Merc V6 History

[Greg G]

The details you are giving are true history. Thanks for that!

[rckid74]

The V6 ignition system was initially intended to be the same as the inline 6, that is, with a belt driven distributor, capacitor discharge type, single large ignition coil, single switchbox, using as much hardware from the inline engine as possible. And if you look at the pictures of “Old Blue” back on page 6 you’ll see how that looked. You can tell also that we had not taken the time to put on accessory mounting bosses. The anchor bracket is a cobbled up inline 6 unit and the throttle and spark stops were not cast on but were instead a bent steel bracket. By the way, we didn’t make all that many sand cast engines. The first batch was just 3 units and they acted as the proof of concept engines. Then I believe there were two more batches of about 8-10 each. These served as the dock and boat endurance engines.
My intention was to run the spark leads down from the distributor, around the bottom of the port head, over to the exhaust cover, and then up along side each head and to the plugs. I didn’t want to drape them across the sides of the heads because of the additional width this would have added to the overall package, and I was fighting for the narrowest engine possible. This also left the back of the engine wide open and so I cast a MERCURY name with several vertical ribs onto the exhaust cover mimicking, somewhat, the Ferrari logo I had seen and admired on some of their engines. The intention was to paint the cover black and then sand the paint off the protruding name and ribs to make them stand out. Perhaps painting them white or silver might have been better. If JFL would take a picture of the back of “Old Blue” you can see what that looked like.
But alas, all that went bye the wayside when, about half way thru the program, I was informed that the distributor was to be replaced by a six coil, distributor-less system which the electrical boys had been working on for some time. That was a major blow for me and the schedule. All the drawings were done, the testing was well on its way, and now we had to reverse course. I was not a happy camper. I would estimate that the change set us back about a half year. But it had to be done so I, grudgingly, started in on it. The only logical place to mount the six coils was on the exhaust cover so there went my MERCURY logo. In the end I’m sure it was for the better but dam I hated all the extra work that it created.
I hope that if they ever go to a coil on plug setup, they put my MERCURY logo back on the cover.

[Dave Strong]

The V6 ignition system was initially intended to be the same as the inline 6, that is, with a belt driven distributor, capacitor discharge type, single large ignition coil, single switchbox, using as much hardware from the inline engine as possible. And if you look at the pictures of “Old Blue” back on page 6 you’ll see how that looked. You can tell also that we had not taken the time to put on accessory mounting bosses. The anchor bracket is a cobbled up inline 6 unit and the throttle and spark stops were not cast on but were instead a bent steel bracket. By the way, we didn’t make all that many sand cast engines. The first batch was just 3 units and they acted as the proof of concept engines. Then I believe there were two more batches of about 8-10 each. These served as the dock and boat endurance engines.
My intention was to run the spark leads down from the distributor, around the bottom of the port head, over to the exhaust cover, and then up along side each head and to the plugs. I didn’t want to drape them across the sides of the heads because of the additional width this would have added to the overall package, and I was fighting for the narrowest engine possible. This also left the back of the engine wide open and so I cast a MERCURY name with several vertical ribs onto the exhaust cover mimicking, somewhat, the Ferrari logo I had seen and admired on some of their engines. The intention was to paint the cover black and then sand the paint off the protruding name and ribs to make them stand out. Perhaps painting them white or silver might have been better. If JFL would take a picture of the back of “Old Blue” you can see what that looked like.
But alas, all that went bye the wayside when, about half way thru the program, I was informed that the distributor was to be replaced by a six coil, distributor-less system which the electrical boys had been working on for some time. That was a major blow for me and the schedule. All the drawings were done, the testing was well on its way, and now we had to reverse course. I was not a happy camper. I would estimate that the change set us back about a half year. But it had to be done so I, grudgingly, started in on it. The only logical place to mount the six coils was on the exhaust cover so there went my MERCURY logo. In the end I’m sure it was for the better but dam I hated all the extra work that it created.

Merry Christmas and thank you so much for your input!!!


Dave

[milkdud]

What a great read. Thanks for sharing.
Conrad

[rckid74]

A few words need to be said about the head hold-down screws and how they arrived at their present position. Many of you probably don’t even know that they, for the first couple of years in production, were in bosses attached to the cylinder wall instead of in bosses in the outer water jacket as they are now.
In my years at Mercury before I was given the V6 assignment, I had done quite a bit of work experimenting with piston deflector and combustion chamber shapes. To do this we used twin cylinder engines with removable heads and we had a lot of trouble blowing head gaskets. I found that the best solution was to get the head screws in close to the cylinder wall and to keep the head as stiff as possible. I was aware that screws in bosses attached to the cylinder could cause distortion of the cylinder and consequent piston scuffing and ring problems. My solution was to bury the threads down as deep below the deck surface as possible. This surrounds the threads with much more material to resist distortion than would be the case if the threads started right at the top of the cylinder. This worked well in those experimental engines but, of course, there was never a lot of endurance time put on them. That was the approach I decided to use in the V6 and we had no trouble in all the endurance testing done before production. However after production startup we started getting reports of occasional scuffing problems. Our original fix was to bore and hone the cylinders using a dummy head torqued to the block. This worked well but was costly and time consuming so the bolts were then moved off the cylinder wall to their present position. Live and learn.

