Ok you old salts...Merc question

[Texasmark]

Was surfing old Merc sites. Question came to mind.

Back when the first tower came into being it was a 60 hp and 99.4 cu in (as I recall). That was '57 or somewhere around there. 25 years later the same powerhead is putting out 150 hp with the blue band, with the old hp ratings (brake hp just like the original) just prior to the V6 introduction.

Hard to imagine that technology made that much difference in that engine.

Looking for answers guys and gals.

Mark

 

[Chinewalker]

Re: Ok you old salts...Merc question

The first 6cylinder inline was nowhere near 99 cubes. It was a 60 cube powerhead. There are those who would say that Mercury only designed one motor back then - the 1947 Mercury KE7 Lightning, 20 cubes, approx. 14 horses. They then modified that basic design to build every other motor in their line for the next 25 years until they came out with the V6s in the 1970s. They essentially scaled it up for bigger bore models, stacked them for taller models, etc. Same basic short stroke, small bore philosphy.

That said, the 1957 Mark 75, 60hp, was essentially three of the 20 cube (by this time rated around 20 horses) powerheads stacked. In reality, Charlie Strang cut the top and bottom cylinders off a pair of 4-cylinder blocks, welded them together, did the same with a crankshaft and built the first prototype 6cylinder. Carl Kiekhaefer stated that it spoke with authority - build it!
They added a bit to the bore for 1958 and upped the cubes to 66 and horses to 70 for the Mark 78. They did it across the line in that family, with a 22 cuber and 44 cuber being added. Mercury did a lot of that modularity in their design philosphy. Kept costs down, I suppose, although Merc was usually the priciest motor back in those days... I suppose Karl was too busy racing Chrysler 300s and starting what we now know as modern NASCAR racing...

If you haven't already, read Jeff Rodengen's two books on Mercury - "Iron Fist" and "Legend of Mercury". Lots of good stuff in them... and as Charlie Strang told me, it's all TRUE!

- Scott

 

[rodbolt]

Re: Ok you old salts...Merc question

the 1500ss inline of the late 70´s was running bigger carbs,bigger reeds and larger transfer ports and boost ported pistons, also had high dome pistons and somewhat higher compression than most the rest of the inlibes.
it also came apart more often as it tolerated NO subsystem degradation what so ever. however when they was good they was good,
had a friend that regularly spun his at 8500.
he used a pair of OMC CD amplifiers and the old style duel point kiekiefer distributor.
TRW single ring pistons and special custom built reed blocks.

at the same time another friend was running a highly modified 75 3cyl jonnyrude block on a homemade midsection and homemade gearcase with a homemade prop.
no flywheell and a homemade hot head with a homemade operator adjustable expansion pipe for exhaust.
they used home made cylinder finger porting and modified single ring TRW pistons.
ign was a custom ground cam indexed to the crank key and 3 sets of points fireing 3 battery CD amplifier boxes and 3 ign coils.
while actually dialing it in for max speed the lst race Ron ran he set the altidude record on the nnsmond river and almost died, the hul was rebuilt and sold. Ron still has the engine.
his estimated speed at the time of becoming airborne was 115MPH. not bad for a 3cyl on a 13ft plywood hull at 9200 RPM.
he did find out that day why when ejected he always ended up back in the boat. seems as the boat continued horizontaly he slowed down,until the boat went verticle and he reentered it. thats what hurt him.
he said he got to watch the closing with the hull in slow motion.
then went through the front deck head first.
cant beat a bell toptex .
but yes the inline 6 merc went through some amazing technology changes from the mid fifties to the late 80´s.
some good others not so good.
my opinion of the hall effect trigger used on the thunderbolt system is not worth discusing.
the funniest of the six´s was the old dock busters. had a customer with a pair of them for years.
hated them.

 

[BF]

Re: Ok you old salts...Merc question

interesting stuff... but Texasmark's original observation still stands... they went from about 1 hp per ci to something around 1.5 hp per ci in the final 150 I6... pretty amazing.

