshaft & related assembly.
Doc F

I got another salt story for ya all. Doc, think I told ya about it. Volunteer fireman here gave free me a looked pristine newer 5HP 4 stroke. Honda told him it needed a new block, as water gushing out the head? Got it home and found the following. Salt simple ate out the side the head next to the block! As I had zip to lose, I get the pencil grinder out and dug it all out. Kneaded up some "Water Weld" putty, shoved it it, and well, IT HELD and no water out. Not sure if getting full circulation the motor, as tell tale is awful strong, but had it running in a barrel, then on a 12 foot rowboat, and temp gunning it didn't run hot. Damn ya run salt (me)..YA GOTTA FLUSH! I always if not just fresh, vinegar in Saltaway dispenser summer. Let it sit a bit, and flush fresh. Winter, use Saltaway. My old 125 Force on the 20 footer, still runs fine after 20 years!

Heres some pix..

I think that Merc went swimming in the ocean Doc!

That is a common issue with Hondas Robbie, salt water just eats them up yet they will run as strong as Hell. Amazing little engines.

Doc / others....
How much effort / risk / benefit to taking off the water jacket and cleaning out any corrosion or other build up? Does taking off the jacket (I assume that is the big plate on the side) give you enough access to clean out the water channels? I was considering it last year when I had the beast all apart for the paint job and PTT retro fit. Ran out of time if I wanted to get out on the water that season

Peter,
If you are referencing your early 1000, it would be quite an undertaking if it has ever been in salt water.
You would need to lift the powerhead to remove the port side cover & baffle plate, and if a salty, you'll most likely have quite a struggle with the lil cap-screws to keep them from snapping off.
Then you would have very good access to the port side water-jacket areas.
While the powerhead is up, you would probably want to remove the water-jacket cover around the spark plugs too. Another risky maneuver on a salty.
You would want to check & clean the hole for the water to drain out of the bottom of the #6 cylinder while you have the beast up in the air. It is about an 1/8" hole that makes a big difference in whether or not salt particles have a chance to build up in the water-jacket under #6 cylinder.
Surprisingly, Merc stopped putting this hole in the 1000ss block series, and consequently those blocks are more susceptible to corrosion break-through by the lower exhaust port of #6 that will result in water intrusion and permanent destruction.
I drill the hole when I'm building an SS TIGER (1000, 950, 1100)
But,...Once thoroughly cleaned it certainly should add longevity to your cooling system.
I've started having the inside surface of the top cover, the port cover, and outer surface of the baffle plate media blasted and then powder coated to see if this process will slow down or stop salt corrosion, but I am still investigating & unable to make any claims of confirmed improvement.
One of these days I'm gonna blast the water-jackets in the block and if I can get them clean enough apply a powder coating there too before having any of the cylinders, or gasket surfaces remachined for reassembly.
If anyone has already explored this idea, I would love input.
The Mad Doctor Frankenmerc

gfgarland wrote:

I think that Merc went swimming in the ocean Doc!

That is a common issue with Hondas Robbie, salt water just eats them up yet they will run as strong as Hell. Amazing little engines.

I got another older 5 HP Honda from a neighbor that he didn't use anymore as was on his sailboat that sold. Long shaft, perfect kicker on my old Bayliner/Force. He never flushed it much either, and it had to go in the shop for a new oil pan, which salt ate it up. I bought it after that, and its flushed OFTEN!

Well, the story on my Merc is she was only fresh water ever. I've only run it in salt a few times since I've owned it. To get to that salt water I run down a fresh water river for about two miles. So the return trip is about 1 to 1.5 miles going from salt to briny to fresh. The last mile or so is fresh water.

But I have always wanted to see whats up inside the water channels.

Doc, had a friend who wanted to save his merc from the salt and ask me for some input.I can't remember the year but I told him to have any of the water passage areas that were acessable Jet Hot coated. That was 5 years age and He had it rebuilt last year and he was told by the shop that did the work it was one of the best looking engines they had ever seen. Next to none corrosion. He runs this boat out of Vero Beach florida out in the ocean every other day. You might want to look into it some day. Skip.

Very interesting!
Thanks Skip!
If you can track down some sort of link, I would really appreciate it.
Doc

Doc, go to jethot.com and you will be able to see all of there info. I am going to have the inside of the lower unit and mid section coated in this. It should really help keep the carbon/oil build up down.

Thom,
what did the zinc look like on that motor???

Wild Willy!!!!
Good to hear from you - it's been too long!!

