TOPIC: 59 mark 78a parts

I just got a really nice 59 78ael the other day.110-115 psi all cylinders. Older repainted. Everything is in great shape. It does need a forward starter solenoid and the impeller pump. From what I've read there are 2 rubber "duck bill" pieces in the water pump. Is there a source for these old parts. Or does anyone have the proper name for them. I've also heard from an old man and read something online about modifying the key way on sierra# 18-3052 impeller and it fits the old dock busters. Does anyone have info on this? Could mean cheap replacements that are still made. 14$ vs 50-60$

Hopefully I'll have it up and running soon. Then it's getting put on a 61 alumacraft queen merrie 18' runabout.

Nice score you've got there!

I am in the process of building up a mark 75 and have had good luck with Oldmercs.com for parts.

I think (you may want to double check) that he probably has your impeller in stock but it is probably not cheap. As far as the duckbills are concerned, you should be okay running the originals as long as they are not ripped or hard.

Good luck with the old girl. There are a ton of guys on here that are much more knowledgeable about them than me that should be able to help out.

Scott

Welcome dude! Robby from S+F!

www.vintageoutboard.com

What does everyone use for starter solenoid on these. Original had been discontinued a long time.

What does everyone use for starter solenoid on these. Original had been discontinued a long time.

craveman85,

WELCOME ABOARD.

Unless he's sold it in the last few days, I know where there is a MK 78A "parts motor". - What do you NEED, presuming that he still has it????

yours, satx

Pretty much just the starter solenoid. I'm sure a newer one could be rigged in it's place though.

here's a water pump impeller if your looking for one...

they take 2 starter solenoids

I know. My forward one isn't working.

I have one if you need. 1 914 310 7086.

Option 2 grind the rivets off. then resurface the contacts and use bolts in place of the rivets.

One thing I was wondering is if anyone has modified a readily availability solenoid for it. I'm not looking to just Jerry rig something together. I'm looking for a long term replacement for discontinued parts. If it's hard to find something now I'd hate to try in another 30 years.

The ebay item id given is invalid, no result has been sentI think yours takes the "32445" solenoid which was used on other motors as well. Although it's now NLA from Mercury. Found a few in an eBay search:




I've also attached a pic, take a look and if that's the same bracket as your solenoid, it should fit. Most of these old solenoids are the same except for the bracket.

BTW here's a parts diagram for that, hard to read but better than no diagram at all!

www.mercruiserparts.com/Show_Pictures3.asp?dnbr=32912&ivar=images/MARK/32912/E8.png&inbr=1720&bnbr=80&bdesc=STARTER+MOTOR%2C+STARTER+SOLENOID%2C+RECTIFIER+AND+WIRING+HARNES

HTH......ed

craveman85,
The solenoids you'll need are different inside than many of the other Merc solenoids that look the same.
Your solenoids have 12vdc+ going between one of the small terminals & the front coil to supply a full 12vdc to the ignition during starting.
Most other Merc solenoids that look the same have a wire going to engine ground rather than having 12vdc+ during starting.
This is an internal difference between your style solenoid & the others.
The other small terminal on both style solenoids has the yellow wire to engage the solenoid.
I have quite a few used DR solenoids and would bench test them before mailing if you decide you would like one, or two.
If you are interested, and Dave Bernard doesn't have what you need, just send me a PM (private message) and I'll hook you up.
doc

Doc is right about that! Attaching a wiring diagram which shows the connections from solenoid to coil.

Darn I was hoping for a long term replacement. I just ordered a dockbuster starter with both solenoids from johns old mercury parts for $54 shipped.

Was there a model specific repair manual or just that pre 65 mercury one?

Oh also are these a generic mercury tank fitting or some ancient oddball thing.

craveman85 wrote:

Oh also are these a generic mercury tank fitting or some ancient oddball thing.

Takes the standard Merc connector used for many years.

www.iboats.com/Tempo-220035-replacement-parts/dm/view_id.467584

What fuel mix did they use back then? What did they use in the lower unit? Any specific 2 stroke oil I should use?

Late getting in here.
I do have a 78a parts motor. Its a shorty.
1 208 507 0519
Glad to help if I can.


Neil

A local marine shop had 6 impellers in stock. He couldn't figure out what to charge me so he gave them all to me for $100. 5 off them will stay packed in dielectric grease and I'll take the one in the motor out and pack it in grease every year. These 6 should last me quite a while.

The check valves were in good shape so I also put them in the grease to soften up a bit more.

