I will never break in an engine in a boat again!

[El Zorro]

The 9X6 prop you are using is WAY too much prop for this engine. It is more suited for a .29 or a.35 engine. Most ,21 engines develop their peak HP anywhere from 34K to 38K RPM. I have built .21 engines for gas cars that turn over 40K and stay together. By running an engine "on the bench" to break it in you have the advantage of turning lots of RPM's ( within the engine's limits, of course ) but also controlling the heat of the engine with the needle valve ( fuel flow ). You need to prop your engine to peak out in the low to mid 30's RPM. An engine with an ABC piston and cylinder doesn't need a lot of break-in anyway. Most people run them way too cool in the boats and that is what wears them out prematurely. Something to think about...........

Dick Tyndall

 

[RonShaw]

You can order your engines already run in from novarossi

BINGO!!!....

 

[Glenn Quarles]

Please be REALLY REALLY careful with this kind of break in!!!! Yes it is a great way to do it, but is crazy dangerous if not done right! First the prop has to be mounted really secure with zero run out and zero vibration, and then you have to make sure the prop you choose will not come apart at very high rpm! I watched Nova break in an engine at the factory and they pointed out a hole in the ceiling where a prop blade went through it...they now have a heavy duty steel shield around the prop. They also used a much bigger prop trimmed way down. It was something like a 10/6 trimmed down to about 4" or 5" dia. This way you get the nice heavy hub and thick blades to help hold it together.

Even though this method works well, I would NOT recommend it to anyone unless they were very experienced with running VERY high rpm airplane motors! A properly done "normal" boat break in with a few runs out of the water and then running on the water will result in just as good final motor and has much less chance of going really bad.

GQ

 

[JoeWScott]

What needle valve do you have there?

Joe

 

[eekern]

It is the needle that comes with the .21dd.

I do appreciate your safety concerns. I always stand well behind the engine and have no one else around. Getting zero run out and no wobble is why I put the nuts the whole length of the threaded rod, tight up against the collet. Spins very true. I do like the idea of the larger, cut down prop.

I may revisit the hudy bench mentioned earlier, I'm sure I could fab up an adapter for a threaded crank easy enough. It has a very high pitch, small diameter prop that spins in a cage.

 

[Blackout]

If one is going to build a break-in bench for marine engines what about having the air prop spin between two pillow block bearings and then connect to the engine with the flex shaft? No worries of prop balancing issues and everything can be shrouded easier.

Thanks for sharing Eric!

 

[David Bryant]

A properly done "normal" boat break in with a few runs out of the water and then running on the water will result in just as good final motor

you're saying: just run the engine (rich), mounted in the completed boat, a few times (say 2 tank fulls), then running in-water (say 2 tank fulls)?

 

[Samuel Hagan JR]

A properly done "normal" boat break in with a few runs out of the water and then running on the water will result in just as good final motor

you're saying: just run the engine (rich), mounted in the completed boat, a few times (say 2 tank fulls), then running in-water (say 2 tank fulls)?

Yes. Extremely rich.

 

[Blackout]

Use a rich mixture to cool the engine, not water. A little water might be needed depending on engine, boat, and water and air temps. Hot enough where you can't leave your fingers on the head for more than 1-2 seconds.

 

[Ken Webb]

Pretty good breakin idea,but how would you do it with a front exhaust marine eng.? Use to break engs. in with the prop method back in the day before we had true marine engs. I'm going to breakin w/eng. in boat on my boat stand. Good idea tho, with the stand.

 

[moparbarn]

Use a rich mixture to cool the engine, not water. A little water might be needed depending on engine, boat, and water and air temps. Hot enough where you can't leave your fingers on the head for more than 1-2 seconds.

this is a very subjective method of checking temps. depending on what you do for a living, thickness/toughness of skin & tolerance to pain, the time you can hold a head button may vary (A LOT ). i'm an auto tech for a living & i can prolly keep my hand on a hot engine longer than most folks that don't work with their hands....the best way to get an idea of how hot 200* is, is to run your car down the highway for 10-15 miles, jump out & lay your hand on the radiator . most modern cars & trucks run at 195*, so that will be just about right. a better & more accurate way is to get an inexpensive infrared temp gun & check the temp down in the well around the glow plug, trying to shoot the actual head button, between the plug & the water jacket. i personally run the engine at a high idle & use the needle to regulate the temp. do that for 2 tanks, then 2 more, ocassionaly slowly squeezing the throttle to about 1/2 way to clear it out. then to the pond, just rich enough to keep it off the pipe, varying speed for 2 more tanks. then, drive it like you stole it. works for me, get an excellent seal that lasts for a few seasons, with proper care.

 

[eekern]

The same way except use a straight exhaust header.....

 

[dion smith]

Would hate to be around a prop explosion after seeing a bit of ally I was drilling let go from the vise. Hit me twice and did a full lap of my shed lol. My boats, car and I were very lucky this time

 

[Kevin Krogness]

Would hate to be around a prop explosion after seeing a bit of ally I was drilling let go from the vise. Hit me twice and did a full lap of my shed lol. My boats, car and I were very lucky this time

Reminds me of shop class! We used to launch anything we could find off the vertical wheel Sanders of course we didn't know any better at the time!!!

 

[Brad Christy]

Guys,

I do my break-ins in the boat, as well. I set the needle rich enough it will not get on the pipe at WOT, even completely unloaded. I run a tank through it just running a fast idle, WOT, rich-as-hell needle. Then I run a couple tanks through it, occasionally pinching the needle to clear its throat and scream its guts out (very short bursts). This is when you need to monitor your head temp. When it gets up to operating temps, shut it off and let it cool. Then I prop way down, remove the water line from the rudder, leave it way rich and run it in the water, rich down the back stretch, leaning it down a bit for the front stretch. After a couple tanks through it this way, I put a forgiving race prop on, reattach the water supply and start leaning it down a bit, but still using the lean/rich, front stretch/back stretch rhythm. It usually takes about a half gallon to a gallon of fuel through one of my 21s to get it properly broken in and ready for a full race prop, race day needle and WOT on the water.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

Model Machine And Precision LLC

 

[eekern]

Totally agree with the heat gun, I use one every time when the engine is ice cold. Just think of the stress on the piston and rod when cranking over a new cold motor.....

 

[RonShaw]

On NR engines, take Greg's advice. Save yourself a lot of time and fuel. For around $50, Glenn can order your NR pre-run from the factory. It will be very close to being ready to go right out of the box!!!....

 

[Tim_Duggan]

I use the heat gun trick also, then do what Brad Christy listed above. Only thing I would add is to let it cool at BDC.

 

[Blackout]

I had to use a heat gun on a real tight O.S. piston and sleeve that I had installed in my outboard. It was tighter than any of my NR engines were. Heated the head with the heat gun and it loosened up enough to turn over easier.

 

[julianconde]

Personally I prefer to break the engines in a boat. Yes it might save you time. But if you plan in advance you can break in your engines in one day or spread it out to 2 days.

I broke in 3 CMB 101 RS engines in 3 hours and 200 plus laps 6 gallons later on my a Roadrunner Twin and F Mono in 2013 Atlanta Springnats many people thought I was crazy to break engines in 1 day before the race but it's possible.

It's no fun to break in engines on a stand. I love running boats so to me is better to do it on the boat plus you can practice mill times and your starts as well.

Julian