TOPIC: 50hp Rebuild?

Hi, i am hoping to get some advice/opinions. I have 1971 50hp powerhead that was partially submerged in salt water for a few days. I did start it a few days after it was retrieved, it started but it didn't sound to good, at that point i poured oil in the cylinders and it has sat for the past three months.So today i split the powerhead to try to determine whether it is worth rebuilding. Looking at it i'm thinking with a good cleaning and new top and lower bearings and needle bearings it might be ok. I have never attempted to do a rebuild so any advice would be appreciated.
thanks

more pics

one more

take the rods off and check the crank. also take the pistons off and check the pin bearings. better safe than sorry.

I agree with Dave B, there is an awful lot of rust there. I suspect the needles will have etched the bearing surfaces. To be honest I would not hold much hope for a good crank there.

thanks guys, i will probably get back to it in the morning and post more pictures, we're getting snowed in here so it will give me something to do.

Both Dave's advice? YES YES AND YES! Seen many the Doc's motors torn down and YES! Yank the rods, and check the crank, as the rest ANY needle bearings. Salt is NOT nice to old Mercs one damn bit.

hi, Thanks robby i was planning on taking it apart as needed. it does look like the crank is etched, so should i give up on this one,would some parts still be usable?, i do have another powerhead that might have a good crank.
thanks

I would try to rebuild the other power head.

dave bernard wrote:

I would try to rebuild the other power head.

Again, I am with DaveB on this one.

Daveswaves wrote:

dave bernard wrote:

I would try to rebuild the other power head.

Again, I am with DaveB on this one.

Yup, the crankshaft in the pic has had it!!

OK i guess it's unanimous, i really didn't have to many expectations for it but i had some time to kill while waiting for the blizzard to pass. thanks again

Yup..that crank is now "shop art"...to bad!

But NOTHING is junk to me. I was a Machinist 21 years at Reynolds Aluminum. Many times I've done same worn out/etched crank journals. Simple stuffed a lathe, cut down to good metal, then the "Red and Green" hand torch out and "spray the Metalized powder" on for a good rebuild journal. Simple me is nothing is "junk", that can't be "fixed" But maybe a good "crank shop" to do right? Probably cost prohibitive..but I got a REAL "soft spot" life heart me "Mercs".

Great job checking the crank as told. That middle crank rod journal is toast! But fixable too! Link...

republicdiesel.com/engine-machining/for-sale/crankshafts/

Unfortunately the bearing surfaces are hardened to Rockwell 60 or better. Not like an automotive crankshaft where you can machine 'er down and install new bearings to fit.

There are shops that repair outboard/motorcycle/etc crankshafts that have needle or roller bearings surfaces. The process is a bit involved and the crankshaft must go thru a heat-hardening process then straightened-out.

Such as this one: www.marinecrankshaftinc.com/outboard.html

Those companies have supposedly perfected the art of repair, but it is expensive. Cheaper than a new crankshaft of course, but there are only so many bad journals they can repair on a crankshaft, due to cost and physical reasons.

IMHO I would still prefer a good, used crankshaft with the original factory journals. There are enough 50hp parts around that it wouldn't make sense to rebuild a 50hp crank.

Now, if it were a rare Twister crankshaft, that might be altogether another subject! Those don't grow on trees, that's fer sure!!

Never have seen a crankshaft tree, that'd be handy though!

Cheers......ed

Good point there Ed. Yep, any journal ever did us was a plain bearing so needle bearing cranks are different..(hardness). Ya on the ball as usual!

ok here is candidate #2, it looks better, everything moves more smoothly, the #1 and 4 pistons had one stuck ring. Before i go any further is there anything i should check? Also do i need a special tool to reinstall the pistons on the connecting rods?

Number 4 piston is toast, number 3 looks like the skirt is damaged but it could just be the angle of the photo. See if you can make 4 good pistons out of the 8 you now have. 3 from the original looked pretty good.
To re assemble the pistons on the rods does require a "tool" but you can make one easily.

Shame about that engine that took a dunking, but let it be a lesson to the rest of us. You get it wet then get it apart pronto, or suffer the same fate.

If you cant get to it right away, just submerge it till you do. don't wait to long but keep it under water.

Yes. ESPECIALLY if it went down in salt, get it into a barrel of fresh water until you can get it apart, but sooner rather than later. No more than a day or so.

FYI, it's already apart, the damage is done. Don't take long to rust away, sitting in salt water!

Definitely would have been better to tear it down immediately after submersion. Sometimes if you can get them running right away, and then run 'em for at least an hour at speed, getting good 'n toasty, it'll flush the worst of the salt out of the innards.

Point well-taken, though, if you can't get to it right away, a good fresh-water soak will at least wash a lot of salt away and keep air off the metal. The salt really takes a toll on all the wiring & electrical components as well.....ed

done many of them when I worked in CT back I 1970-75.

Use the best pistons from both motors, best set of rods, best block, etc. If you lack anything, I have a ton of 44-cube 50hp Merc parts.