OS FS30 marine conversion

Yes very hot here I am about 4-5 clicks from the sweet spot on top end rpm. I did a second run after this vid
leaned it up 2 more clicks it would clear it's throat and bolt on the straights after each turn. About 5 to 6 mph
faster with the same prop in the this last vid, that had it's best pass at 43mph so 48-49 ish mph. The wind picked
up and the rigger cartwheeled I had to fetch in my Kayak. I did record it but the file is bad it won't play for some reason.
Shows a file size of 2.3 GB

I would have loved to see what happen again. Coming off the straight away I turned into the wind / choppy water
and it did two hops then caught the right sponson inducing the cartwheel lucky for me it landed right side up.
Just needed to back off the throttle a bit in the bad area's.

I have two more props ready to go will try the left one first it may be all the prop I need maxing out the riggers
speed in typical water conditions at my club, to go faster the water will have to be flat calm. The NV will be put on the
sweat spot for max power then backed off just 2 clicks for the next test. The big monos can get up to the low 50's and
not flip if throttle management is used when the wind has the water choppy. I have seen a gas rigger make it to 67 mph
per my radar gun.  Glass smooth is rare at the time most of us show up to run but if willing early in the morning around
8am the conditions are perfect for about 2hrs.

Yes cut the run short at 4mins last time it ran I didn't get the chance to check temp ran it out of fuel rich managed around
51/2 mins. from start up. I think with the right NV setting it should do about 6.5 mins. running full throttle. I have a stainless
steel tank made for the rigger custom size there is room to fit a bigger tank but the guy charges 80 bucks a pop per tank. It
holds about 4.5oz could fit about 2.5oz in size.

Second pic shows the bare case of the engine I am not sure if you can fit a cooling ring due to the way the head bolts stick out.
I appreciate the offer Jim, if it was possible I would buy a bare case and mail it out your way.





Still want to build a big rigger for windy weather this one is 5ft. 1.5" in total length counting the back of the rudder. Perhaps I
can source a OS Surpass that can be converted to water cooling something like a 120 size. Shown with a Saito .72 and 31.5"
total drive line to the end of the stub shaft.

To fit a cooling jacket, the top five fins would be machined away to form a cylindrical surface. The engine is then "dry assembled" with the liner head and pushrod tubes in place and then you carefully measure the clearance between the pushrod tubes and the crankcase using number size twist drills as inexpensive shims. The water jacket is then machined to a slightly smaller outside diameter and shrink fit onto the crankcase. For my FS30 conversion, using this method, there is enough clearance between the pushrod tubes and the brass jacket to fit a sheet of paper; no more!
So you pretty well need the whole engine assembly to do the conversion properly. As to the diameter the fins are machined off to, I remove as much material as possible while still leaving the head bolt threads complete with maybe .2mm stock allowance.
Altogether a fun project for someone who likes metalworking.

BTW, I think you're pretty brave running these models without a retrieval boat. They have a way of quitting in the most inopportune locations.

I use a fishing pole with a yellow rubber practice casting weight, If need be I
use this Kayak "Intex K1 Challenger" here to fetch. It airs up fast ready to roll in about
10 mins once out of the bag. Thick mill vinyl very tough $89 bucks.

The air pump shoves big volumes of air in per cycle. I always bring it on reserve,
most days the club boat with outboard engine is there to use. 2 club members have
engines they bring they have pickup trucks with hitches the club boat stays up the top
of the road when not in use on a trailer.

Jim I am looking at the top bolts and the lugs stick out too on your OS .30 how did you get around them
to achieve good leak free water cooling? Seems like all the Surpasses are this way. Do you have any pics
of the case after it has been prepped for the ring?

On the FS30 there is very little room for a water passage. The upper fins are blocked once they have been machined up to the head bolts. The bottom fin is the only one with a complete passage around the block. And the area where the piston pin removal hole (not used on the FS30) was slotted open with a dremel. I needed to mill small passages under the water fittings to provide a passage to the lower fin region. Finally, the existing 2.5mm head bolts needed to be replaced with 20mm long ones so that the bottom of the tapped holes could be sealed. (If not, water would leak out of those)

The larger OS engines, 40 and up, have a piston pin removal hole lower down in the block meaning that a larger passage can be machined into the block for cooling with a lot less fuss than the FS30 required. There are photos here somewhere showing the machined block for an OS FS48 but I don't have any for the 30.

