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Breaking news: +.065” oversize Mod-50 replacement pistons now available!

Wiseco just approved manufacture of +.065” oversize pistons for the 49.7 CI OMC loop triple. This means you can breathe...

Hey Xpress2830,

New CNC turned with fasteners for $55 each plus $6 for a USPS flat rate box. Email tkurcz123 at gmail.com[/QUOTE]

Tim

Wiseco forged replacement OMC 49.9 Mod-50 pistons are now available. They are improved versions of the #10908 previously supplied by the late Phil McDaniel. Designed for use with the Mod-50 or...

Yep, that one's one of only three built with enclosed exhaust for harassment-free laking. Enjoy!

Tim

Hey Tumbleweed,

The OMC triple carbs come in three venturi sizes 1.125", 1.187", and 1.250". Smaller venturi's will get you stronger bottom end, larger venturi's get you better top end. These...

Good to hear from you too Cheney. Finger angle should match the boost, about 1/4" deep X 3/8" wide is about right. Tops must all match exactly to work well..... Good luck with the watering. It...

Hey Cheney,

What ports exactly are you talking about? Boost is the center (angled), then fingers (angled ala Mod-50), then transfers (90 degree entry). If you're talking about finger ports,...

Hey Cheney,

Boost is the center (angled), then fingers (angled ala Mod-50), then transfers (90 degree entry). If you're talking about finger ports, they have to be cut at the correct angle to be...

http://www.youtube.com/user/Unfairadvantage22?blend=3&ob=5#p/a/u/0/TVKRSrHZYfc

Unfortunately, the sound was disrupted by the ignition system. This was the 91 MPH run on two cylinders. Still...

Dixon and I ran boats yesterday in glorious weather, along with an overactive general public: 80F temps and opening day of duck season! We were unable to get side by side, but managed a little fun...

You're going through alot of trouble to wax my little OMC - it must make you nervous! Just took delivery of a 14 pitch Dewald that will carry 115+ 15 PSI boost and the nitromethane shoud narrow...

Hmmmmm...... Better bring 5 gal of Methanol and 25% Nitro-methane just in case. That should even the playing field, if only for a run or two! All the horses and men are lined up for Sunday 1PM at...

Hey Dixon,

Hmmmm; the math says you've got about 2.5:1 power to weight on me - yikes! So, you should be happy to spot me a few boat lengths! On thing for sure, the turbo adds enormous punch to...

Yesterday's test session was scratched in favor of demo rides as Virgo performed almost perfectly from the start. Weather was 70F+/- with a heavy overcast and mist, but no wind. All were impressed...

Not sure: What do you see as pro's and con's?

The free thinking environment is a great, but we're really getting away from "secrets of the Mod-50". Perhaps it makes sense to start a thread for developmental concepts and engines.

Sam - can...

The "axial flow" arrangement you discuss is called "uni-flow" in engineering circles. The low row of ports is used in the Detroit Diesel two stroke and my "HKS" two stroke and are actually 360...

All above mods were completed and the turbo was tested briefly Saturday which proved the following:

1) It idles nicely; driveability is excellent.
2) On rough water during hard accelleration, the...

The reason to operate all four valves at once is to satisfy port-time-angle-area gas flow requirements. Using only two of four valves cuts port/exhaust area in half, greatly limiting engine power. ...

In the mid-late '80s I saw one of the 2-stroke Ford Escorts you discuss at the FORD-OCP plant in Techumseh, MI. Quite impressive, it absolutely fried rubber off the otherwise sedate little econobox....

You're quite right about RPM limitations. But you might be surprised: The 1990 Cosworth cylinder head used for HKS was rated to 13,800 RPM with conventional springs. Dividing by 2 gets you 6900 RPM...

Mr. Nerstrom,

Thank you for your kind comments regarding project Virgo - I'm pleased and honored - also for sharing historical information regarding OMC turbo projects. 1972 was very early in...

Sam's right on again. The idea for my "HKS" Cosworth-Johnson came directly from Loctite customer Detroit Diesel in 1977. I was amazed by those big two-stroke cylinders with a low row of intake...

http://www.boatracingfacts.com/forums/showthread.php?t=7707&page=10

Here's an exercise on your exhaust valve concept.......... scroll way down the page.

