Running some marine engines: OS MAX-S 30 RC

getback wrote:COOL !! Sounds good and throttles well , it will make a good runner in the water . It appears the water was not flowing very well in the video ? but am sure you will get that worked out with the installation. Thanks for the fun !!  

Eric, as said above, the thermosyphon didn't work because the water level in the tank was not high enough. It's less complicated to let the water flow in and out of the engine by gravity during running. The diameter of the silicon tube and the brass fittings of the water jacket restrict the flow to give plenty of time before the bottle empties.

I'd like to find a coupler for this engine, universal joint or for a cable, but the thread is uncommon. I measured a pitch of 32 TPI and the diameter is about 5,6 mm or 7/32. I've read on the web that a .15 FP has such a thread. Is that so?

Edit: that's the thread. I found this data sheet on the OS site:

http://www.osengines.com/parts/engine-specs-discontinued.html

Thermosyphon would also work better if the water inlet of the engine were at a lower level than the outlet.

Interesting engine again, I am curious to see what kind of a boat project you have in mind

I also have been looking at a "local" for sale ad of a marine Enya Fuji 35 for a few months, contemplating if I should make an offer or not It must be quite old, as there is no R/C throttle on it.

KariFS wrote:Thermosyphon would also work better if the water inlet of the engine were at a lower level than the outlet.

Agreed. Being an antique stationary engine restorer, I can tell you that thermosyphon will only work if one water fitting is higher on the engine than the other. Some early cars and tractors didn't have water pumps and only relied on thermosyphoning to circulate the coolant. It's surprising how high a well set up thermosyphon cooling system will actually pump the heated water.

Running a "total loss" cooling system as suggested is not actually very good for an engine because it continuously introduces cold water into the water jacket, not allowing it to reach an efficient engine temperature. The thermosyphon sytem is self regulating- the hotter the water gets, the quicker it flows from the upper engine outlet, drawing cooler water into the lower inlet. As the engine cools, the flow slows, allowing it to heat up further.

KariFS wrote:Thermosyphon would also work better if the water inlet of the engine were at a lower level than the outlet.

Interesting engine again, I am curious to see what kind of a boat project you have in mind

I also have been looking at a "local" for sale ad of a marine Enya Fuji 35 for a few months, contemplating if I should make an offer or not It must be quite old, as there is no R/C throttle on it.

I wouldn't mind making the Remora. It reminds me of the Graupner Taifun. But that will not be for the near future. On the Fuji35, there wasn't an exhaust throttle?

The thermosyphon was just an idea. I thought by positioning the inlet water tube lower than the engine that this would help. I just let the water flow through now for easiness. That's how it's done on model boats as well.

now thats a cool looking boat also by Vic Sneed .

Eric, I think it is too. When on the water, it seems to cut the waves well, even when the surface is a bit rough. But before building, I need to find a coupling first.

This video is on Youtube: a Remora powered by a slightly more powerful 28 MDS engine.


https://www.youtube.com/watch?v=ZuuemMGvRmw&t=172s

What engine is in the cruiser? Sounds like a 4 stroke.

706jim wrote:What engine is in the cruiser? Sounds like a 4 stroke.

The Sea Queen is powered by an OS 61 FS.

https://www.youtube.com/watch?v=xTwiUs5Q7B4

I've found this conversation on "thermo-syphoning" to be very interesting. The engine does need to "heat-up" to operate efficiently. How could it be done, running on the water? The conventional way of feeding cooling-water to the engine is via a pick-up tube, positioned into the prop-wash.. but as mentioned; it feeds "cold water" to the head via a conventional water-jacket. Granted; it's not "pumped-in" at a high-volume.. but it's still cold-water being fed directly to the cylinder-head. Maybe a simple restrictor-fitting in the line (or an adjustable valve) would meter less cooling-water to the engine? Tube-coils have been tried; wrapped around the engine-cylinder.. but they're intrusive. Most of the heat is right up top.. at the head. That's where the control needs to be IMO. Maybe trying different-size coupling-tubes would produce favorable results?

Regarding Vic Sneed's "Remora" design.. I love that look. Dumas "had" a little 1/2A runabout-design called the "Half-Pint Cabin-Cruiser".. that I tried to buy in the mid 1990's.. but was discontinued.



I wanted that kit BAD... I was bummed-out that I couldn't buy it direct from anywhere. I already had the Dumas hardware-kit for the .049 glow-engine installation.




It's a tiny 18" length boat.. but would be a blast to run with a Cox .049 engine. Given today's feather-weight radio-gear... that little boat could be a lot of fun on a small pond.

The Half Pint is still on the Dumas site:

http://www.dumasproducts.com/product_info.php?cPath=136_58&products_id=353

I remember the Half Pint, guys use to make them speed boats nix the cabin section
and dress them up for race use, would speed them up pretty peppy for 1/2A.

Check out this IC cabin boat er has some motah..

OVERLORD wrote:
On the Fuji35, there wasn't an exhaust throttle?

Not sure... The muffler does seem to have some fittings fore and aft the mounting flange, otherwise it looks like just an ordinary muffler. Could be that this engine is a mix of parts.



I am going to skip this one anyway, a bit expensive at 37€.

