G4Bama

Miss Vegas Duece - Stock Super Tiger engine - Grimracer 36 x 55 prop

Spent the morning running and tuning on my boat. Changed fuels (Bryon's 40%/10%)and having to retune. Ran a quart of fuel and tune up seems to be going the correct way. Boat speed is good and throttle inputs seem to be good.
As the laps clicked off I would make adjustments. The one adjustment that seemed to be tough to iron out was the RPMs picking up in the turn then going flat on the straight away. I started on the high speed needle at factory set (4 turns out). I finished with the HSN about 2 1/2 turns out. The low speed needle is set to pinch test with a slight rpm increase and engine stopped within 5 seconds. At these settings my throttle is responsive and rpms seems to be steady in the the turn and seems to be maintaining in the straight away.Two things I have noticed is that if 1)I make my turn and maintain a slight arch in the straight ( keeping a slight load on the rudder) the boat keeps speed and rpm's more constant 2) Half throttle input on controller is wide open on the boat, applying more throttle makes no improvement. So when this is all said and done, I pull the plug to find itblack in color with the coil being gray in color. It is a blue O'donnells cold plug. AmI headed inthe right direction with these settings or have I pushed too far?Am I exspecting too much from this engine?
Sorry for being long winded, just trying to provide as much information as possible.

misshydro

Sounds like to me your still lean. Plus you oil content is to low for boats. Boat need to be 16-18% oil in the fuels. Low oils in your fuels will be lean burn on your engine. I'm running O donalds blues in my boats with no proublems. Had a friend garage mixed me a ***** of one gallon of 40% with 16% oil and a gallon of 50% with 16% oil in it. My plugs are burnning wright. Your plugs should be nice and new looking. if coils is in ,your to rich,coil pulled out and distorted your lean.

siberianhusky

Oil content has nothing to do with weather an engine is lean or rich, that is all needle setting, an engine can be run lean on 10% oil or 20% oil! As a matter of fact if you go from 10% oil to 20% oil and don't adjust the needle you will be running lean. You are getting the same amount of air through the carb and the same amount of fluid through the needle but you have 10% less nitro and methanol, the oil doesn't burn much so you have 10% less burnables in the fuel with the same volume of air mixed with it. That is what a lean condition is, nothing to do with oil at all.
Make sure you are not stalling the throttle servo at the end of its travel, when the servo has opened the carb all the way the servo should stop moving at this point, hard on the electronics if the servo is trying to push against the stop. Use the end point adjustment on the radio or trims and different holes in the servo arm and throttle arm. My servo stops when the carb is wide open but I can still pull the trigger farther, I dialed down the epa so I have the proper range of movement from the servo.
Is the fuel pickup still in the fuel when the boat is in a turn? you could actually be starting to go lean at the end of the turn and it takes the straight away to pick back up again. I don't use a clunk on a piece of flexible fuel line in the tank, I bend a piece of 1/8 brass tubing so it sits in the back port corner of the fuel tank. So if you were in the boat facing the front the pickup is in the left back corner of the tank, this is the side fuel is forced to in a right hand turn.
10% oil is not enough for a boat engine, that is car fuel! I like a fuel that has some castor oil in the mix, better high temp protection for the odd lean run. Amax mixes his own fuel though and I don't believe he uses a high oil content, but he also knows exactly what kind of oil he is using. I run 18% oil 30% nitro. When I can get it my favorite fuel is Sig Champion, comes with 3% castor. Next year I might go the home mix route I can cut my fuel cost by 50% that way, Klotz nitro, methanol and Klotz techniplate oil with some benol castor oil added.
Look at the condition of the glow plug element, if it looks distorted you are running lean. Never seen plugs diststort from a rich run, but I guess it could happen, just not sure how because the temp will be lower due do the cooling effect of the unburned fuel.
My method is high speed needle first then adjust low speed to get a good transition to full throttle, I don't worry about low speed much as long as the engine idles till I launch it and doesn't load up I'm happy.
Never bother trying to read the glow plug colour, unless you can do a real plug chop any idleing or low speed running will give you a false reading on the plug colour.
I read plugs all the time from karts and my old mx bikes but have never really been able to apply that to nitro motors, I always go by element condition.
I think you may have fuel pick up issues from your descriptions of it bogging after the turn and smoothing out at the end of the straights.
Hope this helps.

G4Bama

Thanks for replies. I think that i need to clerify the throttle positioning issue.My servo does travel and open the carb wide open. The point I was trying to make is that from 1/2 to full throttle there is no increase or decrease in engine performance.
I also agree with adding castor to the fuel. I am picking some up Monday.
According to the book on my boat: If RPMSpick up in a turn, with no throttle input,this indicates that engine is rich. That is why I am sitting at 2 1/2 turns out on the HSN. By "out" I mean turns out from fully closed or screwed all the way down/in.
When I finished my runs this morning I could hold and maintain throttle setting and boat would hold constant speed and haul the mail the whole lap. The black glow plug is what throwed me a curve. I had tried a medium plug and they are toasted.

misshydro

it matters.. The less oil in it,the more quicker and hotter the motor will burn the nitro. plus your cutting down the wright amount of lubercation your motor needs.....I was using traxxas 33% nitro. found out it had 10% between running medum glow plugs plus low oil content caused my glow plugs to burn the same way his was. I did add SIG castor oil to bump up the low oil content. Now I run cold plugs and running boat fuels, like O Donalds 40% and garage mix. Now all my motor pistions and glow plugs are clean. ....The black glow plug is what throwed me a curve. I had tried a medium plug and they are toasted. I'd poped my plugs after two- three runs. .. Ok I forgot,What motor are you running.? like size and maker? This would help us out to find your proublems.

G4Bama

Its the Super Tiger .18 that comes with the boat.
The one thing I have not mentioned is engine temps. I do not have a meter, but I do not believe that I have reached an overheated running point. I am leaning towards the added castor in the fuel solving my issue.
I would really like to have the Bryons 55% boat fuel, but no suppliers in my area. They carry car fuels and really gouge the price for SPECIALorders....go figure.

misshydro

If thats car fuel with 10% oil in it.. I was told to add 2 oz of castor oil to one quart of traxxas 33% racing fuel. So if you got a qallon you need to add 4oz of castor oil to it. Had a old boat racer calcuate it out on how much I'd needed to add.

G4Bama

It should be: Ounces of fuel x Desired percent you want to raise oil content -Example: 64oz. x 4% = 2.56 ounces required to raise oil content 4%
I have been reading about using medical grade castor oil, any thoughts?

amax

It sounds like you might need to raise the Prop\Strut a little. Is your prop sharpened and balanced?
10% oil is a little lite unless your Racing. I use 12% oil with 80\20% syn\castor and 60% nitro ALL DAY LONG!!
Medical Grade Castor is a bit extreme, Klotz Benol Degummed Castor is what I use if I'm add castr oil to the synthetic I'm using at that time or I will just use [link=http://www.klotzlube.com/techsheet.asp?ID=44&submit2=View]Klotz Super Techniplate[/link] which has 20% Benol already mixed in.

I have better luck with McCoy Plugs over the O'Donnell plugs try a MC8(med) or MC9(cold)

The only time the Color test on the outer ring of the plug work is with a new plug that has only run a few laps WIDE OPEN. Reading the coil as SH said is more effective.

Ron Olson

My Feedback: (1)

When you say that the plug turned black, do you mean the body of it? I got one really hot one time from the engine being too lean and the whole plug turned black. It's a wonder that it ran! I'd also say that you're running lean if there isn't anything past half-throttle

G4Bama

I did raise the strut up, running at 1" below bottom. Maybe more?
Understand about the plug reading, this a plug which had been ran previously. It was black after an all out full tank run (7-8 min). Iwas loosing my water to the wind and wanted that last good run. The piston top is black also. I dont think the engine is hurt, just concerned and trying to understand and learn the hobby at the same time.
As for the prop, No its not sharpened or balanced. I opted to run it as is. A sharpened and balanced prop is in the works.

siberianhusky

4 oz oil in a gallon will raise the oil content by approx. 3% Easy to figure out a ratio and percentage.
I did not state an engine doesn't need proper lubrication, but lubrication as I did say has nothing to do what so ever with the air fuel ratio which is what determines a rich or lean condition. An engine that is lean on 10% oil will be even more lean on 20% oil, because there is 10% less nitro and methanol in the same volume of fuel coming through the jet, therefore you need smaller percentage of air to maintain a proper fuel/air ratio.
A gasoline engine needs about 15:1 air: gas for proper combustion, 1 pound gas = 15 pounds of air, if you mix 25% oil in with your gas and don't change the jetting now you are getting 3/4 pound of gas, 1/4 pound oil and 15 pounds air, you no longer have a proper 15:1 gas to air ratio, you need to increase the jet size to allow 1 1/4 pounds of fluid to flow to mix with the 15 pounds of air this gives you 1 pound of gas to burn with the air and 1/4 pound of oil for lubrication and cooling.
I can't remember the fuel/air ratio for a nitro methanol mix but the principle is the same. A lean condition is a situation where you do not have enough fuel to air, a rich mix is the opposite. Since oil does not (or shouldn't) burn it has no effect on the lean or rich condition of an engine.
More oil will help protect an engine from a lean run but will not prevent a lean run.
Oil does not help nitro burn, Nitro methane is basically an oxygenator in the fuel for the methanol in the application we use, 100% nitro actually doesn't burn all that well needs a crazy air/fuel ratio, look at how much nitro a dragster goes through in a run! