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Jun 20, 2019, 07:50 AM
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Help!

Nitro water cooling ?


There is so much to sort in this forum may be easier if I post a new thread about this topic.
I have a ready to run RC Nitro boat and have tested the motor yesterday.I only had 15% Omega fuel for my airplane motor but it fired up the old OPS .21 3.5cc boat motor in a few minutes.I bought the entire system for only 20 bucks and so far only replaced all battery packs and radio works 100%.
For cooling during test run,I connected small brass tubing out the rear of the boat where there was already a hole there.Made some simple fittings and hose,ran fresh water through the head and it flows nicely out the side port of the boat.I started the motor and it idled perfectly and the responce was a tad sluggish,but really crank the RPM`s...was incredible.Using 15% fuel I understand I may be better with 30% for better response.
My question here is where can I find methods to mount my water intake ? I have a hole in the rear of the boat high near the top to run hose or tubing,but where will it be best to mount the intake part? I see very little on this subject online and could use some tips and methods for this.
This boat looks and sounds really fast....can not wait to get it ready for actual run on a large pond or lake. FYI...rudder does not have a connection for water intake like I have seen on you tube.Most are electric motor examples.
Here is a photo of this boat,looks in solid condition even though not modern...cool anyhow.Note my home brew starter
Last edited by JimmyZ911; Jun 20, 2019 at 07:57 AM. Reason: Help
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Jun 20, 2019, 08:04 AM
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glgirvin's Avatar

water cooling


Hi Jimmie, There are a couple of ways to set up your pick up. If you do not want to put a hole in the bottom of the hull, you can drill a hole in one of the trim tabs and mount or solder a pick up tube with a angled cut toward the bow or you can use the nylon landing gear brackets and mount the tube on transom. Thank you, Gary
Jun 20, 2019, 08:59 AM
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Thread OP
That was a thought I had but not familiar with boats,was not sure if it would effect the trim action.I already have a hole in the rear of the hull and guessing was the original spot the builder put it.I see this method a guy used and sounds like what you are talking about...not crazy about being near the prop like that though. Basically...it does not have to be in the center of the hull at lowest point? Not sure how much of the rear will be submerged yet.
I know these are electric,but similar concept -
Better RC Boat Water Cooling (2 min 36 sec)
Jun 20, 2019, 06:53 PM
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Thread OP
So what and where do people buy fuel for these boats? My local hobby shop only sells 15%...runs pretty good in this engine but what is the proper SAFE fuel to run in it? I see a bunch online,but boat fuel is either way over priced or they will not ship the stuff to me in New York for some reason.I was looking at this one -
https://www.horizonhobby.com/AQUP2530?KPID=AQUP2530&CAWELAID=320011980001437634 &CAGPSPN=pla&CAAGID=63437903512&CATCI=aud-428582954839la-561597928958&gclid=CjwKCAjw3azoBRAXEiwA-_64Omnf9Ss24XqK0S3DCxbruiuxa-cYAdmPlJXQRryXNxLHeSN1jwSvaxoC2zEQAvD_BwE
But they do not ship to my area. And this one is criminal -
https://www.amainhobbies.com/aquacra...RoCsmcQAvD_BwE
Now looking to Torco...sent them an email for advice on fuel for this motor.
Jim
Jun 21, 2019, 09:00 AM
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glgirvin's Avatar

fuel


Hi Jimmy, I am glad that I don't run nitro motor anymore. When I first started racing in 1974, the standard race fuel was 40% nitro. As years went on i was told that any engine from the 40 size and larger does not need higher than 25% nitro. You spend more dollars than the increase you will achieve. The smaller engines ( .21 or less) like the higher nitro. I used 50% on my OPS 3.5 s and 25% on the larger engines. I have the same engine that you have. actually, I still have 2 used ones and 2 still new in the boxes. If you are not racing, I would suggest sticking to 25%. Thank you, Gary
Jun 21, 2019, 09:32 AM
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Gary,
Thank you so much for this info.I am somewhat familiar with these engines and know not to push them too hard.I am not competing with anyone,just want to have fun with this boat without breaking the bank.I was close to buying 30% and just received a reply from Technology Hobbies Inc. Who suggested 50%...but that is probably for those that run on the edge.I am not that guy and almost ready to use what I have...15% which ran in my opinion very good.The engine wound RPM`s beyond my imagination...almost frightening and observed some smoke from the exhaust...so it is rich burning,but not too much.Hate to torch the motor using higher nitro % not knowing much about tune up...maybe I am safer for now with what I have? Otherwise...25-30 will do fine for me. Looks like a fast boat so will need to decide where to run it.Lots of places here if no one yells at me.We own 2 ponds,,,will have to see if they are clear to test this weekend.Need the new starter to get here I ordered,so still going to be another week or 2 before I test her on water !!
Jun 22, 2019, 01:23 PM
RC boat Rock Star
John Otto is Technology fuels and he caters mostly to the racers. 40% or a little less is good for you. Avoid plane and car fuels as the oil content is too low.
If you're getting some lag when you blip the throttle, that's good. It means it's just a little rich but the load of the water on the prop will lean it out.
Jun 23, 2019, 10:50 AM
GloBroz PowerLab
1QwkSport2.5r's Avatar
Quote:
Originally Posted by Ron Olson
John Otto is Technology fuels and he caters mostly to the racers. 40% or a little less is good for you. Avoid plane and car fuels as the oil content is too low.
If you're getting some lag when you blip the throttle, that's good. It means it's just a little rich but the load of the water on the prop will lean it out.
Most airplane fuels are 17-20% oil which is more than adequate for marine engines. I’d suggest staying away from the fuels with full synthetic oils however. Car fuels are indeed lower - 8-16% being the low/high contents ive seen.
Jun 24, 2019, 07:10 AM
Registered User
Thread OP
Fuel I have now is Omega 15%...specs -
FEATURES: OMEGA is for use in all conventional glow engines.
30% degummed and fortified castor oil, 70% ultra-high viscosity
synthetic lubricant
17% total lubricant content
99.7% pure Nitromethane
Minimum purity 99.97% exceeds industry standard
Jun 27, 2019, 09:21 PM
Registered User
Thread OP
So I decided to pull the engine out an buy new bearings for this OPS. Anyone know where I can get crank cover bolts and gasket? Also,is there an easier way to pull the bearings without buying a 100 dollar tool?
Jim
Jun 28, 2019, 06:49 AM
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Thread OP
Now to see if this actually is as easy as he makes it look -
https://youtu.be/WhpwsjYoxM0?t=3
Jun 28, 2019, 10:54 AM
RC boat Rock Star
Heat the case in an oven at around 350 degrees and they should fall out.
Jun 28, 2019, 11:15 AM
Registered User
Thread OP
I will try this and been notified by others this is a good method.Thank you for reply.
I am still looking for crank cover bolts and gasket for this engine.
Did not see a gasket for the head but maybe need that too ?
Where could these be found?
JiM
Jun 29, 2019, 07:29 AM
Registered User
glgirvin's Avatar
Hi Jimmy, If you have the new bearings, put the large bearing on the crankshaft and ready to go. while block is still hot( after removing old bearings, install the new bearings before ir cools down. Thank you, Gary
Jun 29, 2019, 08:22 AM
Registered User
Thread OP
Gary,
Thank you for tips.
Will post results once all materials arrive to assemble this engine.I have been told that my connecting rod is bad and needs replacement.I have manual for this engine from Mantua website and appears to be OPS .21 3.5cc SLA type.In the manual it shows a bushed rod as part# 352...I found a #3524 online as NOS and went and purchased it.Once it arrives,will install and see if all is well using this FIRST. Getting mixed info on which is THE proper rod for this engine plus they seem hard to locate.Mantua replied and told me this about the rod I ordered - 3524 is a later version stronger conrod with 2 bushes. There can be clearance issues with the inside of the crankcase on engines made pre1998 as later ones were machined with more clearance.


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