Tim

Regarding scavenging: Sam's answer is correct, the turbo restricts exhaust gas flow. I've given passing thought to installing a butterfly (and pressure guage) in the exhaust duct to test the effects...

Hi Jeff,

Thanks for asking. Yes, there's been progress:

1) The idle problem has been solved.
2) The front end was removed and reeds inspected - all perfect.
3) Reed stops will be...

The idle mystery has been solved. Indeed the idle bleed was inadvertantly blocked off (by me). This series of carb uses a slot in the carb flange gasket for feed - have never seen this design...

Spent a little time in the shop tonight on Virgo. Here's what transpired:

1) Removed plenum cover to find a pool of 2-stroke oil in the bottom (expected), but no evidence of debris - yea! A...

Sam's prediction is absolutely correct: Full boost is achieved by the time the prop grabs - gotta be very careful getting on plane.

Does anybody know the is the torque limit for the OMC 1/2"...

Ran the turbo again yesterday with a .089" (richer) main jet. Still uninstrumented except for boost and EGT, but seems to run even stronger. Had good water for only 10 min, but saw 11-1/2 psi boost...

http://www.youtube.com/watch?v=B5TYP-oEpnA

Here's more testing with more aggressive throttle. Enjoy!

Tim

http://www.youtube.com/watch?v=TjBEFedL41Y

OK everybody, I'm not happy with the quality on YouTube (my first upload), but here it is. The objective was to shake out the engine, so it only gets...

What a morning!

You'll have to wait for the YouTube videos - likely tomorrow. Life long friend and photograper Vic Banta shot high def video with excellent sound. Though the lake was a bit...

Hello all,

Thanks to all for your interest and enthusiasm. A chase boat is confirmed tomorrow morning early. The engine will spin a known 8" X 13"P 4-blade DeWald. Boost and turbine inlet...

Tonight's test wheel trials proved incredible! With 100LL avgas w/16:1 oil and water leaks solved, the beast pulled quickly to 10 psi boost with zero detonation. The auto enrichment system was...

Hello all,

Test wheel trials went better than exected today, except it was quickly learned I mis-fueled with regular laker mix - oops!. As a result, detonation started a about 3-5 PSI boost,...

Thanks to all for your interest, compliments, and wishes. At this point your guess is good as mine about sounds and performance. My greatest concern is keeping gears inside the case. Right behind...

1) The oil pump is a 12V-3A helical gear type needed to lube/cool the plain turbo bearing. It delivers 2.6 GPM and 40 psi and is available from RP Racing in CA.
2) This draw-through system using...

Hey everybody,

Here is "Virgo" after first fire late yesterday evening. It started easily on prime, and is much quieter than expected under no load. Test wheel work will happen next weekend. It...

Images of the completed engine soon..... Tim

Any dealer can look up the year by way of the model number - the serial number is not important. In general, you want the oval port block. Bridgeports are problematic due to heat...

Hi Al,

Ahhh, you know me too well! There's another trick engine (or two) up my sleeve for this summer. I hope to run one of them if schedules come together. It will be tough to beat my own...

Thanks Alan, Yes, many hours have been consumed in those two beasts (and they're not done yet). Images will follow with completed work.

Glad to hear you've got the 44XS up & running. Claimed...

Thanks for your thoughts Sam, The price of turbos has come down significantly, hence this experiment. I've designed it to "bolt on" to a stock 56 - there will be no internal mods except for Boyesen...

Thanks Sam. If all goes according to Hoyle, the fun will be in the trigger squeeze. If the beast proves stable, you're welcome to drive it at Hillsdale this fall - there's an open test day on...

Just in case you think engine building is all work and no play......... The mockup is complete; it's time to assemble the real thing.

OK boys, this thread has been quiet for too long, so time to cause some mayhem........ The 850ccH class will get livelier this summer. K3 is about to be unleashed!

Unfortunately, it won't fit under a cowl, and also needs free air cooling. It will be in the open for all to see - including the marine patrol unfortunately!

Hey Fred, I forgot to answer your question about the pop off valve:

One of the benefits of a draw through system is a pop off valve is not needed. With the carb in front of the turbo, there is no...

Can't say for sure if SeaWay has any loose fronts - you might call Dave Losvar. But, I've got a one angle 8-petal, one straight 8-petal, and two 10-petal crankcases. Some have manifolds/reed plates...