Anyway,...There was no lower unit included so I don'y know if they had the right anode or not.
The poor beast came from up your way - Bellingham or Mt Vernon - somewhere around there.

When you get a chance, come on down so we can catch up!
Happy Holidays Pal
Doc F

Doc! Thats a cute lower on the 1250! Anyway, on the anode thing lower? IMO ZIP to do with anything but a LU sitting parked in salt. Thats to be sacrificial used up, before the aluminum gear case. Aint got nothing to do with salt water, sitting to dissolve in the block water motor passages. Salt water damn sure aint battery acid, but when evaporated, and just salt? Theres the problem starting! FLUSH FRESH!...easy to do!

Anyway Doc, on cutting a aluminum prop off? Messed today with some my "how to do it easy stuff" 21 years Machinist, and as any know, ya can't grind aluminum a stone wheel as loads up.
BUT! Did some with a .060 , and and a .160, on a angle grinder, with abrasive cut off wheels. Messed with a block aluminum. Does NOT load up but wears down instead. Way easier then drilling holes, and bust out. Just break off a blade for access the hub. Heres a few pix just took. Hard to see the small blade wheel, but the .160 shows fine. Last is what ya start with first, a 4 inch abrasive on a angle grinder.(PS, Doc as like the idea bronze prop, simple drill and tap studs, for something to "pull on!" Anyway, pix next...

Me again here. ANYTIME YOU EVER GRIND ALUMINUM"? USED A DUST MASK!

Long ago a apprentice Machinist Reynolds Aluminum did the job of polishing the molds that the molds next went molten aluminum, into 50,000 LB ingots then through the mills into coils. BUT?

Breathing Alum dust? Well, its the MAIN ingredient, ANY "under arm deodorant" Simple blocks the skin pores! Look ANY, something like "Alum Silica"..on ingredients. First time ever I did polishing, no mask? Had dry lips for a week!...

For our good Lords sake, PLEASE.."THINK AHEAD BEFORE ANYTHING DOING ANYTHING!

THINK first as the unsuspected, WILL NEVER HAPPEN DOES?

DAMMIT.."gear on first" like going to battle.And for Chris sakes, ALWAYS WERE SAFETY GLASSES! Ya only got 2 eyes, and "protect" them

Never forget one day at work, Wally was straightening out a bent shaft off something, in a massive many ton press. He did dumb move and had the RED painted ..(hardened) V Blocks under. Not the Green!! Well one shattered, and put his eye out for life. He trudged on, (even rode next to him on motorcycles! Just say on the site side!)

Also back in HS, 2 girls, separate instances. Both tossed through the windshield a car wreck. One had MASSIVE facile surgery, one lost site both eyes. At 17 too, and the cutest little blond ever me, the "lost eye site! AND? Think it can't happen? BS!

I was out of Veitnam, in the early 70's now. Had a 1965 Mustang, that me blew a second gear on a WOT power shift. Yanked the case out and second gear was stuck on the shaft. Stupid me took one the OTHER HARDENED GEARS, and gave it a "whack".

WELL? Sliver one tooth chipped off, and stuck in my cheek inch below my left eye.

Again, .."do battle", but go in prepared too! Rather safe than sorry. Wish the best all, just think it it out first!

WHOOPS! My last 2 post should have been the stuck Merc prop, the thread from the Doc. No big, as still Merc forum. Sorry 'bout that!

Thom,
Might be down later this month dropping off my big cat with canvas top guy will let you know. Be good to see what hot little projects you have on the racks.
Did you ever get that book I sent you?

"Did you ever get that book I sent you?"
Yuppp,...And lots of 'new faces' on the rack in the Mercury Magic Shop.
Doc F

Salt kills any outboard. At the minimum, it locks the bolts into the block, making them almost impossible to remove without breaking. I wanted to build a Mk 75 many years ago, but couldn't find one that would clean up enough to be worth it. Water jackets deeply rotted, covers rotted, lower units ruined by corrosive salts. I have a fresh water only '63 650 that is in nice original condition. I refused to sell it to someone that wanted it when I found that they planned to use it in salt water. The narrow passages on inlines traps silt and salts. The cover gaskets also have some areas where the gasket shrouds part of the passages, and even more silt and salt will settle in these spots. The cylinder covers are really prone to being eaten away.

Also, an anode wouldn't have done anything for that engine in Doc's photos. The engine and boat doesn't need to be left in the water for the damage to happen. The silt and salts are lodged in the engine, and this is what accelerates the corrosion.

