Does anyone know what

[Damage Inc]

motor this is? Is it worth anything? Can it be restored?

Thanks!

[Damage Inc]

Here's a pic of the manual.

[Damage Inc]

Thanks for the help!

[ken medendorp]

Did those motors run backwards for reverse?And is that the way they got the nick name dock knocker? Because you would have to shut them off and do something (idon't know what)thenstart them back up in reverse and by the time they started the boat would hit the dock.Just a story I heard.Is there any truth to it?

[agreynolds]

These motors definately run backwards. They have two coils, two starters, etc. I have one restored on a 63 norris craft and it will fly. The point gap is critical to get these motors to run correctly. It's .008". Good luck

[largecar91]

Yeah, you can bolt a speedie up to them and still have reverse!:D

[Mark75H]

Speedmasters do not fit the Mk75/78/1960 60hp lower unit bolt pattern, it is a little off. The powerhead will fit on mids that fit Speedmasters ('61 and later). Second consideration with Speedmasters is that most use the later crank spline/drive shaft spline and the Mk75/78 uses the small spline. You'd need a '61 70hp Speedmaster or find and transplant a 700 FGS crank into your older motor to use a 80hp, 100hp or later Speedmaster. The third consideration is that props for Speedmasters start at 15" and go up. If your boat isn't 75+ mph capable, you might lug the motor and burn it up just trying to get on plane.

I have about 10 of these motors

Looks like you have one of the most important parts ... the control box & wiring harness. The control box and harness are special to the DR motors and there are at least 2 different types that are not interchangable. Keep the controls with the motor.

Not only is the point gap critical, the sync between the points is critical. 3 cylinders lagging behind the other 3 drops power 30% even while all 6 seem to be running normally. There is actually only one starter that runs both directions

The year of that motor is 1957 or 1958. 1959's say Mark75A.

[Raceman]

One other tidbid............ they don't have 2 starters. What they do have is a double Bendix that kicks upward or downward on the flywheel gear depending on which way the starter is engaged.

Incidentally for all you guys that have multiples, I'd like to have a decent (not necessarily running, but complete and not stuck) Mark 75 to hang on a stand. I've got a Mark 78 and Mark 78A, but never have run across a decent 75 around here. I'm lookin' for shortshaft only.

[SportJ-US-1]

These motors definately run backwards. They have two coils, two starters, etc. I have one restored on a 63 norris craft and it will fly. The point gap is critical to get these motors to run correctly. It's .008". Good luck


Two coils, one for each set of points and each runs 3 cylinders. The point gap is important on the primary set of points for reference, the second set is set so that it is 60 degrees after the first point set. A single starter, with a double bendix, but it can turns backwards for reverse via dual solenoids. The throttle was pulled back past the center position and backed the dist around for the correct reverse timing. If the dist. is set up right and the carbs are correctly synced, then these engines start in reverse very easy. The "Dock Buster" term is because most people don't bother to keep their engines properly tuned. I ran a Mark 78A (66cid version) for 3 years on a Sande Ace (12 foot Mahogany plywood go fast from the same era) and never once dinged my boat or a dock, mainly because I checked and readjusted my dist. every 6 months.

[Damage Inc]

Here is the serial number: 1076489

From looking at oldmercs.com, it appears to be a 1957 Mark75E. Anyone else agree?

[Mark75H]

107xxxx sounds like a 1957 serial number; the only choices were Mk75E or Mk75EL there were no Mk78's in '57

[Dave S]

Free cubes:D