OVERLORD wrote:The Half Pint is still on the Dumas site:

http://www.dumasproducts.com/product_info.php?cPath=136_58&products_id=353

Thanks Lieven! I wonder when it was re-introduced? I haven't kept up with the Dumas offerings in some years now. The price has more than doubled.. but I guess that's to be expected..

I think that a slight dome to the cabin-roof and a windshield-visor would dress it up a bit. If I bought the kit, I'd make templates of everything. That's always a good thing to do with any kit; for reproducing parts.. or scratch-building another complete model.

1/2A Nut wrote:I remember the Half Pint, guys use to make them speed boats nix the cabin section
and dress them up for race use, would speed them up pretty peppy for 1/2A.

Check out this IC cabin boat er has some motah..



   

Yup.. I'd say it has some "motah"!! Kinda' silly to have that engine in a scale cabin-cruiser... but it sure runs good. It's really stable at speed in the straights. As big as that pool was.. it was too small for it. A good size pond on a calm morning.. or evening; when the water is like "glass" would be nice!

I hope that we have more model-boat activity here on the forum. There's so many models that could be explored. You've contributed a lot Brad.. and I love your Cox-powered models!

Thank you Roddie I should be able to get some good vid of the new rigger soon
been windy and rainy here, the water moccasins have been running around
at the club 1 got caught up in the strut of a large gas mono the other weekend.
He was banged up but alive and managed to free himself up and swim away.

pic from the vid..

The next engine is an OS Max-S 30 RC. When I got it, the engine was equipped with a blue anodized muffler that was screwed on with bolts and further glued to seal the gaps. Dried castor oil was abundantly present between the fins.



According to the 1968 Graupner catalog, this engine was not sold as a marine engine. One had to buy a conversion kit with water cooled head, crankcase cooling flange , bolts and flywheel.




I started removing the muffler. This glue paste could be chipped off and for 1 bolt, I had to grind away the bolt head as the slot was gone.



I managed to find an extra conversion kit for this engine which might be useful in the future. To replace the non standard muffler, I found an original new OS 703 silencer.




The first run was accompanied with lots of vibrations due to the crankshaft end play. Also, the engine did not run without tension on the glow plug. I supposed the plug was too cold and I replaced it by a Enya nr4. I made a thrust washer to get rid of the end play but that need replacing by a more durable one. The engine runs well but fine tuning is still neede and it starts from the first pull.



The video:

https://www.youtube.com/watch?v=8Xws5otUono

Hi Lieven, Are there any wear-marks on the back-plate? I didn't see any indication of the crank drifting fore/aft while running/throttling. The engine seemed to run pretty smooth.. albeit "rich. I think that I see excess un-burnt fuel blowing out-of the muffler's pressure-line.

Apparently a plug-change helped stabilize the engine with glow-driver disconnected? What were you using to pump coolant to the head? A conventional coolant-loop I think will run hotter. I wonder about this for bench-running marine-engines. The pressure/volume at which cooling-water is pumped to the head.. would directly affect engine-performance and throttle-response.. IMO.

Great that the engine is starting easily. Any history on the engine; as it was set-up? That blue muffler/header may have increased performance for a certain application.

Your OS Max-.30 doesn't resemble my  .29 C/L aero-engine..  but yours is an RC variant... and I have very little info on my C/L version.



This engine may have been built in 1962.



See though.. this photo of my .29's castlng ID..



Looks very close to the era of your .30RC.

Thanks for posting the vid Lieven!  I'm intrigued by IC model-marine engines.

Roddie, glad you liked the video! You can see the axial play on 4:42 when the engine stops. I haven(t inspected the back plate yet but there is some wear on the back of the drive washer. The water is just flowing through the engine by gravity.



For dating OS engines, the OS website has a page. From the main page, choose "OS facts" at the bottom right and then click on "manufacturing timeline gallery " top left. Your .29 III is dated 1961.

http://www.osengines.com/history/ostimeline03.html

I never saw any year on the mounting pads of OS engines, only 2 letters.

I bought a OS Max .10F SR last year new old stock in box from a  
hobby store who was doing some liquidating of it's store stock that
was shelved in the back storage room.

I had seen one run in a Dumas Lil Rascal rigger back in the day and
was surprised just how much power the set up was providing on the
small rigger. For old times sake I may rekindle the moment with a
more modern rigger running tricks and a 1.5cc tuned pipe for sound
and make it run a: Lil Mo Peppy.

The design will have a taste of old school with sneaky speed tricks added
in without being too obvious giving a appearance of a vintage kit. At first
glance the guys at my club will think I have a old dog with no bite... just
a flashy new bark. Could do 45- 50 mph and be a fun non fussy runner.
Fyi...period steel chromed OS .10 flywheel.

That looks great. Is the tuned pipe the only mod? Do I see a nipple for a water cooled exhaust? I see no second nipple so I assume that the water is blown out by the exhaust. Great job!!

Thank you,
No mods to the engine other than adding a header and tuned pipe.
The tap on the header is for a pressure line to the fuel tank. Can't
run water inside the pipe the engine would get unwanted influx.

If I recall OS recommends running the cool water through the back
plate first then up to the head. I have the manual read it once.

My current boat project for the summer is a Saito .30 4 stroke
rigger here is the design layout. This weekend I finished one
of the sponsons thus far.

Hey Brad , whats the two nipples at the back of the CC for ? Is there a water pump in there ? I looked for a breakdown and couldn't find one . Nice looking OS !!