The "Dockbusters"

Mercury Outboard  general discussion

The "Dockbusters"

Postby mercules » Fri Apr 12, 2019 5:17 pm

Got into a squall on another forum about the dumb idea behind the DR motors and it occurred to me that Sea Doo, and others, made nothing but dockbusters for years - far longer than Mercury (my friend had one in the 90's!) and my brother in-law actually ran into our dock with one bending a support pole!
So who's the dumb ass; Mr. Kiekhaefer or those Bombardiers !
When you get 5 gibronis up from the city going around in circles just off shore, for hours, you really get to hate them.
Let's fix it now - before we launch the boat.
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Re: The "Dockbusters"

Postby ctpdsr » Fri Apr 12, 2019 6:23 pm

Chapter 21 of "Iron Fist" provides some interesting perspectives. The development of the MK75 was a brilliant engineering feat. I have had the honor to meet both Charlie Strang and Edgar Rose and can't imagine the environment they worked in at that time. Two things stood out to me. One was that they knew an FGS was needed and developed one on the side without Carl's knowledge. Also, the company was under financial stress due to the massive Stock Car Racing program. Perhaps part of the rush to market the inline six?


Good news is the PWC "swarms" seem to be diminishing here in WI.  Bad news is Wakeboard inboards throwing up walls of water are ruining shorelines and boat rides!


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Re: The "Dockbusters"

Postby JW in Dixie » Fri Apr 12, 2019 10:21 pm

Had and used a DR for years. Just don't see any problem with them. Cheers
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Re: The "Dockbusters"

Postby ctpdsr » Fri Apr 12, 2019 10:46 pm

I would love to try one on a light hull some day. With the small profile gear housing and big brass two-blade prop, I bet a MK78 DR would beat the pants off a Merc700 FGS. From a marketing standpoint, while I am used to "pull the rope and go" non-shift applications, 95% of the buying public is not...

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Re: The "Dockbusters"

Postby mercules » Fri Apr 12, 2019 11:26 pm

JW in Dixie wrote:Had and used a DR for years. Just don't see any problem with them. Cheers

Amen brother!
Checkmate.jpg

The 700 has Jet Prop exhaust which makes the gearcase longer and slightly wider than a Mark 78.
Let's fix it now - before we launch the boat.
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Re: The "Dockbusters"

Postby dave bernard » Fri Apr 12, 2019 11:52 pm

Back in 1958 I was 12yrs old and ran a 14ft Prywing with a Mark 75 at 47-48 mph. and had no problem with the DR system.
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Re: The "Dockbusters"

Postby Dockbuster » Sat Apr 13, 2019 2:22 am

I have two running dockbusters. One of them can turn a 19 inch prop. Admittedly it needs a bit of leaning forwards to get on plane and only one person in the boat but pretty impressive for a 66 cube that's now 60 years old.  
Too bad they are fast,they won't last.
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Re: The "Dockbusters"

Postby mercaholic » Sat Apr 13, 2019 3:09 pm

JW in Dixie wrote:Had and used a DR for years. Just don't see any problem with them. Cheers


:arrow:
Mississauga , ONT
Canada
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Re: The "Dockbusters"

Postby Deep C » Sat Apr 13, 2019 6:05 pm

Based on the performance achievements of the dock buster motors it is not logically possible to dismiss the motor because of the silent neutral. It would be like saying the Apollo space craft had touchy steering so it was not that good.
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Re: The "Dockbusters"

Postby Tom Brockmeyer » Sat Apr 13, 2019 6:34 pm

Deep C wrote:Based on the performance achievements of the dock buster motors it is not logically possible to dismiss the motor because of the silent neutral.


How about due to it's overly weak charging system?
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Re: The "Dockbusters"

Postby dannynagasaki » Sun Apr 14, 2019 1:13 am

I only learned about these amazing motors from the early years of this site. I'd never seen a Mark 78E growing up, not that they weren't around just not where I was. I immediately knew I had to have one and eventually found one and then a second one for parts. The first one I ever heard was mine and then decided that I wanted it to power my 12' Humber Jewel. I then wanted to have power trim installed to navigate around rock shoals and islands in my area and to save my back and though it wasn't available for this motor, with the help of the knowledgable regulars here I now have power trim. This year will be the first year that I know I will use it a lot as up to now it's been about getting to know this rig and ironing out the bugs. I currently have a 21 pitch two blade bronze prop on it and although it is a bit slow coming out of the hole, I can come out with a passenger and she flies when it's out. It now runs beautifully... :D
55' Mark 25, 55' Mark 55E, 58' Mark 10, 58' Mark 35, 58' Mark 78E (2) 62' Merc 60, 62' Merc 450, 67' Humber Jewel, 74' Grew SS140, Oak Ridges, ON (winter), Wahsoune Island, Georgian Bay, ON (summer) Canada
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Re: The "Dockbusters"

