Fast Fred's OMC Mod 50 secrets Thread #2

[Tim Kurcz]

I bet this doesn't go .... "eeeeeeee-oooonnnnNNNNN" when the prop catches and it gets on plane .... just "EEEEEEEEEE"

We will want video of that!


I predict that the turbo will spool completely up while the prop is slipping and the motor will be at full torque that the prop applies 100% when it catches

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 that is keeping pistons intact (hence EGT tuning). Finally, I don't intend to drive more than 100 MPH, just accelerate more quickly, and value my neck.

You'll all see results from test wheel work scheduled next weekend. If tuning proceeds nicely, the first driving test will be the weekend following. Photos will be posted, and video will be loaded to YouTube. Drivers impressions will accompany posts, of course!

To answer more questions: I haven't weighed it yet, but will post soon as completed. My guess is the entire engine (wet w/1Qt oil) will be 165-170 Lb. Not an engine for small boats. My 13' Ropp will handle the weight, but will be too small for the power if it delivers/ Here are basic specs:

OMC 56.6 loop triple: Bone stock, std bore
OMC CD-3 ignition system w/o rev limiter
Mod-50 flywheel
Garrett TB2509 small frame turbo
RP Racing helical gear pump & filtern
OMC 1-bbl carb w/1.437" venturi
Boyesen racing spec reeds

The tower, all ductwork, carb adapters, pelnum, linkage were built here. All are bolt on items. By the numbers, the TB2509 is capable of delivering 175 HP @ 8000 RPM @ 15 PSI boost. Boost should begin about 3000 RPM and peak by 6000. It will be limited to 5 psi to begin, gradually increasing with experience.

If the TB2509 proves too small, a slightly larger Garrett GT2252 capable of 225HP has been prepped if the mid range is too strong, or if more top end is desired. My target is 140-150 crankshaft HP in an effort to keep the engine and my neck intact.

Good friend and builder of the Merc44 turbo, Dixon Smith, suggests the biggest gain is from normally aspirated to 5 psi. After that, he says power development is fairly linear until metallurgy fails. We're both looking forward to the ride.

Keep the questions coming. All will be answered in due time.

Tim

[Tim Kurcz]

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, aggravated by water ingestion from the test wheel. All said, I poked the throttle enough to see 10PSI boost. Will go back to the lake this week with the correct fuel/oil mix, and enable the auto mixture enrichment system fueled with methanol-castor. If it spools up without detonation, the prop goes on! This thing has serious potential. I can't wait to feel the pull!!!

Tim

PS Equally shocking is the engine is surprisingly quiet!

[Tim Kurcz]

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 enabled and tested perfectly, but was too rich and disabled.

The engine pulled 6600 rpm+ on my 45SS test wheel. For reference, my record setting triple pulled the same wheel to 6200 an hour before Rich set the new mark.

So, this weekend it's off to the lake for a test drive. Will post images and results soon as possible. Stay tuned.

Tim

[Mark75H]

Video!!

[Sam La Banco]

Very, very cool, great project. EGT info would be interesting. Keep up the great work.

[Tim Kurcz]

Very, very cool, great project. EGT info would be interesting. Keep up the great work.

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 temperature (EGT) will be monitored: I'm not concerned with tach or speed. It will get a nice warm up on plane and get poked to 80+ a few times. I'm hoping the methanol injection keeps it cool enough to avoid a premature stick: There's no thermal coating on the domes yet.

The boat driver is a semi-pro photographer: Stills and video will be shot - the vid will be posted to YouTube. A link and stills will be posted to BRF sometime this weekend. Am neeeervouuuus about this one - many unknowns. Keep fingers crossed....

Tim

[Tim Kurcz]

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 rough, several 3-5 second WOT bursts were run. Acceleration was nothing short of spectacular. This and Dixon Smith's Merc powered dragboat are the best accel rides ever. Might get the chance to run them side by side later this year.

Technically, a total of 2-1/2 gallons 100LL avgas with 16:1 TCW3 and a half pint of methanol/castor was burned in about 15 minutes of run time. Plugs and piston domes show light coffee - a little lean - but no piston damage. Compression is 135 psi even - about 5 psi less than when assembled.

Without auto enrichment, TIT was 875-900F. With methanol/castor enrichment enabled, TIT dropped about 150F. Mind you, it was difficult to establish a reading quickly while watching the lake and accelerating like a bat out out of Hell (testing was on Half Moon Lake near Hell, MI). Boost in all tests stabilized at 11 psi. There was no turbo lag, and no perceptible difference in performance with or without enrichment.

The only problems were the engine still won't idle well (not a fishing motor anyway); richer jets will be installed in an attempt to improve. Also turbo oil burped from the reservoir vent hose. The level might be run lower and/or a small separator will be installed to capture future overflow.

A great day: Nothing broke and no Sheriff involved (for a change). Good thing we ran in the morning though. By the time afternoon arrived the launch was packed. A good half day is needed for jetting, tach, and GPS time to accelerate testing. I look forward to a less hectic test session and better water.

If you'd like to see it run, come to Hillsdale, MI Friday Sep 9 for a day of open testing with the Indiana Outboard Association. Racing is Saturday Sep 10 and Sunday Sep 11.

Enjoy the images for now, and let me know what you think after seeing the videos.

Tim

[850cc racer]

that is just awesome. cant wait for the video!!!

[Allen J. Lang]

Hi Tim, the MAD SCIENTIST is at work again. Looking forward to the videos.

[Tim Kurcz]

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 punched briefly a few times. You'll get a feel for it by the sound, roostertail, and explosive acceleration. Enjoy!

Tim

BTW: If you listen closely, you'll hear turbine whistle.