Turbo charging a 2 stroke outboard

[Kevodaniel]

I have come across some small engine turbos that will support 100 hp has anyone tried this if so what was the outcome I'm thinkin about tryin it on a 99 40 hp johnson it seems easy enough to hook it up just trying to figure out boost preasure and jet size to get the perfect air/fuel ratio with out destroying it any thoughts or suggestions

[champ20B]

I have come across some small engine turbos that will support 100 hp has anyone tried this if so what was the outcome I'm thinkin about tryin it on a 99 40 hp johnson it seems easy enough to hook it up just trying to figure out boost preasure and jet size to get the perfect air/fuel ratio with out destroying it any thoughts or suggestions

You would need to rig up an oiling system, separate. It would require regular auto engine oil. You could probably do this with a diaphragm pump as long as the oil is cooled by a separate water jacket as it is recirculated or use an electric fuel pump. Also, it would not be a bad idea to cool the induction between the turbo outlet and intake with a water jacket as well ( intercooling system ) to densify the charge.

The early Detroit diesels that trucks and other industrial applications used were two cycle. They had a roots type blower that pressurized the engine intake. When the piston reached bottom, the pressure would scavenge the cylinder while the exhaust valves opened briefly. Then the valves shut and compression took place. When the compression was maxed, a mechanical injector sprayed fuel in and combustion occurred ( no glo- plugs. it cranked under compression alone!). Later on, a exhaust driven turbo was added to the blower for better power, which proves that a turbo can be driven by the brief action of two cycle exhaust.......

[LittleCharger]

Tim Kurtz is the guy to talk to, he's on here.

http://www.boatracingfacts.com/forums/showthread.php?13172-Tim-Kurcz-Turbo-charged-outboard-viewing&highlight=Turbo

[Kevodaniel]

You would need to rig up an oiling system, separate. It would require regular auto engine oil. You could probably do this with a diaphragm pump as long as the oil is cooled by a separate water jacket as it is recirculated or use an electric fuel pump. Also, it would not be a bad idea to cool the induction between the turbo outlet and intake with a water jacket as well ( intercooling system ) to densify the charge.

The early Detroit diesels that trucks and other industrial applications used were two cycle. They had a roots type blower that pressurized the engine intake. When the piston reached bottom, the pressure would scavenge the cylinder while the exhaust valves opened briefly. Then the valves shut and compression took place. When the compression was maxed, a mechanical injector sprayed fuel in and combustion occurred ( no glo- plugs. it cranked under compression alone!). Later on, a exhaust driven turbo was added to the blower for better power, which proves that a turbo can be driven by the brief action of two cycle exhaust.......



I have thought of an oiling system I think a windshield washer pump would work if I used thin oil like 0w 20 or or like you said the exhaust I would take the exhaust plate on the side of the motor build a identical one with a hole cut out In the middle with a pipe and flange to bolt turbo to and run a intake into two carbs without inter cooling it shouldn't be much heat produced only running 5 or 6 psi of boost

[champ20B]

PLEASE REMEMBER THAT MODIFYING ENGINES CAN BE DANGEROUS AS PARTS CAN FAIL AND ENGINES CAN PROBABLY BLOW APART DOING THIS!..... One more thing though to correct myself earlier after meditating on the mechanics of this, a diaphragm pump will no longer work if your motor is a two stroke and equipped with such. Your crankcase will be under constant pressure once the turbo is wound up. You would need an electric pump for fuel and one to circulate oil to lubricate your turbo.

Furthermore, you need an extra surplus powerhead(s) for experimentation. You need to set up an adjustable pressure relief from your turbo feeding the motor. You need a pressure guage there to note how much pressure is in the intake that you can go to before the test engine fails. You would also need a fully adjustable carburetor because fixed jet carbs aren't worth a crap when you start modifying. A slightly rich mixture to start, is a must, and can only be promised with a fully adjustable unit of some sort. Again, this can be risky to do.....that's all I can say for any input. Good luck!

[champ20B]

I have thought of an oiling system I think a windshield washer pump would work if I used thin oil like 0w 20 or or like you said the exhaust I would take the exhaust plate on the side of the motor build a identical one with a hole cut out In the middle with a pipe and flange to bolt turbo to and run a intake into two carbs without inter cooling it shouldn't be much heat produced only running 5 or 6 psi of boost

You may need a "filler block" to go between the exhaust ports and the plate. This would likely need to be a "wet block" that is water cooled unless dry blocks are used. They bridge exhaust from your ports to the exhaust cover to go into the pipe(s) for efficient flow.

The guys that run modified OMC engines can help you with that if such is used and/or available. I believe they do race this engine or one similar with good success. Filler blocks are typically used where megaphone pipes or expansion chambers are permitted in modified class racing.

You will need to have a oil canister to run 30wt or close. This is just to lubricate the bearings in your turbo alone. You need a petrol rated pump to recirculate it. This oil will get hot as hell, so the canister needs to be cooled to preserve the bearings in the turbo. The charge will get hot too, though cooling that may be optional, this will give the engine more power.

Most importantly!!!!! If your engine is a VRO (variable ratio oil injection), get rid of it. You will need to premix your fuel at about 25:1 just to be safe for such a power increase. That's what OMC "A" motors use. Penzoil is the best in my opinion.

