Nitro BOAT Problems

[HoDog16]

I have written once before about my boat problems but nothing has worked. The boat almost always dies out in the middle of the pond, the running time it has varies anywhere from 3 minutes to 15 minutes before it cuts out. Ive noticed that the primer on the fuel tank is wobbeling and might be letting air out. I think that there is just enough pressure in the tank to get the boat running but it stops running when there is not enough pressure (because of the air leak) to feed the fuel into the engine. I dont have too mutch experence with nitro components yet so this is my best guess. Does this sound like a reasonable explination? If so, should i just replace the fuel tank? Thanks

[TC3Racer]

where did fuel tank come from? i meant pretty much what gubbs 3 said. seal it up best ya can, and if that dont work buy what you need to to replace it.

[Gabe]

Tank pressure or a lack of doesn't kill engines...
the tank pressure causes diffrent things,
-tank under preasure is like fuel injection, the needles on the carb are closed down a bit to keep it in check... it isn't a perfect compairson though.
-tank not under preasure is more like a older real car... the air flow ***** fuel out of the jet in the carb. & fuel line

if you tune for a pressurized tank & THEN loose the preasure the mix LEANS out...

water cooling could be covering a problem...
engine too hot? (burntout or distorted glow plugs)
low mix too rich too lean?
idle too low?

how does it idle?
it smokes when it goes across the water?
accellerates smoothly?

[HoDog16]

the boat idels fine and the smoke is visible out of the exhaust. the water cooling is clearly visible. I thought that there was a leak between the engine and the header because i couldnt keep the header on. But now that it stays on the boat still cuts out.

[MaximumST'er]

:D Boats are my specialty. First, check out your glow plug, if your boat gets started and runs fine, then it's probably your plug or flywheel. If your flywheel is loose then your boat will run fine, but under certain condiditions it will cause your boat to stall. Don't ask why, it just does. Also, chekc your mixutre needles. Your low end could be causing your engine to flame out. If the engine runs fine, but doesn't idle well, and starts up sluggishly and runs good when it's hot, then it's too rich, and needs to be leaned. If it starts fine, but deteriorates in performance when it gets up to temp, then it's too lean, and needs to be richened. Also, replace your plug and get a good one. For 40-50% and up nitro, I used a McCoy MC9 or Enya 5. The OS A5 also works well. I don't think your problem lies in the fuel system, but just to be safe, cut out the primer and install a self tapping screw and a conical washer sealed with silicone in it's place.
If you still got problems, e mail me.
Nick

[Serius Black]

HoDog - Which boat are you running? If it's a Kyosho or Traxxas kit, I'd strongly recommend that you stay away from anything higher than 30% nitro. The engines included with thier boats were never meant to run at the power levels that you'll see with higher nitro content.
A weak link on most kit boats IS a leaky primer. It may not be the direct cause of the boat stalling, but it will make it nearly impossible to properly tune the engine. Since the tune of the engine changes as it heats up, the leaning effect of the air leak could cause the engine to overheat and stall. You can fix this problem by removing the primer and plugging the hole with the right size screw and a rubber o-ring similar to the ones you use in most r/c car shocks.
Also, make sure that there is no fuel spewing out from under the head. I recently had a warped sleeve that wouldn't allow the head to seal properly, and in addition to the obvious effects on compression, it gets fuel everywhere. I don't think this is what's going on with your boat, as I'm sure you'd have mentioned it.
Carb settings can be a little tough to find, since things change quite a bit once you get water flowing through the head. Don't neglect your low end needle. Try and get a good balance between the high and low end.
I doubt you've got a problem with the flywheel, but you might as well check to see that it's nice and tight. The weight of the flywheel basically prevents cylinder compression from stopping the crank, piston and rod in thier tracks. It also prevents the engine from spooling up to maximum rpms too quickly, which would eventually lead to an untimely death (of the engine, not you).
When is your engine cutting out? Is it when it's accelerating towards top speed? Or is is when you let off after acceleration? Does the engine load up quickly when you idle for a few seconds, causing the boat to start off very slowly, spewing a ton of smoke?

[jeepinator]

No, I guess probably not. Stop listenning to me ... this is clearly Serious Black and MaximumST'er territory. What you are experiencing matches what I have witnessed be the problem before, but if your motor is this new, I am clearly wrong.

[Serius Black]

A squirrel on meth! LOL!

I don't agree with the guys at your local shop about the fuel. Think about it: Your RS4 isn't being run at near wide open throttle all the time. You slow for corners, and it's rare that the car ever really tops out. In a boat, you can have the engine spinning at near maximum RPM's without even having the boat on plane. It's not smart to do, but there's very little load on the prop while it's cavitating, which allows the engine to spool up quickly. Once the prop bites, the boat accelerates quickly, and when it tops out you're pretty darn close to the engine's maximum potential.
I've been told by some boating experts to run a heli or airplane fuel with a high percentage of castor oil, not synthetic oil. They said that the synthetic has a tendency to break down quicker than castor, creating more friction, and you know where that leads. I had always thought it was the other way around, and I've always run full synthetic in my full size cars, but the rule changes when you go from 8,000 rpm to 30,000 rpm. Maybe Steve can elaborate on this subject.