Dr_Frankenmerc wrote:

One of these days I'm gonna blast the water-jackets in the block and if I can get them clean enough apply a powder coating there too before having any of the cylinders, or gasket surfaces remachined for reassembly.
If anyone has already explored this idea, I would love input.
The Mad Doctor Frankenmerc

Just a thought, if you powdercoat then machine afterwards, isn't the powdercoating going to crack and possibly chip off anyhow?

I too have dealt with the salty dog. What a MESS. Broken bolts galore. There is only so much finesse you can put on a bolt with heat/pressure tactics until it just gives in.

Found this block on the coast of Kaui in 2004. Probably all gone by now.

Its amazing what salt water can do to iron.

I am glad I live in the midwest. Except our cars rust out ever 5 years from road salt in the winter.

C

Hi All. I just came across this thread and quite frankly I'm scared to death that I may have put my brand spankin' newly rebuilt Mark 58 in big time jeopardy. We usually boat out on the Chesapeake Bay and I got my Crosby out about 10 times this past summer. I did however flush it out for about 10 minutes or so back then and then again about a week or so ago for a couple of minutes. The convenience factor says that the Chesapeake is where we will continue to motor around and I was wondering if there is any way to prevent what you guys are describing as a slow death. If I flush it out after each use is that good enough and if so for how long? Thanks in advance for any advice.
shipster

Well we are on corrosion does anyone know if there is a difference between jethot and powder coating? Is it a proprietary blend of powder coat that makes a difference from others, completely different or that same thing?

Completely different. Jet hot was originally developed for the military, mostly the exhaust of the F 16 fighter. It then was used for coating the headers on dragsters. Racers found that if they used it on the inside as well as the outside of the headers it really improved performance. Works great on regular car headers as it keeps the under hood temps down. Powder coating is not for any high heat areas such as headers. It will burn of and the fumes from it must not be breathed in. Kinda can really screw you up big time. There are companys that put out what they call powder coated header but these are not real powder coating. Check out there web site and you will see just what it is. Really cool stuff it you are looking for a high heat long lasting coating for just about anything. Skip.

Over here in the UK most of us have to boat in salt if we want to go above 10mph. My '84 115 has been used in salt for all its life but was always flushed. When I rebuilt it a while back ALL the water jacket bolts came out, not one broke. I use a method many of you will be aware of - give all the bolts a good hard whack on the head (use a drift) a few times the use a 3/8 rattle gun SET TO ITS LOWEST SETTING & gently rattle them out - use plenty oh eat if required. Doesn't always work but does most of the time.

I always flush mine for about 20 mins in a 30 gal drum with a constant fresh water feed into the bottom. After 20 mins I turn the hose of so the water heats up a bit - I reckoned that would shift any residual salt. If I am leaving it I will add anti freeze to the water or soluble oil (as used in a machine shop).

Works for me.

Picture shows the block after stripping & washing off. Only light corrosion visible.

It would of course be better if it had been a fresh water motor but it isn't bad for a salty beast!

Am currently rebuilding my 1974 Merc 200 20hp, purchased new, and although mostly run in salt or brackish water I always freshwater flushed with earmuffs after every use, and garage stored. Always ran great,(2/3 pulls cold,1 pull hot),untill about year 4 when it would cold start fine,but after a while would idle rough,and a lot of trouble to start hot.I discovered a water leak while flushing with the cowl off,right at the bottom of the lower cylinder spark plug hole.Removed the rear waterjacket to find a lot of aluminum oxide corrosion.Took the waterjacket cover to the shop,and beadblasted only to end up with a piece of swiss cheese,painted exterior looked just like new!Bought new waterjacket and gasket,and applied a thin coat of JBweld to the sparkplug bosses, which also had corrosion and pitting,reassembled,and motor ran great again. Some years later motor became hard to start cold and idled poorly again bringing me to my current tear down.After removing the powerhead I was wire brushing the bottom of the block only to find corrosion had eaten a 1/2" hole through the block!Also discovered that the zinc anode was badly eaten away on the back side,(the outside looked just fine).My take is the aluminum alloy Mercury uses in their castings is more succeptible to oxidation,as I also own a 1962 Evinrude 75hp V4 run in same conditions, and still going strong. My advice if you run your Merc in salt is to check the anode annually by removing,and wire brushing,if questionable,replace,also clean the area where the anode contacts the the aluminum housing,freshwater flush with Saltaway,and hope for the best.