[3030]

A few words need to be said about the head hold-down screws and how they arrived at their present position. Many of you probably don’t even know that they, for the first couple of years in production, were in bosses attached to the cylinder wall instead of in bosses in the outer water jacket as they are now.
In my years at Mercury before I was given the V6 assignment, I had done quite a bit of work experimenting with piston deflector and combustion chamber shapes. To do this we used twin cylinder engines with removable heads and we had a lot of trouble blowing head gaskets. I found that the best solution was to get the head screws in close to the cylinder wall and to keep the head as stiff as possible. I was aware that screws in bosses attached to the cylinder could cause distortion of the cylinder and consequent piston scuffing and ring problems. My solution was to bury the threads down as deep below the deck surface as possible. This surrounds the threads with much more material to resist distortion than would be the case if the threads started right at the top of the cylinder. This worked well in those experimental engines but, of course, there was never a lot of endurance time put on them. That was the approach I decided to use in the V6 and we had no trouble in all the endurance testing done before production. However after production startup we started getting reports of occasional scuffing problems. Our original fix was to bore and hone the cylinders using a dummy head torqued to the block. This worked well but was costly and time consuming so the bolts were then moved off the cylinder wall to their present position. Live and learn.

Thank you. Very interesting to hear the engineering perspective on the position of the head studs. I found head studs and proper torque also solves the issue in endurance applications. Here is my latest rebuild of a '76 1750 with ARP studs and later style water jackets on the heads. I assume you went to the deep water jackets for increased cooling and inside of the heads changed as well to allow for better water flow?

[Dave Strong]

Not sure why but have found studs work great on 2 and 2.4L but the few times tried them on 2.5L they seemed to not hold?? Makes no sense but that's what happened, anyone else see this???

Dave

[Dave Strong]

and PS not to take away anything from this thread, its all about history. So anything Tech should be on a different thread. Sorry my bad for even going there.

Dave

[FUJIMO]

Jerry, all the first generation 1750XS blocks that were raced(and beyond) utilized head studs with no problems. I know you didn't get involved with the first race powerheads much, so thought you would appreciate this. Thanks again, very much, for all your Merc history.

[rckid74]

The “Black Max” cowl originally was the, so-called, clam-shell type. Kind of like a clam laid over on its’ side. That is, hinged in the back with a vertical split between the two halves and a latch in front. This cowl type had been pioneered several years earlier on the M650 three cylinder and was considered to be successful. I liked it for two main reasons. First, it allowed the cowl to hug the engine closer which gave a slightly narrower overall package, and second, when removed, gave excellent access to all the engine components right down to the driveshaft housing. It was also relatively inexpensive to make. After a time in the field though, a couple of complaints cropped up. People were having trouble getting the cowl back on the engine especially if out on the water in a pitching boat. Getting the hinge pins lined up was difficult if you weren’t familiar with the setup. Also, the seal strip around the bottom would sometimes not properly engage the groove in the cowl halves resulting in leakage. And so, after several years of production, we changed to the standard top cowl, bottom pan design. A change for the better, I guess.

[Slimm]

The “Black Max” cowl originally was the, so-called, clam-shell type. Kind of like a clam laid over on its’ side. That is, hinged in the back with a vertical split between the two halves and a latch in front. This cowl type had been pioneered several years earlier on the M650 three cylinder and was considered to be successful. I liked it for two main reasons. First, it allowed the cowl to hug the engine closer which gave a slightly narrower overall package, and second, when removed, gave excellent access to all the engine components right down to the driveshaft housing. It was also relatively inexpensive to make. After a time in the field though, a couple of complaints cropped up. People were having trouble getting the cowl back on the engine especially if out on the water in a pitching boat. Getting the hinge pins lined up was difficult if you weren’t familiar with the setup. Also, the seal strip around the bottom would sometimes not properly engage the groove in the cowl halves resulting in leakage. And so, after several years of production, we changed to the standard top cowl, bottom pan design. A change for the better, I guess.

rckid74, I want to thank you for taking the time to give us all the technical information as well as the behind the scenes stories and general historical facts that so many of us have wondered about. I have thoroughly enjoyed reading your post and especially the engine technical data, some of which I understood and some I didn't...and still some I didn't understand until your posts at which time the little light in my head went off and clarity occurred.


Slimm

[wogi]

rckid74, I would like to thank you for all this neat info and the time you are taking to put it down into words for all of us to enjoy!!!!
I feel that you should be proud of the fact that your hard work so many years ago as became the mainstay and the benchmark of performance boating as we know it today!
Did you ever have any idea that you and the others you work with were engineering the marine equivalent of the small block chevy?
Sorry to take away from this tread, but I just wanted to express my graditude for what you done in the past and what you are doing here!!!!!!!!
THANKS AGAIN

[Onetime]

Everybody following this thread feels the same way about the marvelous piece of engineering you did creating the Mercury V-6.
Jerry, let us know when you would like some questions. I'm sure there are lots out there just holding back. I know I am! Only problem will be there will be lots and lots of questions.

[Dave Strong]

Everybody following this thread feels the same way about the marvelous piece of engineering you did creating the Mercury V-6.
Jerry, let us know when you would like some questions. I'm sure there are lots out there just holding back. I know I am! Only problem will be there will be lots and lots of questions.

Keep it coming!!!

Dave

[Da Bull]

I think the clam shell cowl was the best production cowl made for Mercury engines. It was light, Easily removed and offered easy access to the intire engine components. Merc threw us a curve with the horizontal front latch as it would blow off when the front plate was not in place. Easy fix was drill a 1/4" hole through the two locking jaws and install a tie strap to hold them together.

I love this thread and cannot get enough of it.

DB