Postby 1500J » Sun Apr 14, 2019 1:19 am

ctpdsr wrote:I would love to try one on a light hull some day. With the small profile gear housing and big brass two-blade prop, I bet a MK78 DR would beat the pants off a Merc700 FGS

Chuck


The one thing a 700 FGS has over the MK 78 is the 15 spline prop shaft.....

That means it can run modern props that will let you run higher and faster.  The MK78 is stuck with the old 12 spline props.

Ive got a 700 DR and it has 15 splines.  I can run Left hand modern props on it if I want to.  LHR Super BP props should be a good option too :)

C
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Re: The "Dockbusters"

Postby Deep C » Sun Apr 14, 2019 1:44 pm

Tom Brockmeyer wrote:
Deep C wrote:Based on the performance achievements of the dock buster motors it is not logically possible to dismiss the motor because of the silent neutral.


How about due to it's overly weak charging system?


I have the charging system removed when I have an old Mercury redone, battery chargers are not that hard to use.
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Re: The "Dockbusters"

Postby dave bernard » Sun Apr 14, 2019 2:57 pm

You need the charge on the DR's because it has a battery ignition like a car.
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Re: The "Dockbusters"

Postby Jeff Register » Sun Apr 14, 2019 3:43 pm

So right Dave & don't forget all the restarts for reverse. Still have my DR & wish I could run it, my health won't let me.  [icon_sick.gif]  
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Re: The "Dockbusters"

Postby 1500J » Sun Apr 14, 2019 3:52 pm

I still have two.  

1957 MK75 I ran this one probably 10 years ago.  Sweet little running motor.

1960 700 DR  This one came with a rusty crank and a hole in the exhaust plate.  I have since gathered the parts to assemble it again.  Just need to do it.

When the points are set correctly these motors are surprisingly easy to operate and take very little to start.  Once warm just the slighted pop of the starter has them running.

Have them out of tune and you will be cranking a lot and killing your battery.

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Re: The "Dockbusters"

Postby EdMc » Mon Apr 15, 2019 1:24 am

Years ago I picked up a 700E out of the Little Nickel wand ads.  $25 with controls!  Cleaned out the water pump, cleaned/set points and she purred like a kitten.  It ran really well on a 13-1/2' Sea King runabout.  

It would deep-water start me on one ski, and made my good boating buddy's head swim when we took off extra hard for a "beach start".  Some guys at the ramp were laughing at the old boat and ugly old motor, but they weren't laughing after we took off!

It ran so sweet, started and idled like a dream too.  Would push that old Sea King 35 mph.  A heck of a Bargain Basement rig, we got a lot of use out of it.  

So, yeah, what Conrad said, get the ign and carbs set up right and they'll start instantly at a push of the button!

With less frictional loss in the gearbox (one less gear rotating in oil = a lot less drag), they put good power to the water.  The little 66-cube engine was really easy on fuel, too.
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Re: The "Dockbusters"

Postby JW in Dixie » Mon Apr 15, 2019 3:25 am

Jeff Register wrote:So right Dave & don't forget all the restarts for reverse. Still have my DR & wish I could run it, my health won't let me.  [icon_sick.gif]  


Is that the 700 Jeff?  Cheers - I had to give up the Eagle boat. :(
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Re: The "Dockbusters"

Postby Peter » Tue Apr 16, 2019 3:15 am

My arctic cat snowmobile is a direct reversing motor. The technology is still going strong.
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Re: The "Dockbusters"

Postby Tom Brockmeyer » Tue Apr 16, 2019 12:45 pm

Peter wrote:My arctic cat snowmobile is a direct reversing motor. The technology is still going strong.


...as were all the old two stroke Harley-Davidson three & four wheeled golf carts.  I had a 1973 Harley three wheeler and was able to completely rebuild the engine with in-stock parts shipped from an aftermarket dealer (new 0.020" over piston, new crank & rod, new bearings, seals, carb and ignition parts).  It was 14hp and would haul three adults up any hill we could find.
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