Need some help repairing cooling on Merc 500

I just bought a presumably 76-77 Mercury 500 in parts and need some advice.

It ran god and strong until last summer untill the tell-tale stopped squirting water. The previous owner took it to a shop that put in a new impeller but that wasn't enough.
Turns out that somebody has repaired it with a piece of plumbers copper pipe and clear silicone caulk

At that point the shop said it would cost to much for them to lift the power head and fix it, but that he could do it himself over the winter and sourced him a used coolant pipe to put in.

Apparently this wasn't the only do-it-yourself project he had on the farm, there was a seized tractor, a small saw mill that didn't work, a chainsaw without spark and various other things.
SWMBO declared that non essential repairs was done on his own peril and he decided to unload the outboard.

Compression was 110/110/120/???, I couldn't get a good seal with the comp meter on no 4 cylinder so I took a chance it was good to

So what I got for a modest sum was:
- A late 70's short rig Mercury 500 Thunderbolt with lower unit detached and unreadable S/N
- New spark plugs
- A lower unit for same with new impeller and a prop in god nick
- Control unit with cables
- A 6 gallon tank with those
- The old copper pipe
- A pre-loved coolant pipe with rubber seal
- Some plastic bags with zink anode and nuts and bolts, all nuts and washers held together with cable ties
- The name and phone number of the outboard tech who did the original job.

It should be everything I need to fix it.

I flipped the OB up side down and had a peek down the rig .
Next to the exhaust pipe I could see a hole where I presume the coolant pipe should attach to the power head.
At this point I thought that all I had to do was insert the pipe into the hole and reattach the lower unit and that would be it.
However the hole is larger than the pipe and I can drop the pipe a good bit into it.
There seems to be something missing.

The next problem is probably easier too sort out.
The bracket had some severely rusty parts.
I presume that I could get spares from the internet and that a torch, angle grinder and judicious use of gratuitous violence will get the old parts off.

Night has fallen and the hornets have come out, my family and theirs have been neighbours for generations and they know me well, but they are at least 3" long and command respect so I'll leave the porch to them and retire.

We're talking about the water inlet tube.
#40 on this fiche http://www.marineengine.com/parts/m...thru-7143687-can/drive-shaft-housing-assembly

On what fiche is the receiving part on the cylinder block?
The OB is made in Canada if that's important

79799 ---NLA ----Listed on exhaust plate and housing.

Seriously, you need to look for a donor tower for that motor. Lots of them out there with bad power heads.

Jeff

racerone said:

79799 ---NLA ----Listed on exhaust plate and housing.

Click to expand...

#7 on this fiche then, thanks!

http://www.marineengine.com/parts/m...can/exhaust-extension-plate-and-shift-linkage

There's a similar piece in one of the plastic bags that I thought contained replaced parts

fastjeff said:

Seriously, you need to look for a donor tower for that motor. Lots of them out there with bad power heads.

Jeff

Click to expand...

If I can find one, sure, but they are rather rare over here

Item # 7 it is.----But the similar one it the picture is not it.-----That part has to do with the shift rod where lower unit bolts on.

Ok, they are the replaced parts then.
How do I get access to install the missing parts?

I've searched for a service manual but haven't found one.
Nor a user manual. What WOT should I aim for once I get it running?

Hmmm...
Seems like there's possibly two different solutions.

One for the parts you suggested, 3,4,7,8,9 for the following S/N's
UNITED STATES 5193259 AND UP
AUSTRALIA 8057395 AND UP
BELGIUM 9217256 AND UP

No mention of Canada for this part

Part 5,6 for
UNITED STATES 5193258 AND BELOW
AUSTRALIA 8057394 AND BELOW
BELGIUM 9217255 AND BELOW
CANADA 7116222 AND BELOW

My OB proudly states Made in Canada, so maybe the latter is what I should get?
Since 1978 starts off at S/N 4962056, probably

I think this OB might have been stolen at some point in it's history, this looks like a determined effort to obliviate the serial number.
Is there any other way to identify the outboard? Anything else changed at this point in production?

