Mark 78A

[MOTOboat]

Hello,

I have just purchased a Mark78A I would like to restore, however I'm still trying to run down a set of controls for this engine. If anyone has some connections on where I might get my hands on a set of controls for this engine it would be most appreciated.

Dave

[Mark75H]

Dave, the controls are very particular to this motor. Controls for later Direct Reverse motors do not have the correct internal switches; on the later motors the switches are in the motor instead of the box (these are white instead of green - easy to tell apart). Another thing that makes yours different is that the alternator power goes thru the ignition switch ... problem is that the identical appearing green Mark 75 control is also rigged up the same way but has lighter wire and switch. Back in the late 50's Merc put out a service bulletin about this problem that caused the wiring harness & switch to go bad. I don't know if there is any way to tell the two apart, but the simplest thing would probably be to use an alternator from a 75 or a 4 cylinder to be safe. Mk78 and 78 controls do come up on eBay a few times each year, usually sell for $125 to $250, be ready to pay if you are serious. You can also put up a wanted at on the AOMCI board: http://www.aomci.org/webads.htm

New piston/ring assemblies are available if you need them as are rings for your old pistons if you wanted to go that way. Reloading all 6 pistons into the block at the same time is chore, no reason to disassemble the motor if not needed.

Most parts are long ago not available from the factory, but so many of this model were sold that you should have no trouble finding a back up motor or 2 if you do a little digging. Bob Grubb should have many of the parts you need at www.oldmercs.com. Short shaft boats were more common back then, it should not be much of a problem to find a short shaft motor to donate parts.

[MOTOboat]

Thanks so much for the info... I am pursing the individual whom bought the cottage from the previous owner of the Mark78a.

He told me the controls were at the cottage and he may just give them to me.

Also I want to use this motor. I would have preferred a Mark 78 (I like the shape of the motor top cover better) and the colour (Sunset Orange)

Any suggestions on things to look for to make it as bullet proof? (As a 50 year old motor can be). Can one get any sort of Props other than what’s on it? What kind of RPM can I expect to run it at? Is it rally 75HP or is thier more their since it has 6 cyl. I’m not talking a killer race motor, just optimizing it’s application to geet the most from a stock motor.


I want to learn to maintain the engine myself and have some contacts here in the Toronto area that have experiance tuning the engine and will (for a price) help me maintain the engine.

I would be interested in you opinion using his motor for performance if that is crazy idea... please slap me. What can you say to a guy who runs 2.5 SS on a Stoker eh.. (I solved the porpoise) accelerate harder and trim UP..:)

I have been rebuilding motors and boats since I was 8. I have never however taken on a challenge like the Mark 78A. So I am always looking for input from other experience, I don't want to re invent the wheel. But nothing unique or rewarding is easy...:)

I expect this will cost me more than a newer engine but my dad had a Mark 78 and mark 78A when I was a kid and I always wanted to run one on a play boat... Now got to find a fun boat I can have a passenger that makes the kids on their VooDoos take notice

THX for your insight!
Yeah I’m nuts
Dave

[MOTOboat]

http://cgi.ebay.com/ebaymotors/RARE-MERCURY-DOCKBUSTER-CONTROLS-W-WIRING-HARNESS_W0QQcmdZViewItemQQcategoryZ31283QQihZ016QQ itemZ260160130884QQtcZphoto

Hi Sam,

Would these work for me?

[Mark75H]

No.


That type does not have the micro switches in the control itself, it is for the early 1960's type Dockbuster, just like the seller says in the description.

The early type has the switches in the control box, the one on eBay uses switches on the motor. Different number of pins and positions on the plug, too.

[MOTOboat]

THX just thought I'd ask...

[Roy Hodges]

since nobody else answered , their rated hosspower wuz : 70 !