twister variations

[mk55]

What is the main difference between the twister 1, 2 and 2x. and were these considerably more motor than the bp series.

[Mark75H]

5 or more motors, not 3


The Twister family starts out with a prototype called the "Cowbell" Twister that did not return the exhaust to the driveshaft housing, but instead let the exhaust exit thru 2 rectangular megaphones beside the driveshaft housing.

The 4 production customer motors were the Twister, Twister-1 (dash one), T-2 and T-2X.

Merc did not claim a major top end horsepower increase for the customer Twister over the open stacked customer 1250 Super BP which was claimed to be 155 hp in advertising, but - Merc did claim that the Twister had more mid range power than the 1250 and that puts you around the race course much faster. These first Twisters had red 1971 style decals. At about 150 hp the left hand version of the Merc Super Speedmaster with the double sided propshaft gear between the pinion gears could not stand up to use in marathon racing. There were 2 solutions to this. One was to use the tooling for the first (and unused) Mercruiser SSM to make a heavier SSM for the Twister. The second was to reverse the whole motor and use a left hand prop ... special starter & throttle/advance linkage for a counter clockwise running powerhead.

The Twister-1 (dash one) is a minor improvement over the original customer and got the dash one suffix. This was the way Merc designated a minor improvement to an existing model ... adding a dash one to the original model name. Some people claim that early dash one Twisters had the same decals as the non-dash one Twisters, but all Twisters with blue decals are certain to be dash ones.

The Twister and dash one both used normal 3 carb fronts and modified wrap around cowling.

The T-2 motor is a completely new motor based on a different prototype. Instead of 3 carbs feeding internal reeds they used 6 carbs feeding reed cages in front of the crankshaft. Early prototype versions of these used custom made carbs with rectangular throttle plates and were known in house as "C-6" motors ... for the 6 carbs. With the reed cages and carbs pointing way out the front a completely new cowl was needed. The one piece C-6/T-2 cowl rests on towers on top of the motor and is secured with pins. Some late prototype C-6's were decaled as "Super Six". The T-2 mid section resembles a BP tower but has big bosses to accept steering bar and the 1972 & later powerhead pattern. Power is a big jump to about 170 hp. One major change at this point is that there were practically no boats using 2 motors as was common with the BP's and early on with the Twisters and dash ones.

The T-2X is again a different motor. Filling in for the now yet ready V-6 the T-2X uses the smooth sided T-3 mid section with an adapter and rubber hold down straps to secure the hood ... just like a T-3. The T-2X powerhead does not have cowl support towers inside, it straps down tight to the base cover. Power output claimed for some race team motors was in the 200 hp range, but customer motors were a bit less, probably 180-185.

[Raceman]

The first Twisters (red striped) had a slightly different mid section with the exhaust log bolted to an adapter which was bolted to the mid. The Twister (blue striped) had the log bolted directly to the mid. There were also offshore Twisters in this time frame that had minor differences, such as full gearshift lowers, and I've heard claims of 20" ones, although I've never seen one. There were also differences in the way the wiring harness was installed on the offshore engines, allowing the engines to be mounted closer together on multi engine boats. Back to the differences in Twister/Twister1, the block, switchbox, exhaust log and dozens of small parts were different. There are slight differences in port timing between the Twister and Twister 1, although I don't have accurate specs.

The Twister 2 and T2X were VERY different from the Twister/Twister 1. The Twister and Twister 1 had the OLD bolt pattern at the base of the powerhead, meaning the blocks were derived from the old 70/71 1150/1350 block design (as was the Super BP in 1969 which was the first direct charge Merc) The Twister/Twister1 were 3 carb engines, while the T2/T2X had 6 Tillotsen carbs and 6 horizontal reed blocks as opposed to the shared on crank 3 reed blocks of the ealier Twisters. (First T2's had Murrey carbs, but that didn't last long) Although there were apparently some internal changes in the powerheads between the T2 & T2X, they were basically the same. The MAJOR difference was the T2 was on a mid that was the same lenght as the shortshaft inline std engines and the T&T1, while the T2X was adapted to the new T3 V6 race mid that was a FULL 5 inches shorter still.

With the exception of the offshore Twister and Twister 1, all of the Twisters came with Speedmasters of one design or another.

A lot of people don't realize it, but the T2 was designed AFTER the T3 V6 race motor was already done, in prototype form at least. I've heard a couple of different opinions as to WHY they even built this engine since the V6 was so superior in so many ways. Some people felt it was giving the privateers something to run until the V6 was completely debugged and in sufficient quantity to make generally available past the needs of just the team boats, while other people feel that they hoped that a hundred cubic inch race class would continue even after the Mod U class went up in cubic inches.

The T2 & T2X were also the only inline 6 Merc ever to be factory built with an aluminum flywheel, although the T2 flywheels have since been retrofitted on everything from 1500's to Twister/Twister1's.

The T2 & T2X also were the first Mercs to have the one piece plastic lift off cowl. The T2 cowls were retained with 3 automotive type hood pins through the top and the T2X had the rubber bungies like Merc continued to use on all the light one piece stuff prior to the Alian cowls.

[mk55]

Thanks guys, this all goes in my racing merc files, anything up through the inline 6,s never had a love for the v-6's, two many around I guess.
Did merc ever give any info as to what kind of hp these twisters developed.

[Mark75H]

Twister And Dash One: 160-ish

T-2 170-ish

T-2x 180-20012345

[largecar91]

Keep in mind that as Mark 75 said, you could have 2 of the same engines with totally different porting. The factory team motors and some of the privateers had some very radical porting in some of these engines.

[T2x]

Keep in mind that as Mark 75 said, you could have 2 of the same engines with totally different porting. The factory team motors and some of the privateers had some very radical porting in some of these engines.

Also very different pistons and rings.....

T2x