Number 2 in the list http://www.marineengine.com/manuals/seloc/mercury.html .
The plastic bit in your pic is the shift rod and reverse lock guide,fits up into the mid-section.To fit a replacement water tube,you'll need to pull the powerhead,so then you are into an exhaust gasket.
The big rubber seal is the exhaust seal,fits into the lower unit,the other rubber bits are spares out of a water pump repair kit,though the heavier rubber seal fits down the driveshaft on top of the water pump housing.

There may be a number on the starter bracket,decals look like'76 or '77.
Will not matter where it was manufactured,will all be the same

Language barrier, what's the starter bracket?
Don't remember any stickers with numbers under the cowling

Looking on eBay tells me that part 79799 is for 82-97 models and what I need is 38500.
38500 only attaches with one screw whereas 79799 uses two, could the engine be adapted to use 79799, they must have had a reason to change it?

Spare parts are unavailable here in Sweden and eBay from US quotes shipping higher than the sales price
Anyone knows a chandler in Europe who might have it?

https://m.ebay.com/itm/163157300743
https://m.ebay.com/itm/302623235624

???---Why the confusion ?----According to your cowling you have a 1976 / 77 model .---According to the parts book it uses the 79799 part.----I would simply make one I think.----I likely have about 6 or more of them kicking around on parts motors too.

The confusion is that as far as I can tell it should the 38500 part.
I expect that the only way to find out is to lift the power head and have a look.
From what I can see, the sealing is by compression, by fastening the foot the water inlet tube is squeezed tight on the seals.

So just make up a receptacle of hairy putty or steel epoxy

If you want inexpensive try this......................................https://www.ebay.com/p/K11b-Quicksi...itm=182612370931&_trksid=p2047675.c100623.m-1

Yeah, but shipping is $35.99

And then VAT and customs charges are added...

Sellers pay a fee to E-bay on the selling price I believe.-----But not on shipping charges.----Hence some of the high packaging / shipping quotes.

Possibly, but the same thing happens with items that have free shipping in the US.
I think it's eBay's global shipping program, the sellers have no control over their prices and don't get any of it.

And if I wanted two, guess what the shipping would have been.

Just take the powerhead off and see what you need then !

Try these guys,the part will be aftermarket. https://marineparts.ie/

Lifted the powerhead yesterday, and the discussion about what parts to get is moot, I've got a worse problem.





Clearly the best way to fix this was with generous amount of clear silicone bathroom sealant

The proper way to fix it would be to add new material by welding and then drill and shape a new socket.
That's beyone me I'm afraid.

Fix 2 would be to get a new plate assembly, probably not very good chances of finding one.

Any recommendations?


@fastjeff
On a brighter note I managed to find a good bracket, only I forgot to specify I needed the axle as well.

Lots of those exhaust adapter plates available on e-Bay, and not for a fortune. Cheap to ship as well.

On mine, I drill and tap the plate and use tubing fittings to hold the copper tube in place. You might be able to do this as well by cutting part of that broken stuff off and tapping it.

Jeff

A plumbing nipple was one of the things I thought of, I can't get fittings for 1/2" pipe but 12mm ought to be close enough to make it work.

The guy who sold me the clamp probably has an exhaust plate as well, only still mounted on a power head, different outboard but possibly the same part
I'll see what he wants first before breaking out the big files and thread tools

Life took an unexpected turn last summer and the outboard project went into limbo, however I've put it all back together and fixed the exhaust plate with steel epoxy, but I've messed up somewhere.

It starts and runs but it's constantly in forward drive no matter how I turn the controls, I probably made a mistake when I reattached the foot. There was a small square axle I wasn't sure how to attach

I've searched hi and low for a workshop manual but all I can find is one for the three cylinder models and the lower housing is not the same

Anyone got some pointers?

Sure. Put the shifter (above) in forward.

Rotate the foot shifter counter clockwise to take out all the slack. Align that black plastic cam piece so it is NOT pushing up on the companion part in the tower above. (Wish I had a photo--sorry.) Then slip the works back together and go boating (at last!)

Jeff

PS: Thanks for saving another good Merc from the scrap pile.

Thank you Jeff!

I wish I'd known that a week ago.
At least I figured out the black plastic cam thing.

I'll try to get her up on land again tomorrow