Back in the day the recommended mix ratio was 25:1, but oils have improved since then and the Mark 78A and other old Mercs are properly lubed at 50:1.
Always make sure that the 2 stroke oil you select has the additive TCW3 on the label. There are different additives for different 2 stroke applications, and TCW3 is a must for the 2 stroke outboard.
I prefer AMSoil full synthetic. It has minimal if any visible exhaust smoke.
I always add Sea Foam to the mix to keep carbon deposits soft and moving rather than building up and causing rings to get stuck, etc.
There are other brands of carbon softeners, Quicksilver, OMC engine tuner, but I don't have much recent info on those products.
CRC makes an excellent aerosol engine fogging spray that also softens carbon very well.
Never use ethanol gasoline.
Today's 90wt Quicksilver High Performance gear oil is what I use in both old & new Mercs. Quicksilver also has a 90wt gear oil that is for smaller outboards - like the 7.5, 110, 20hp, etc that aren't being run hard most of the time.
I would have to research what was originally used in the 78A, etc, but the smaller Mercs of the same era originally used "Lubraplate 105", but once again, the gear oil has improved so much that today's 90wt is best IMHO.
If you find water in your gear oil, and don't plan to re-seal the unit immediately, Lubraplate 105 will help suspend the water in the lube until you repair the situation.
Obviously, and immediate repair is recommended, but that isn't always possible, and you might be wanting to see just how well the 78A performs before spending more time & money.
Properly synchronized, the 78A is quick to start and runs as smooth as a sewing machine.
doc

Um... where's the thermostat? Waiting on my manual. My duckbills softened up nicely with silicone. When I get done cutting gaskets and flushing the system I should be all ready to start testing.

No thermostat on a mark78.

How much oil does the lower unit take? Is there only the drain screw on it? Looked like thick grease in the lu

grease was correct back then. there is a Small screw for the vent just under the cav,plate.

How the hell do you pack grease in there? Looked like white lithium grease.

squeeze it in the bottom hole and it will come out the top when full. lubriplate 105 OR John deer corn head grease.

I'm waiting on my gear lube to come in so I can put the lower unit back on. I did mint it to my boat and shoved a garden hose over the water pickup in the mid section. I hooked it up to a tank of fresh ethanol free gas, seafoam, and 25:1 amsoil synthetic. It fired right up when I hit the button. I let it idle for about 5 minutes. Never had a hiccup or burp or anything. I do need to extend my wires and her a new cable though. Anyone know what kind of cable I should use? Or are mercury ones pretty much generic.

If they have rack in the box which I think the do. use Teleflex OMC pre72 naked cables and use all the metal ends from your old cables.

Rack? Have a picture of what you're referring to?

if in the box the end is a flat gear on the end of the cable . call me 1 914 310 7086

Any suggestions on getting the impeller in place? I like the omc ones where you put it I the keyed shaft and rotate the shaft while pushing the housing over it.

To install the impeller on the 78A, grease the driveshaft down where the impeller will be when done, and grease the key (similar to a needle bearing), and draw a line going vertical directly above the key, so that when you get the impeller close, you can align its keyway with the key.
Mark the top of the impeller with a dot showing where the keyway is in the impeller.
Put the impeller onto the driveshaft.
Slide it down to an easy level to control it while you wrap a zip-tie around it, and tighten the zip-tie. Make sure to keep all (6) impeller blades bending the correct direction as you tighten the zip-tie until it holds the (6) blades bent over significantly.
Cut off the extra zip-tie end.
Since the stainless 'cup' that the impeller will go down into is off-center - locate the widest area between the driveshaft and the edge of the cup, and rotate the driveshaft so that the end of your zip-tie will be above the widest area of the cup when your impeller aligns with the key.
Then grease the cup & impeller blades, and carefully push the impeller down onto the key.
Once down on the key, and while still holding down on the impeller, turn the driveshaft and see if the key stayed in place and is rotating the impeller.
If all is good, and while still holding down on the impeller (so it won't try to slide back up the driveshaft), fish out the zip-tie enough to safely cut it, and then remove it.

doc

Got the water pump back together. Now if I could only get this damn lower unit back on. On a side note the seller finally shipped my manual after over 2 weeks. Hopefully it will be here this week.

Hey, piece of cake, there's no shift shaft!!!

Make sure the water tubes have a bit of grease on the outside & the driveshaft splines are greased-up; the water tubes should line up first as you "stab" the lower unit in.

Next will come the driveshaft to the crank splines, and you'll need to turn the prop as you're pushing the lower unit up, so the driveshaft will align with the crankshaft (I'd recommend turning the prop in the "Fwd" direction).

It should go right in, Easy Peasy! Be sure to keep the lower unit straight as you're installing. You may have to kinda "feel" around to figure out where the hole in the bottom bearing cap sits.

If all else fails, turn the motor upside down and do it that way. Works great on the small ones, a bit inconvenient on the large one if it's still bolted to the boat!

HTH & G'luck.........ed