[Andrew the RC man]

completely offtopic but hot dog, how quick are them nitro boats???? im looking into getting a little pond scimmer or some boat that can slide over shallow water......my uncles cabin has a pond with canadian geeze that i like to scare :)

[Serius Black]

Andrew - I know you didn't direct the question towards me, but I'll tell you what I know.
Nitro boats can be quick, the slower ones do around 15 to 18 mph, the fastest ones on the world are doing somewhere around 118 mph. You can pick up a ready-to-run Traxxas Nitro Vee for under $300, which, out of the box, will do around 22 mph. With a few mods, I've got mine running over 30 mph, which actually seems alot faster driving it, because it's a little unstable.
If you want to drop a few more bucks, you can easily get a boat that'll run over 40 mph, but chances are, you'll have some gluing and sanding to do.

[HoDog16]

Andrew-I basicly agree with Serious Black on the boat question. My boat goes around 25 mph right out of the box and its alot of fun (when its running). If i were you, i would go with the Traxxas Nitro Vee because of its Return To Shore system. I wish i had one of those on my boat. I would easily sacrifice some speed for a way to get the boat back to me.

[HoDog16]

Serious Black-Does that mean i should up the ammount of nitro in my fuel too? If so, by how mutch should i increase it?

[HoDog16]

Now that you mention it, the boat mostly dies once i let up after acceleration. I can hear it start to stall and i can sometimes save it by giving it more gas. I know, however that the carb is open enough to get enough gas because i have checked it several times. Maby it is my fuel. I run it on the same fuel as my nitro rs4( which the hobby guys at the shop said was ok to do). This fuel is 16% nitro. Is this too low. By the way, it is a Kyosho Nitro Viper GT and i bought it as a kit.

[jeepinator]

I say compression problem.
I like serious black's post as well. He is giving KILLER advice here.

But, I say piston/sleeve is your main issue (lack of compression).

If it runs like a squirrel on meth when wide open but has no low end power (or won't idle) after it is hot, you may very well need a new piston/sleeve.

[HoDog16]

the thing is, the engine is practicly new. ive driven the boat like 3 times. Could the compression really be gone already?

[Serius Black]

HoDog -

Upping the nitro content won't fix the problems you're having, but it will definately make the boat a bit faster.
I had a Nitro Viper GT a few years ago, and I thought I remember the manual stating that you should use 10% nitro. My personal opinion is that as long as you get an airplane or heli fuel with a higher oil content, you should be ok. Use common sense, though. I wouldn't go any higher than 30% nitro, it seems to deliver more than enough grunt.
Check out your connecting rod every once and a while, replace it if it has obvious signs of wear. I've seen more broken rods than worn pistons and sleeves due to high rpm's. I've got a full gallon of 30% through my engine, as does the friend that I race with, and both engines still show high compression. I've replaced my rod, my friend hasn't.

[gubbs3]

I think the problem may be the low end needle. The first picco I had always died in the Main just before the end of the race like you explain. Once I finally found out the secret to engine tuning the problem was that the low end needle was too lean. It may sound backwards because they say a lean low end will make it idle higher but when coming off of a full throttle run the lean mix doesn't give the engine enough fuel to stay running because the RPM is higher than the carb allows at its idle position.
Next time you run your boat, start it, run it about 100' away and then back to you. Let it idle there as long as it can and if it idle kind of unsteadily and it gains speed the longer it idles and then finally dies the low end it too lean. Also try running wide open for about 5 seconds straight and then quickly release the throttle, if it goes lower than the idle speed the low end it too lean. Hope this helps!

[blegris]

Since we're talking about boat speeds, how fast do you think a box stock ProBoat Nitro Fury would run on smooth water, running 20% fuel?

I'm thinking bout getting one of these and I was just wondering.

Mista H :cool:

[Serius Black]

Mr.H - I've seen the Nitro Fury run at a hobby fair, the rep said that the boat hits around 25 mph stock, which is pretty respectable. If you threw on a good tuned pipe and changed the prop, you could probably get that hull to run on the edge.
I remember Boat Modeler did a review of this boat, I'm not sure if they got the claimed speed out of it, though.

[blegris]

Thanx Serious

Mista H :cool:

[HoDog16]

GUBBS 3- That is what my problem sounds like. It has all of those symptons, but i dont think it has a low-end needle (unless i dont know what a low-end needle is, which is very possible considering I have only been into nitro for a year). Mabe you could explain what it looks like as opposed to other needles. Also, what is the secret to engine tuning. Thanks

[gubbs3]

Well, I lied. There is no secret to engine tuning. It just takes experience. The low end needle should be in the throttle arm that is adjusted with a flat blade screwdriver. If there isn't a low end adjustment there's nothing else you can do. Try turning it 1/8 turn counter clockwise.