2 STROKE ONLY!
Your Subtitle text

PERFORMANCE

GENERAL :

This will be the most difficult page to write accurately and keep up to date but also the most enjoyable for me by far.

Let me start by saying that I am not an expert on this subject by any stretch. Yes I have learned a lot but I have gotten a ton of help from what I call the "WIZARDS" in the sport/hobby.

This site, my projects, the performance improvements I've seen would not have been possible without the help from people like Al Stoker, Gordon "Monty" Montague, Wayne Taylor and many, many more.
I also owe a special thanks to my friend Jimmy Carter back in  Ohio. Jim and his Marina on beautiful Buckeye Lake was one of my first "mentors" and helped to guide me in the right direction and sold me some really pretty motors to blow up while I educated myself on what "not" to do and what was "not" covered under warranty ;)
Anyone doubting whether OMC ever built a fast motor need only coax Jimmy to pull "Godzilla" out of the barn :)

These guys are the ones behind the scenes that blow up motor after motor and break part after part trying to get that last little bit out of them. They do that so when they sell their products to us they work!

They are the "WIZARDS"!

EXPERIENCES:

What I can tell you first hand is that there is a ton of performance potential in the OMC based, loop charged V-6's.

Like most things it makes a huge difference in what parts you combine in your project as they all have an effect on each other.

Like my dad always told me as a kid when first tinkering with cars, "when you change one part in the engine it has an effect on everything else within the system" and that is so true.
Thanks Dad!

On top of this when putzing around with a two stroke engine your margin of error goes almost to zero! When I had the 250's on my Sonic I was so impressed with how well they ran stock, I thought "wait till I get done with them" ;)

Long story short, I spent one Winter experimenting. My thinking of course was...if it runs 80 stock......(and we all know stock sucks!)

Anyhow, installed nose cones sense we also know that 80 is the magic number (bull) where you "need" them, and was already running with the air boxes removed and velocity stacks on the motors so next step was to open up the exhaust.
The old saying says "to make power you need to get air in and air out."

I decided I was getting enough in (with the stacks) so I needed to open up the exhaust to get more out.

First run in the Spring (cool, crisp Ohio air) the boat lost 3 MPH from the cones and it totally ruined the efficient running attitude that it had with stock lowers. Meaning I had to run full "up" trim to carry the bow as opposed to the previous neutral trims settings at speed.

Speed parts people 1, me zero.

So the next move was to pull the plugs out of the open exhaust snouts I'd installed over the Winter.

The good was that I got all 3 MPH back that I lost to the nose cones! The bad was that it ran for two miles before running so lean that it stuck a piston, broke a rod and sawed the block in half :o

Those motors were just barely a year old!

So there, boys and girls is my lesson about the very minute line that exists between having a 2 stroke tuned just right and having a new "Sacrifice to the Gods of Speed". (see picture on another page)

OPTIONS AND OTHER BRANDS:

We all know that Merc has pretty much  "owned" the Hi Perf O/B business for the last 20 or so years and rightly so.

I have tons of friends that run the best the black company has ever built and trust me, they are amazing motors and far, far superior  for performance than what we have in stock form.

The bad is that that performance and superiority comes with a cost, and its a big one. Parts are just as bad.
Another "good" for the Merc's though is that you can "buy" pretty much what ever you want where we have to "make" ours.

I never really appreciated that until I got serious about the JohnRudes and decided to "make" a short mid section, and "install" a nose cone. You save the money but spend the time and pull your hair out doing it!

O.K., so if I haven't scared you off yet... here we go.

TEHNICAL:

As stated on the info page, first version V-6 loopers from '86/87 have tons of potential but takes as much work to get it there.

I bored one to 3.0 specs,added finger ports, did some very mild porting and turned a 30" cleaver 7500 @ 101 GPS and turned 22" drag prop 8500. All on pump gas and that motor had tons left in it.

I will also add at this point that if you want to get serious about a JohnRude, do your home work, take your time, and are careful you can make over 300 HP's in your garage, turn it 8-8500 and have it live.

If you want to go beyond that, the "Wizards" are the only ones that know how to get there and after the cost that it took for them to get there....they ain't talking!

Most of the builders agree that the '88 - '92 open decks are the best block to build off of and that is because they have better exhaust runners than the '93 and newer blocks which have smaller runner volume. That is too bad too because none of the blocks on their wish list came with finger ports. ($$$)

The '93 and up have finger ports but more restrictive exhaust passages.

Based on the above this is a good spot for you to think about the goals for your project.
That is the most important decision you will make. If you want 250 - 270 HP's and 7000 - 7500 RPM with tons of  bottom end grunt left that's easy and cheap.

You buy a '93 and up block, add 2.7 heads, intakes and carbs, raise the exhaust ports to 1.650" from the deck surface and your done!

It becomes much more difficult when you push beyond those levels.

Another consideration for a motor aimed at that level are the '01 and newer 3.3 liter blocks. I really like what I see with these and am building one right now.
They have additional cast in (behind the sleeve/liner) intake ports plus cast in guide slots in the rod slot area which do not exist in the earlier motors.

