TOPIC: Mark 78E powertrain swap

Everyone knows .... The Mark's cowling is beautimus.

Are all the 78's DR shift?

Guess I'd like the best of both worlds to avoid dock busting, meaning want.... FGS.

Can the Mark style cowling be put on more modern 70hp powertrain?


Excuse the dumb Q, I'm sure this has been covered but I can't find write-up.

I'm thinking that you could use the Mark 78 style lower pan, wrap and rewind housing on a 700FGS custom assembly. NOT POSITIVE mind you - but think it's possible.
The Mark 78 powerhead is basically the same Super Marathon 66ci as the 700FGS, but you would need to use the crankshaft and distributor out of the 700FGS in your assembly and most easily done if you used the entire 700FGS powerhead and just used the 78 pan, wrap & hat.
Throttle linkage and shift linkage are my primary concerns, but I think you could do it.
If Marathon6 spots this post I'm sure he can answer this question accurately.
Thom

Thanks Thom... I've read alot of your posts. Also love your handle.
My wife gave me mine as I spend more time with my Red Jeeps than her. She tolerates my Jeep hobby as she knows my mind is not on chasing other women.
About me.... I'm an experienced bass tournament boater, had a Gambler with Merc 200 & wrecked my buddies Gambler with Merc 250 pro max. Hit a cypress tree on river ...sideways after boat hooked and spun (I need to scan & post picture, looks like Jaws took bite out of side all way to middle of boat)
Retired from 80 mph speeds and now just live & fish at our club lake & have a 15' Raycraft with real low sides (it scoots along pretty fast) and Merc 70hp with jackplate.

Anyway newbie to the Glassic ski boat and vintage classic Mercs.
Think (well definately) I'm already an glass addict.


Frankenmerc Engine:

Making the linkage arms come out in same holes as MK cowling would probably have to be custom made. The MK lower pan, cowling and faceplate are so dang georgeous that I think it would be worthy project motor.

I also wonder about tilt & trim on the MK's ?

I also like the looks of the 62 Cloud White 700FGS.


I've been searching and studying up on the Mark 75 & 78
Just don't think I could turn my kids loose with a DR engine.
Hope doing a Frankenmerc isn't sacriligious, I have collector Jeeps and go to alot of trouble with PTO winch and rear farm PTO driven implements...so I understand what makes mechanical stuff special & a counter rotating engine & dizzy is pretty dang cool...especially in late 50's.

Living at lake in warm East TX we use boat probably 3 times week, so while I turn alot of wrenches on Jeeps...I'd like to build a reliable motor.
Heck I wouldn't mind a Fitch FI Merc with the MK cowling.

The private lake which we live is restricted to 70hp 2 stroke and 90hp four stroke, so I need engine to be all it can be to pull kids on salom ski.
My Merc 200 got low on compression, so sent block to IL to have balanced forged pistons and raised compression.
Will do same for this small ski boat engine.
The boat dealer in town used to have lots of 50hp cowlings before lake club raised hp limit to 70/90. Sneaky Pete with nitrous.

Boat:

Been looking at Glasspar G3's and sorta like the Glastron GT150.

Thinking about pulling trigger on the Red/White 71 on eBay right now....it's a long ways off and I don't have time to see in person. Also has red band Merc 80 (guess I could change decals to 70). Seller just bought it few months ago so gotta wonder about that.

Was there a sexy looking bowrider ever built?
I can't find one that looks good.
Do hydro boats pull skiers and tubes?

The lake has fairly sharp turn at the dam, so need boat to corner good.

Since they made a 700DR and a FGS in 1960, the lower pans are the same. I think you may be able to change just the hat to the Mark series, then you can hang the faceplate and use the full stainless wrap. Of course a paint job will be in order. I will ask you though, which year 78 face plate did you want to use? The later 78 hats were just like the 700 style. Did you want to use the earlier "rounded" style??

Jim, that's an awesome hybrid Merc on your youtube video.
Is that a Skagit boat? Looks like it's really cooking along nicely.

I read where U posted this:
"the larger spline drive shaft started with the 700 FGS & the '60-'61 800 DR, serial numbers 1335465 - 1379805 "
So guess I want the larger spline drive shaft Merc 700.

I like both faceplates and would probably restore very nice of each to "change hair look" on my Merc.

I plan on going full tilt with this Merc restoration. Hoping to get more than 70 hp from build.

Any hop up info or threads on boring & stroking /raising compression / lightening rotating assembly and still have reliable engine?

What should I lite it with? Swap to modern ignition system?

With ya'll experts help....so far having a beautiful kid friendly 70hp motor is easier than I thought.

Sorta found a bowrider that I like the 68 Glasstron GT. Driver and 1 passenger sit at rear of boat windshield all way to rear of boat. Pretty unique.