If my calc's are right, my early 80's V6 150 is about 1.17 hp per cubic inch... Maybe its relatively mild state of tune is why it's still alive and well. (?)

Of course all this assumes the hp numbers are correct. Maybe I'm a sceptic, but I've always wondered whether the factory hp ratings are all that accurate to start with. Maybe the average factory released I6 "150" weren't REALLY 150 hp... or maybe my V150 is a conservative 150... (build the legend of the "black max") Anyway, I could see why a manufacturer might want to fudge those numbers a bit. (to fill in a model line, or have a ski motor that is stronger than the competitions)

Yes, I realize there is real hp testing involved, but surely there is potential for some "tweaking" or "de-tweaking" in order to make the test motor land where you want the rating to be (?).

Anyway, like I said, interesting stuff. Thanks for sharing the stories.

 

[rodbolt]

Re: Ok you old salts...Merc question

only observation is the blocks from the early 99 cube motors were NOT the same as the 1500 99 cubic inch motor,neither was the carbs,reed blocks or pistons. the same holds for the 2.0L v6. its been made from 135 to 220 HP. the 2.5 was mostly 200 and 225 but some 300 hp versions have been made.
however just like all other industries it holds there are so many horsepower hours in a given casting, you can have a little for a long time or a lot for a short time.
the old 350 chevy in 1970 is a good example. one version was about 180 Hp used in 4 door granny machines the other was bout 325 HP used in the lt1 corvette stuff.
both shared many many casting components yet cannot be compared.
the 1.9L honda motor in fourmula 1 makes about 600 HP but doesnt live long, the 1.9L in a 4 dr grocery getter will go 200K plus miles with only maint.
having run and owned both a late 70´s 1500 and a late 70´s 1150 I can tell you from experience the 1150 will out last the 1500.
but on a 17ft cajun the 1500 was a blast .
had the 1500 apart on the bench a few times, never had a problem with the 1150. the 1500 tolerated no fuel problems of any type nor any degradation of the cooling system. changed the water pump in the 1500 twice a year and every other year on the 1150.
my opinion the best of them was the early 80´s 90 hp with ADI ign.
was about as forgiving and bullet proof as an outboard could be.
luckily for me salt water has eliminated all of them in my area.

 

[Laddies]

Re: Ok you old salts...Merc question

The first inline 6 was designed by Charlie Strang and put into production in1957 it was 60 cu.in the prototype engines were made by sawing 2 Mark 55 engines in half the bottom cly was cut from one and the top from the other the two blocks were welded together and the same was done with 2 cranks. The reason for direct reverse on the engine was OPC required a engine to have reverse so Carl Kiekhaefer got by the rule and could run speedmaster (Quicky) lower units on the Mark 75H engines They were 60 cu. in. and rated 60 HP+

 

[Texasmark]

Re: Ok you old salts...Merc question

Well, thanks guys for the info. You know, there are a lot of gutsy folks out there.....like Karl and his crew sawing blocks in half and cranks and all... d ,and others that race, trying out all sorts of contraptions to get the lead on the competetion.
--------------------
One thing I didn't understand for a long time was the relationship between OMC and Merc on hp ratings. I thought that OMC rated their engines at the prop back in the early days but reading www.old-omc.de sales brochures from the time indicate that they advertised BRAKE hp. Well, brake hp is defined as powerhead hp and that is where Merc measured theirs too as far as I know, back then.

So I think, after reading the brochures, that the reason the OMC engines, (primarily talking about 25, 30, 33, 35, and 40) pushed bigger boats faster than the Mark 30 was the fact that they had many more cubes......

What about that?

Or was it partly because of their 2 bladed prop vs a 3, or the gear ratio of the engines of the time. Surprised OMC turned their props as fast as they did back then. Don't know what gear ratio Merc was using on the Mark 30 and Mark 55.

Thanks,

Mark