Again, you must decide how hard you want to push??? The common consensuses from the Wizards seems to be that the "wall" due to the exhaust restrictions seems to happen at about 300 HP's and 8-8500.

So again my thinking is if we want tons of low and mid range grunt and still have RPM capabilities in the 8000 range...that may be all we need. On top of this,as in playing with race cars you spend more time using torque than horsepower.
Everyone wants a motor that turns 10,000 RPM but you give up tons of low end and mid range and will be humbled by many well sorted 7500 RPM rigs!

Something else to look at is gear ratios. That is another huge positive for the black motor camp sense Merc makes a Hi Perf lower unit called a "Sport Master" that is available with many different gear ratio's they are actually able to tune their lower unit to the motor.

Incredible stuff compared to our options of any gear ratio you want as long as it's 1.86!

My current project has a Sporty lower unit with an alternate gear ratio installed. The thinking here is that if I retain as much grunt as I can, use that to turn big gears, that equals more prop speed with out spinning the motors brains out!

This same motor is getting a Wayne Taylor made "Mad EFI" fuel injection system and one of Waynes 16" mid section.

Frank II update: 11/09/08 It's alive and it's really pissed off :o 
With only 8 hrs of break in on it I am still being gentle with it but I can give you some feed back.
It is now w/o question "THE" fastest/quickest, most violent boat I have ever driven!
The tall gears I put in the l/u have NOT killed the bottom end as I was afraid of and with 25 gls of gas and a 28" prop it pulls from 1000 RPM like nothing I've driven!
Boy's, I think I'm on to something here.
The EFI system is flat amazing as well. Won't mess with the fuel curve until after break in but  with the turn of a knob you can go from making the thing "four stroke" to perfect tune.
I'll report more as I get more time/tune on the motor.
We are going to River Ranch down here in Florida next weekend (11/14/08 - 11/16/08) which is a huge Hi Perf O/B rally and we will be letting Frank play at the drag races so we'll see how he does with ZERO tune on him but plenty of raw talent :)

As of 1/08/10: Just realised I hadn't updated info on Frank since my first outing with it. We went to River Ranch with ZERO tuning on the motor. To the point that I didn't even understand the EFI system well enough to find the fuel cure for the EFI system let alone manipulate it :)
Regardless, I went to race not sit on the beach.
First up was my buddy Laser Ed and his 410 lb kevlar Laser LTV w/a full tilt 2.5 Merc. First pass the motor idled  in cleanly and launched strong although due to having no real fuel map in the computer including no "accelerator pump" setting which gives the motor addditional fuel for the hit of the throttle I had to adjust the fuel knob on the dash while driving with one hand. I'd carnk in additional fuel at the hit and then bring the knob back to zero once rolling.
Ed beat me by a boat length. We lined up, did a second pass with the same results although this time the motor was starting to load up while idling on for the start.
Next up I ran Jeff Tyners lightning quick Allison XR race boat powered by a killer 2.5 Merc.
By this time my motor was loading up so bad it was only running on 3 or 4 cylinders at the start.
It cleaned up and ran fine once I hit the gas. Lost by a solid 2 boat lengths.
Considering the state of tune in the motor, zero test time, zero set up time, I was ESTATIC with it's outing! Told Ed after our race that I ran a 20" prop intending to tun it 9K+ but it was done at 7K and free wheeled through the finish line at 7500. Had I known that I would have run more pitch and had a different out come. May not have won but would have pulled stong the whole distance instead of to half track. Also estimated giving up at least 300 lbs to Ed.
Yes, this thing has potetnial.
After finishing drag racing due to the motor loading up so bad we threw on a big wheel, a tank of gas, my wife and headed out to play with the rest of the guys. We got about 30 miles before taking the top off a piston!
After getting it home and having time to disect things here's what I found:
#1. I was running approx. 165 lbs of compression and was mixing Av. gas with pump Premium and ended up with only about 94/95 octane. Oop's, not near enough octane and detonation once again  claims another victim.
#2. The motor was loading up due to a program in the computer that dumps addditional fuel in the motor to protect it. It came from Wayne set to start dumping additional fuel at 129* and by 143* it was dumping almost 25% additional fuel in the motor! I had the motor set to run at 145*. Duh. Again, at RR I couldn't even tell you where that program was in the computer let alone tell you where it was set.
#3. In testing I couldn't get the motor to spin up and strugled for a solution. I suspected powerpack and replaced it. Wrong.
At this point I was out of money, time and paitentce. My mule boat (STV River Rocket) was starting to show the effects of sitting outside in the Florida sun so I decided to sell it while it was still worth something. This was painful as I had not yet fully developed the motor.
After the fact I used the flywheel from Frank on a customers motor for trouble shooting when I realised the reluctor ring (determines timing) had come loose and rotated out of time and was movinig on it's own! Problem solved. Of course now the motor is sitting on a stand waiting.
It's been there for a yr and who knows where it will end up next.






Website Builder