[Kevodaniel]

All considered but I'm not looking to make big power just lookin for 15 to 20 hp as for more fuel I was thinkin my stock 50hp carb has 55d main jet change to a 60d jet with a adjustable wastegate turbo start at 2 psi make a pass on fresh plugs check the plugs color and go from just looking for a simple bolt on system nothing crazy

[champ20B]

All considered but I'm not looking to make big power just lookin for 15 to 20 hp as for more fuel I was thinkin my stock 50hp carb has 55d main jet change to a 60d jet with a adjustable wastegate turbo start at 2 psi make a pass on fresh plugs check the plugs color and go from just looking for a simple bolt on system nothing crazy

That would likely be a good approach to start with, as far as checking the plugs for fuel rich/lean mixture if a fixed jet is the goal. Starting out low in pressure would be safe, though you may get over (1.5 HP) per cubic inch with ease if the turbo is working good, with slightly bigger carburators..... A (15HP) increase can be easily obtained with this motor with much milder mods. Even if using a mild turbo, it is feasible that it can do a good bit more. The 40 OMC is a good reputable engine to build up from. It can probably take on or beat a Merc 500 in stock form. The internals are quite stout in appearance as well. I cant think of nothing else to say... If you plan to do this project though, I'm sure it can work pretty well. It would be the talk of the lake for sure!! Have a good one!!

[Kevodaniel]

That would likely be a good approach to start with, as far as checking the plugs for fuel rich/lean mixture if a fixed jet is the goal. Starting out low in pressure would be safe, though you may get over (1.5 HP) per cubic inch with ease if the turbo is working good, with slightly bigger carburators..... A (15HP) increase can be easily obtained with this motor with much milder mods. Even if using a mild turbo, it is feasible that it can do a good bit more. The 40 OMC is a good reputable engine to build up from. It can probably take on or beat a Merc 500 in stock form. The internals are quite stout in appearance as well. I cant think of nothing else to say... If you plan to do this project though, I'm sure it can work pretty well. It would be the talk of the lake for sure!! Have a good one!!


What mild mods are you talkin bout only other thing I know would work is put a 50 hp head on and shave it thanks for your help

[Bill Van Steenwyk]

Right up front, I have no personal experience with turbos on a 2 stroke. I would strongly recommend Tim Kurz as someone who has experience in this type build.That being said, the most successful turbo applications come with electronic ignition, electronic fuel injection, and other controls to manage engine function and paramaters during the RPM range that the engine is operating in. I have had a number of cars since the early 80's that were turbocharged and have some knowledge as how they were successful.

For example at the turbo builds boost, if the compression ratio stays the same, detonation can occur as compression pressures rise as the turbo builds boost. Unless some way is provided to take care of this such as reducing timing BTDC and/or enriching the fuel mixture, much damage can be done. These are changes that need to be done as the engine is running up thru the RPM and load range and that is why most successful turbo/supercharging applications on cars available to the general public have been done since the widespread use of electronic engine controls became available.

In the mid 80's a company called Land & Sea came to a Kilo trial in Moorehaven Florida with 2 V-6 Mercs, one turbocharged and one with expansion chambers. Many problems were encountered during the attempted runs, burned and stuck pistons and other associated problems. I asked one of the engineers on the project what had been done to provide adjustment for the problems mentioned, and had the stock electronic ignition and fuel injection been reprogrammed to take into consideration these changing parameters. He looked at me as if I were nuts. "What do we need to do that for" was the answer I got. My comment was look at the problems you are having and think about it for awhile, take into consideration what causes these type problems and then take steps to remedy them such as enriching the mixture, lowering the compression ration, backing the timing down, etc. That is where an electronic method of doing these things can solve many problems as these adjustments can be made while the motor is running thru the RPM range, instantaneously.
As far as oiling the turbo, this can be done by tapping some crankcase compression to force oil from a small container and oil the bearing with a total loss system and then refill between runs as needed. Some type check valve might be needed in the line.

The above problems and ways to solve them (electronics) are the main reason turbos have become one of the ways, that auto manufacturers especially, are solving problems such as more power when needed from a small displacement engine, fuel economy measures, along with emission requirements. One of the stock Merc engines sold presently is supercharged and most certainly has electronic controls to adjust the various things mentioned.

In short you have a very good method to accomplish all the above, but it must be able to be controlled to overcome problems as the RPM and power increases.

Again, Tim Kurz who is on this site probably has more published experience with this than you will easily find anywhere else, and could probably be a big help if contacted.

[champ20B]

What mild mods are you talkin bout only other thing I know would work is put a 50 hp head on and shave it thanks for your help

Actually, your engine is a 44.9 cubic inch two cylinder. The 55HP version was of the exact same specs with only a few minor changes. I don't know what they were, but an OMC parts manual might be something that could clarify what parts were different.

[Kevodaniel]

Ecotrons make a 2 stroke fuel injection kit and can be used for boosted applications it's 500 dollars pretty sweet lookin setup look it up

[Kevodaniel]

Actually, your engine is a 44.9 cubic inch two cylinder. The 55HP version was of the exact same specs with only a few minor changes. I don't know what they were, but an OMC parts manual might be something that could clarify what parts were different.

I have the 50 hp carbs and boysen reeds on my motor the other things that were different was the head carbs and exhaust tuner