Attached is picture of my largest bass 15 years ago in my Dad's 1972 unknown stick steer, (it had a Merc 50 T/T) I spent many hours on water for that LM Bass.
URL=http://i226.photobucket.com/albums/dd178/RedScrambler/photo-140.jpg] [/URL]

Red M,
Attached is a picture of my G3 with a true Frankenmerc on it.
The Merc has a 1961 800FGS top hat and cowl wrap.
The powerhead is a 76ci inline-6 850FGS with mid'70s solid state ignition installed.
The lower pan is 1961 800FGS, and the same pan that was used for the 800FGS, 850FGS, and the early 90ci TIGER blocks like the 850 TIGER through the 1100 TIGER. (the 1100 is a TIGER block like the 90ci TIGERs, but is a 93ci due to larger sleeves.
The mid-housing - or - drive shaft housing is a shorty (for 15" transoms) and is the same housing used on the 700FGS thru the early TIGERs that didn't have a separate exhaust extension plete under the powerhead.
The power trim is off a mid'70s inline-6 - like an 1150 through 1500, etc. Many 4 cyl Mercs also used this trim system.
The lower unit is off a 1963 1000.
So,...I am safe in saying,...It is a true Frankenmerc!!
Unless your local fish cops or neighborhood lake watch are Merc experts - - - a 100hp is just a couple inches taller and a decal away from appearing to be a 70 hp.

Thom

Thom,

That took bunch of spare parts to make that engine.
So let me get this right, U have 85hp with solid state ignition?
But could go Tiger 1100 ?
Would a Mark 75 front face cowling fit on 800 ? 800 looks engraved on face?

There is one jealous inbred guy we nicknamed "water smokey" that used to be all mad that there were 65's with 50hp cowlings. He went around to boathouses and wrote down everyones serial numbers and ran #'s.
He came to annual meeting and threw a big fit, so we fixed him and changed bylaws to 70hp 2 stroke and 90 four stroke engines.
Nothing in rules that restrict modifying motors.

We did make another rule that it's members boats only, so have to have boat & motor registered in member name. Our lawyer actually advised this and member has to have liability insurance on boat.

So what part of motor do U get registered? The tilt/trim unit?

Are the QUINCEY LOOPERS 700 blocks hard to find?

I also want this motor to be real loud and scream, old school tower's are cool.... how do U modify exhaust to be loud?


Here's pic of my buddies Gambler that I wrecked. Tree went all way to keel of boat. My brother and his GF got fiberglassed but everyone was OK. Accident happened from guy coming up river in john boat and guess saw me hauling azz and (thought I couldn't make slide) and decided to cut in front of me & got to inside lane of river bend. I bumped left to avoid him, but engine was too high to bump right and boat hooked. Had I been more experienced with the foot controlled hydraulic jackplate, maybe I could of saved.

My Chocolate lab (in background) was a pup then and he just passed.
Buddy had borrowed my Red Gambler 18' as he was guiding at Lake Fork and his boat was in shop.
He punched a hole on stob in my boat....so payback. (kidding)
He actually came out real good on claim, he was fishing BASS and sponsored by Gambler, so he got boat at cost & insurance paid him for full retail since boat only month old + he got Detwailer Jackplate & Merc 250hp for salvage.





Another pic of my 90 Merc on 16' pulling family... this July 4th.
Background is redneck yaght club on shallow island.
IMG] i226.photobucket.com/albums/dd178/RedScrambler/photo-196.jpg [/IMG]

Will the face plate of Mark 75 or 78 fit on cowling of Merc 800FGS ?

no. the top cowl set up different.

What about Mark 75 / 78 top hat, Merc 800FGS wrap ....

Then would Mark face fit ?



I would think the 800 block is taller than 700?

So close to 100+ hp with Mark style... I can hear it.

yes,

So I have looked into this swap in detail. The easiest stealth swap there is. Get an FGS 700 and swap out the upper cowl. Depending on year of the 700, on the lower cowl you might have to swap out the curved piece that the faceplate knob will atttach to. Some 700's had a threaded knob like the 78/75's so those are all set. The later ones had the half twist knob and need this piece on the cowl swapped to a threaded one OR use a half twist knob on your 75/78 faceplate.
The lower pan on the 700 has the SS trim so remove and polish to match the upper cowl or add a SS band to the upper 75/78 cowl.
For icing on the cake swap on a 75 or 78 wrap as these were unpainted polished SS. I have all the parts to do this and am considering the 700FGS with 58 Mark 78 cowls to use on a 58 Lake and Sea I have to restore. I like the quirkiness of the DR but it is a hassle.
Another alternative which is even more stealth is to swap on the top half of a 75/78 powerhead and top cowl/wrap/faceplate onto a Mark 55 lower/mid. I belive if you are not an idiot abusing it the FGS of the Mark 55 or later 400's etc. will do fine with the smaller 6, this will look more correct and shift. I'm a little surprised not to see these these swaps more commonplace.
Randy

I forgot to mention the 800/850/1000 (same size) wrap and cowls are all too large to fit the 700/78/75 (same size) The cowls look very similar but are larger. The wraps are also different sizes. The 75/78 faceplates only fit the correct top. The 700/800/850/1000 in fact all, the later year inlines wi th ehalf twist knob all have intechangable faceplates, I put a 63 1000 faceplate right onto my neighbors 84 1150, with a set of 1000 cowl decals a double take would be needed!
Randy

Thom, you are the master but I think you will find that the 1100 versions or the 93 cu in blocks are set up for the 65 and up mids that have the inner cowl supports and will not fit onto the 64 earlier versions that through bolt everything. The 1100 blocks are cast different on the bottom. This lower block configuration changed yet again late 60's or early 70's depending on size motor.
Randy

63G3,

Thank U for the detailed post.
Lots of great swap info that's not on Web anywhere... And takes years of experience to figure out.

The Mark 75/78 is a beautiful face, but 100hp performance would put a bigger grin on my face.

So, thinking the Merc 700 is very classy looking engine and 100hp would pull salom skier with Capri boat.


Would the Merc 700 faceplate fit on hat & cowling of 1000 ?