After running my Ski Daddle Too with the FS30, I think even the 20 or 26 four stroke would have adequate power to push the boat along nicely, but I couldn't figure out a way to modify the block because of the location of the piston pin removal hole (smack in the middle of the cooling fins).

There's another modeler on RC groups (Gkymaz or something like that) who has a partially completed FS30 mod that you might be able to find.

But the larger OS four strokes should be able to be modified for water cooling with a bit of effort.

For sure sounds like a challenge each time Jim. I think you would have no issues running the 20 and 26 without
cooling just a matter of getting them in the water soon as possible and moving, that and be content running them
at least 2 clicks off peak or with a robust oil %. Next batch of fuel I buy will be 5% castor and 20% synthetic 50% nitro
25% methanol.

I need to buy a bottle of castor and add some to the mix on hand just enough to aid in cooling with the existing
dominating % of synthetic should help keep the engine flushed avoiding build up. Nitro naturally helps cool the
engine a big plus.

Since you run at a lake perhaps a big water rigger like these Jap boats could get you a run in when the winds
have the water all choppy. They are so long they engine needs to be in the back to help balance them out.

Radar pass at 42 mph ABC S-20
Forgot to tighten the plug lol did a gps run with a Dynamite logger got 44mph with
a tight plug extra compression makes a difference.


Tested the high pitched Octura 2250 rough water day had to take it easy in the open and turns.
Would gun it along the shore line, two run efforts in this vid ends with a rough water flip.
Info so far: 12,744 rpm pass into the wind and hit 46 mph

Best it's done so far is 44 mph needs more testing, I have not gone out there in over a month now.





To help cure stability in the rough stuff I swapped out the carbon booms to for more stance:

Wow that thing really moves! You were pretty close to the shore a few times. I had my 30 out a couple of weeks ago. Changed to a longer throttle servo arm and now I can get it to idle down to a slow walk. Sounds like its barely ticking over but probably 2000-2500 rpm to be honest. I'm still amazed how long it runs on its 6 oz tank. Probably because I run it at part throttle a lot.
I had photos of the machined case but think they were lost when my iPhone got wet and had to be replaced. It's a lot more fiddly of a job on the 30 compared to the 40 and larger but it sure is nice to have functional water cooling with that little tell tale stream coming out of the transom
This one was done on a machining center and is shown nearly complete in this image.

Nice Jim,

I bid on a Magnum 30 the other day missed out on it was cheap like 44 bucks was at work lol.
I figured it would be worth modifying for water cooling and should perform with similar performance
as the OS version.  Yes run the shore line for the still shots from the vid later. The trouble is I would
have to get out in the early morning for the sun to be shining on the riggers side view when it passes.
Without good lighting the still frames can be a bit grainy. So the only thing to do is run it close enough
to avoid shadows.

Will be trying the two props with the red stars under them next.
Would like to hit 50+ if all goes well.





Here doing frame shots I am looking when the hull is touching the water and where.
The rolling water really beats the structure quite a bit.

I was going to post about lowering the idle rpm on my converted FS30.

But.... It looks like I already mentioned this!

Now that the boating season is over for 5 or so months, I just have to say how much fun this project was to do.

The sound of a puttering Four stroke has to be heard to be experienced.

Agreed Jim it has been a treat to see what is possible with the 4 stroke in a boat.
I never did get a chance to do more testing my season is about over too as the weather
is rather cold here 35F when I left the office tonight. It even started snowing lol for the
first time since 1985.

Shoot Brad i was ck,ing this and it a wonder you guys were not tring to put skies on those boats ,may need a bigger prop though No snow since 1985 that just sounds weird ? for me anyway? I guess i am even boring myself now ! !

The snow was quite unexpected and a big treat for me to see again, perhaps more snow this winter
the odds are better for sure. Of course the boating season is over for now but perhaps a nice sunny
day with fare winds I may see some more improvements in speed. 5 other props balanced sharpend
and ready to test.