Merc V6 History

[olboatman]

What a great project.....now thats outside the box!!! Any idea what they weighed? Thanks for sharing!
Gary

[rckid74]

What a great project.....now thats outside the box!!! Any idea what they weighed? Thanks for sharing!
Gary

Don't know what it weighed. We must have weighed it but I don't have any record of it.

[Rotary John]

Interesting. Kurt Ziegler at OMC designed and built an X -8 in the late 60's/early 70's.

[rckid74]

Interesting. Kurt Ziegler at OMC designed and built an X -8 in the late 60's/early 70's.

How'd that turn out?

[Rotary John]

How'd that turn out?

As I recall he was trying to put it in a package about the size of the V-4. The motor produced over 200 HP but the rods and bearings were so small, durability was poor. I was working on the 2 rotor 100ci oil/water cooled rotary at the time. We were at 210 HP and pushed a 23 ft Wellcraft cuddy cabin 53mph.

[rckid74]

As I recall he was trying to put it in a package about the size of the V-4. The motor produced over 200 HP but the rods and bearings were so small, durability was poor. I was working on the 2 rotor 100ci oil/water cooled rotary at the time. We were at 210 HP and pushed a 23 ft Wellcraft cuddy cabin 53mph.

I've liked the rotary engine ever since it came out back in the '50's. It's a shame that a number of things all came together to kill it. I've been working on my own version of it as my retirement project. This isn't a Wankel type at all, it still has pistons. See it at https://www.youtube.com/watch?v=xDmpt_Ah2RA&t=217s

[Rotary John]

The oil cooled rotary was developed as both an IO engine and an outboard. The IO version was small enough that there wasn't any dog house in the boat. The rear seat went completely across the back with the engine under it. Omc made a huge mistake by not pursuing that combination. It actually out performed a small block engine. I guess that was yesterday and it won't ever come back. I hear rumors Volvo Penta is interested in buying BRP/ Evinrude. They already have a controlling interest in 627.

[lars strom]

I hear rumors Volvo Penta is interested in buying BRP/ Evinrude. They already have a controlling interest in 627.

Well..I started that rumor last year but its still only my opinion..!!

Volvo Penta should also purchase the Evinrude division from BRP.

http://svera.se/blogg/volvo-penta-sh...sion-from-brp/

[rckid74]

But we digress!!! --- Getting back to the X12. --- I was concerned from the beginning about having those long driveshafts connecting the two engines thru two gearsets. I was afraid of torsional windup and would that result in any vibration problems and load buildup which might be noisy and even lead to failure. I felt that a gearset tying the two driveshafts together (with some preload) up close to the bottom of the engine would be necessary. But there were problems I anticipated with that -- such as keeping the gears oiled properly and noise from the gears meshing. So I decided to try it without the gears first and only put them in if problems developed.

Built up the first engine and put it on the horizontal propshaft dyno. The biggest horizontal dyno we had at plant #6 at that time was a 400HP water brake. Anticipating more power than that we made sure the overspeed was working and proceeded to open her up. Got up to 400HP at about 5200 RPM and everything looked good so proceeded. At 420 HP - 5500 RPM the dyno let go and the overspeed caught her. If we could have made it up to 6000 RPM, I think it would have made the full 450HP.

[W2F a V-King]

I've liked the rotary engine ever since it came out back in the '50's. It's a shame that a number of things all came together to kill it. I've been working on my own version of it as my retirement project. This isn't a Wankel type at all, it still has pistons. See it at https://www.youtube.com/watch?v=xDmpt_Ah2RA&t=217s

Awesome. Watching it run, and the sound of those stinger style pipes, I thought it was a two stroke until I read the caption...Very Cool!!

[rckid74]

We built up a second X12 which went on dock endurance. Dock endurance almost always consisted of running wide open throttle till something breaks --- and something broke real fast --- it proceeded to strip all the blades off the diecast prop in short order. So we switched to stainless --- which held. I forget how many hours we put on it running WOT but we never did fail anything else.

The first engine was used for boat endurance. It went down to the salt water test base at Placida, FL On the boat, a problem showed up. As long as the throttle was open enough to eliminate misfiring, everything was nice and smooth, but down near idle -- once misfiring started -- a rattle was set up -- a loud rattle. The shafts got into a resonance which rattled the gears back and forth. It looked like gears at the top of the shafts were going to be needed -- with a preload -- enough of a preload to exceed the actuating forces. But before doing that I wanted to try another idea I had. So I spent a fair amount of time with that. In the meantime, the economy took a dive, marine sales went way down and the big boys started looking for projects to kill. X12 was one of the first to go. The two engines were boxed up, sent down to the warehouse in Fond Du Lac and there they remained. 7 or 8 years later I happened to be walking through the warehouse and saw those 2 big cartons up on the third high shelf. What a shame!! They're probably still sitting there!!

Can you imagine this setup with 2-- 2.5 liter blocks set up with all the latest racing tricks -- are we talking 800 HP at 8500 RPM??

[Dave S]

Hopefully the boxes are still somewhere safe. Did the crank cover have 2 parts as to make it easy get to the main bolts?

[rckid74]

Hopefully the boxes are still somewhere safe. Did the crank cover have 2 parts as to make it easy get to the main bolts?

That's interesting you should recognize that little problem. The new crankcase was just one piece. Getting at those 4 centermain fasteners was a problem. I put studs in the blocks. With the crankcase in place, there was just enough room above the studs to sneak the nut thru but it was down in a pocket where you couldn't get your fingers in to start the thread engagement. So I made a special tool to get the nuts down in there and start them rotating, it had a ratcheting finger attached to a lever out on the handle. Once the nut was run down you could get a box end wrench in there to torque it up. Good observation there Dave!!

[Dave S]

Thank for sharing this info. Another ???? Did you cast up a new gear case or cut and weld a stock lower with 2 holes for the ds. Non/ gear shift? Because of the lower unit syncing the power heads?

[rckid74]

Thank for sharing this info. Another ???? Did you cast up a new gear case or cut and weld a stock lower with 2 holes for the ds. Non/ gear shift? Because of the lower unit syncing the power heads?

The gearcase, driveshaft housing, and adaptor plates were all new sand castings. I don't remember the hookup in the gearcase but it was fully shifting. If you look carefully in some of the pictures you'll see the shift link going forward from the anchor bracket to the shift lever on the port side of the engine. The exhaust from the front engine (as far as I can recall) split and went to the back on either side of the driveshafts. Water in came up thru the front engine in the usual way but then half of it was piped to the top of the back engine. The small electric fuel pump on the port side was used for starting only. It was wired into the start circuit. Then, once the RPM,s came up a little, the main, belt driven high pressure pump had enough pressure to take over.