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Thread: Merc V6 History
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07-21-2013, 07:50 PM #1365000 RPM
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Having calculated the balance situation for each of the crank pin arrangements and considering how those arrangements affected the requirements for crank strength, I picked one crank for the 60°V and one for the 180°V.
The one I picked for the 60°V was not the one with the best balance, however it does have adjacent rods on the same pin which makes the crank stronger, stiffer, and easier to machine, and allows for less bank offset which reduces size and weight. The balance was still somewhat better than that for our production in-line six. This crank also fired both banks from top to bottom or bottom to top which I felt might have beneficial tuning effects.
The 180°V crank chosen was the one with the lowest out-of-balance because the others were seriously out-of-balance. However it does not have adjacent rods on the same pin. Rods 1 and 2 are 120°apart, 3 and 4 are on the same pin, and rods 5and 6 are 120° apart. Also, one bank fires up, the other down.
Having made these basic decisions, a rough layout was made of each engine to determine overall size and also to investigate possible difficult details regarding the plumbing of exhaust and inlet systems, cylinder porting space requirements, sealing arrangements between crankcases, center main bearing support, and counterweighting means.
Certain advantages were found to be inherent in each design. These were:
60°-V6
1. Strong, stiff crank easy to machine
2. Fires both banks in same direction.
3. Exhaust is compact and flows smoothly into driveshaft housing. Easier to
tune exhaust.
4. Exhaust system has fewer parts and less machining.
5. Height and width are about the same as Opposed but length is 2 to 3 inches
Shorter.
6. Intake system is shorter and more direct.
7. Weight should be a little less.
180°V6 (opposed)
1. Inertial balance is better--.87 vs. 1.20.
Probably the biggest negative for the opposed engine was the difficulty of routing the exhaust from the front bank back into the driveshaft housing.
It was obvious, the 60°V was the way to go. So we (Al Tyner and I) started the detail layout. This would have been about May1970.Last edited by rckid74; 12-30-2017 at 11:37 AM.
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07-21-2013, 10:29 PM #137
So, you never considered the paired opposed design (3 crankcase sections rather than 6?) as used by Konig and some others?
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07-22-2013, 06:12 AM #1385000 RPM
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07-22-2013, 03:54 PM #139
Opposed cylinders on 180° crank pins, firing together. That's the way the antique opposed motors were set up and the way Dieter Konig built a few 6 cylinder race motors in the 60's (based on extension of his 4 cylinder boxers). It would seem like it would have a great volumetric efficiency advantage on a 2 stroke.
I understand the exhaust plumbing issue with the opposed motors; I would have solved it by not taking the outlet off the bottom, but I can see that the boxer would still stick into the boat more than other designs.
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07-22-2013, 06:39 PM #1405000 RPM
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Firing opposed cylinders together doubles the peak torque on all the driveline components and would require much beefier components, especially the gear set. It was estimated that the torpedo diameter would have to increase by 20-25% for equal life. I had eliminated this possibility when I required only even firing orders. I.E. 60-60-60-60-60-60-. Other than that, handling the exhaust from the front bank, as I said before, would be ugly. Dieter always just had tuned pipes jutting out in all directions which was fine for the racing classes but would not be acceptable for a production engine.
Why would your setup have any greater volumetric efficiency?Last edited by rckid74; 07-22-2013 at 06:58 PM.
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07-22-2013, 08:45 PM #141
The internal tuned 3 cylinder stuff is running away from the external tuned pipes in Mod these days ... pretty sure I've figured out what the guys are hiding inside their neatly polished 3 cylinder exhaust housings ... to bring 3 pipes to the same length, 2 (1 & 3) run immediately to the front, the third (cylinder 2) first runs to the back, then turns around and goes the front - giving the same lengths at the point of convergence
Seems like the 2 pistons coming toward each other (& the crank) decreasing the crankcase volume from both sides at once could give a high primary pumping ratio
Now I understand about the high peak torque, Dieter built a double driveshaft lower unit for the 6's and still had a lot of trouble. It also explains why I've been getting away with smaller lower units running a 6 against the triples and why the triple guys are absolutely punishing lower units.
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07-23-2013, 05:57 AM #142Member
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this is great. I am getting ready to buy a 2.5 mariner and find it absolutely amazing to see the history of this motor unfolding before my eyes.
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07-23-2013, 09:37 AM #143
this is great that all these different guys are coming out an sharing there own part in this keep it coming
79 Baja 18ss merc 2.5
94 trophy 2352 (sold)
85 checkmate enchanter merc 2.5
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08-05-2013, 08:23 AM #144
Anything new about old blue?
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08-13-2013, 05:26 PM #145
This thread is so fantastic and so important that I felt it really needed to be pinned to the top of this forum, so everybody will be sure to see it.
Thank you to all of you that have contributed to this incredible resource of information.
Greg
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08-13-2013, 05:40 PM #146
I couldn't agree more Greg!!!
BUT???
Why did it stop all of a sudden is my question? The two guys that were originally involved were on a roll and simply stopped? I hope it wasn't because of everyone bombarding them with questions before they finished their history of the Merc V6.
Please continue RCKID74 & JFL. Please!!!!!!!Bud Conner "Heathen" "Defending Our Constitution"
FOR ALL ENGINE APPLICATIONS
DRY Film Lubricant for Piston Skirts & Cranks + Thermal Barrier Ceramic Coatings for Piston Tops, Combustion Chambers, Valves etc !!
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08-13-2013, 05:59 PM #1475000 RPM
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08-13-2013, 06:25 PM #148
How about if we make them honorary Heathens????
Maybe they're just on vacation.Living in the Freedom provided by Bud Conner and his fellow warriors.
R.I.P. my Heathen Brother
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08-13-2013, 09:26 PM #149Scream And Fly VIP
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I've been holding off saying anything really hoping the moderators would act appropriately.
I hope it's not a health issue with Jerry.
But it's a Merc V-6 thread and people are asking why you didn't design it like this or that, how did you figure this when it was previously covered in his prior posts.
I felt some of the posts were insulting to the engineer who created this engine. Ever notice the ones with the most knowledge end up not posting? Here we have the designer of the Mercury V-6 willing to tell us the story and rather then letting him post the story people are taking it off track. Maybe this impresses themselves but I and many others were thoroughly enjoying the history and the story.
Jerry I hope all is well with you and I hope you continue. If you do start to post again I hope the moderators can keep it on track and allow you to tell the story without a bunch of BS.
There I've said my piece and anybody who wants to bash me for it have at itLast edited by Onetime; 08-14-2013 at 06:31 PM.
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08-13-2013, 11:56 PM #1501980 Cougar 19 tunnel,90 2.4L Bridgeport EFI in middle of restoration.
1988 BAJA Sunsport 186, 96 225 Pro Max
79 12' Auminum, 95 Merc 9.9
RIP Stu
"So many idiots, so few bullets"