Merc 200 On Boost!!! Turbo?

[SPECTRE racing]

i want to turbo a 2.5 merc. thinkin about makin the header from the tuner plate up out the side of the mid and mount the turbo. then make a draw through intake with a 650 holley carb.will my idea work?? im also wondering about building a sheet metal intake around the factory carbs and making a blow through system instead of draw through. any ideas would be greatly appreciated. will it work???

[kiaer4me]

I'm 32 and been around boats my entire life I have never heard or seen of a Turbo on an outboard. I know the 2.5 merc is an easy mota to hop up.

[Fast Fred]

most of the charge Will just go out the exhaust, it will work some what, but for the work the payoff is POOR. NOS works, far better payoff.

[Mark75H]

most of the charge Will just go out the exhaust, it will work some what, but for the work the payoff is POOR. NOS works, far better payoff.

That happens with a mechanically driven blower but doesn't happen with a turbo ... the problem with a turbo is keeping the mixture correct for the flow & load.

There have been several more or less successful turbo V-6's ... search function should bring them up. NOS is certainly less bulky and easier to guess at the mixture.

[Hydrovector]

Land and Sea made a kit years ago there usec to be pictures of one on here do a search.

[1BadAction]

fuel management would be a nightmare. a much cheaper time bomb with similar power increases would be nitrous.

either way, the subject has been beat to death on older posts.

[Raceman]

Even with a turbo you're still gonna have tremendous loss out the exhaust port since there's no way to close it during the intake cycle like on a 4 stroke. It's true that the fact that the turbo somewhate pressurizes the exhaust side does effect it, but it's still relatively inefficient. It's been tried and abandoned a lot of times by a lot of smart people. Years ago I bought a book on turbo charging. It was a general book, similar to the "how to build a big block chevy", etc, that was sold by some of the supply houses like Summit. It made the comment that the only way to effectively turbo a two stroke was to put a scavenger valve in the exhaust, but didn't give any further details.

I think you'll end up with a pile of parts and a bunch of spent money on an abandonded project if you go with it.

[1BadAction]

depending on the turbo, the hot side will have 2 to 4 times the pressure that the intake side sees. "blowing" boost out against more pressure is impossible, (I would be more concerned with reversion into the chamber from the exhaust side, which is an issue with some turbo cams in 4 strokes) another problem is, the heat that is created in an already hot combustion chamber, and controlling the fuel mixture. you will never see a carburetor do it good enough to keep a 2S from melting down, and until the past 8 years, normal EFI wasn't nearly sophisticated enough.

With a wolfe EFI (or motec, etc), e85, and the right turbo, it can be done good enough to not melt down every trip out. The problem is, you're going to go through a bunch of expensive wide band O2 sensors and most likely multiple powerheads (and turbos) to get a base line fuel map.

[Hydrophobic guy]

I've built all kinds of boosted 4 stroke stuff and currently contemplating turboing my 504 BBC. A two stroke is a different animal I had a turbo Mach Z sled after getting the bugs worked out it went like a scalded ape. I attached the link to the outfit that made it. Call them they do alot of custom stuff and they'll tell you if its feasible.
http://www.aerocharger.com/

[malexie]

The first photo i ever saw of an Allison had a merc with a Turbo on it. At the
time it was the world record holder for speed on a v-hull. You guys remember that?

[STV_Keith]

The L&S Kit from the mid 80's...

[1BadAction]

The L&S Kit from the mid 80's...

great picture... Notice the hose off the bottom of the turbine. looks like its feeding the bearing oil from the exhaust. I remember another 2-stroke turbo that did that. amazing how far turbos have came since then.

[STV_Keith]

i want to turbo a 2.5 merc. thinkin about makin the header from the tuner plate up out the side of the mid and mount the turbo. then make a draw through intake with a 650 holley carb.will my idea work?? im also wondering about building a sheet metal intake around the factory carbs and making a blow through system instead of draw through. any ideas would be greatly appreciated. will it work???

I would not want to use a common plenum, especially a wet plenum, with one of these motors. If you look, all of the motors either use a dedicated carb per cylinder or bank, or are crankcase injected. EFI is the only way to make it live IMO. It would be quite an undertaking to do.

[ken medendorp]

Dan pheltenburg from Gunlake mich Did a turbo 2.5 efi .He had to use bigger injectors and run alcohol to keep the heat down.500 Hp. Fuel curve was done on the dyno ,every 500 rpms I beleave.Not sure of the boost or Ecu that was used.

[Mark75H]

I think the drag race curve would be easier to set up than pleasure use.

Intake pressure can be higher than exhaust pressure ... because the volumes are not the same; after combustion the volume of the exhaust is larger due to the change in the physical properties of the new chemicals and the new temperature ... tremendous change in volume. The larger volume of exhaust gasses exiting the turbo can make the compressor side pressurize its smaller (pre-combustion) volume to a higher pressure. "Can" is the important word there. Since it can but doesn't have to, we can make the rest of a 2 stroke motor (actually any motor) run completely as if it were inside a pressurized warehouse ... at almost any pressure (because a little bit more in always means more out ... ) from atmospheric up to the detonation or crank train limit. Pressure rises on both sides of the motor, not just the intake.

So lets say that we have a 2.5 turbo'ed to flow 3.5 liters of air in per rev at some rpm, the air and fuel will become something like 12 liters of exhaust going out. If only 90% of the charge says in, that is still more than 3.1 liters ... probably still 30% more flow than the 2.5 had without help. Compound that with the torque increase from the added pressure and you are at an easy 50% power increase.