TOPIC: Mercury Super Marathon 78 Twin Blade Brass Prop

Hi Everyone,

I am looking for the correct twin blade brass prop and cone for a 1957 Super Marathon 78 inline six. Any help would be appreciated.

Many thanks,

Kenny Lippold
414-405-2957

we w0ould need to know what pitch.or size boat.

As Dave said we would need to know what pitch you need . I have a number of those props here. Let me know what pitch you neeed & I'll see if I have one.

Hi There,

Thank you for your reply. My boat is a 1961 Span America "Pirate." It's 14' and may weigh 400 pounds and I may be lying to you at that. The thing is really light. I will be able to "notch" the motor up to the #2 or #3 pin setting for maximum performance. I also would need the pointed cap that goes behind the prop as well. So what do you think would be the best pitch and diameter for what I have?

Many thanks,

Kenny Lippold
414-405-2957

Hi There,

Thank you for your reply. My boat is a 1961 Span America "Pirate." It's 14' and may weigh 400 pounds and I may be lying to you at that. The thing is really light. I will be able to "notch" the motor up to the #2 or #3 pin setting for maximum performance. I also would need the pointed cap that goes behind the prop as well. So what do you think would be the best pitch and diameter for what I have?

Many thanks,

Kenny Lippold
414-405-2957

I would guess about a 19in pitch, about 45MPH.

I have a quicksilver 46 28267A1-19 left hand pitch for a DR Merc. I also have a '59 Mark 78AE cranks good, I have no title so I can't use it here is missouri. Parts motor, I guess. If you can use these, or anyone else here?

Hi There,

Thank you so much for your response. The 19 pitch is right, but I need a right hand prop (one that goes clockwise for clarification. As far as the parts motor you have, I will keep you seriously in mind as virtually all of the '59 Mark 78's hardware fits the '57. Good stuff.

Many thanks,

Kenny Lippold
Milwaukee, WI
414-405-2957
This email address is being protected from spambots. You need JavaScript enabled to view it.

Hi There,

Thanks for the reply. I would think you are in the ballpark in regard to pitch and speed. I was thinking 19-21 pitch that would give me between 45-52 MPH. As mentioned, the boat is really light. The way the thing is going to be set up is for acceleration and smooth cruising. When finished, it will be a real kick in the pants to drive. Gotta love the retro stuff. Do you have a 19-21P twin brass prop? If so, what would you need to get it off your hands?

Many thanks,

Kenny Lippold
414-405-2957

Also keep in mind I got the motor for free, so I'd probally give it to someone who will really use it for the same price. Daniel

Hi Kenny,

I have a 1959 G3 that is 13' 7" long and weighs just north of 400 lbs. I am running a '63 850 Merc six. I have a Merc 1000 carb set and tuned exhaust plate installed (a '63 850 is a detuned 1000) I probably am running a little over 90 hp. I tested a lot of props last season, and my best setup was a 19P quicksilver stainless steel three blade prop with a slight cup. At 6200+ RPM (too high) riding solo, I am now getting 55 mph. I did a lot of work on my engine vertical mounting height and use a fair bit of trim to see that speed. With my engine mounted at normal height and moderate trim I was seeing 49 mph with that prop. I tried a ton of props, including the older Kiekhaufer two blade 19P bronze props, where my best speed was about 45. I didnt like it as it would break loose easily on corners and while trimming... it didnt have any cup though.

I think your motor has 2:1 lower gears, so it would be my guess that you dont want more than 19P. I just couldnt get the RPM I wanted with a 21P, and it lugged out of the hole.

I would say that Dave hit it right on the head! (45 @ 19P)

Thanks again for taking the time to talk with me yesterday about the prop question. Your information was very helpful

Best regards,

Kenny

Hi Dean,

Thank you SO much for your information! By the way, I LOVE your set-up. Really slick. I will take your advice regarding the engine enhancements and propeller selection. Unfortunately, the guy I was to get the '57 Super Marathon Six 75 sold the thing right out from under me after we had an agreement to buy! Yeah, I was going to drive to Valparaiso, IN from Milwaukee to pick it up today, what a jerk. Anyway, I did find a '61 Merc 800 short shaft that actually will match my Span America perfectly as the boat is a '61 also. So I guess things happen for a reason. Have to drive to Minnesota, but no biggie. I am going to try to replicate what you did with your engine set up. You are right in regard to the 45 MPH with a twin bladed brass 19. I want to be in your range of 55 or so. Is this a fun hobby or what Dean! Meeting so many nice people like yourself willing to help others. Gives me hope for this country!

Many thanks, and a blessed holiday season to you and your family.

Kenny Lippold
414-405-2957

I used to play w/ mark 78s alot when I was younger and found on a boat that size a 17 usually worked best.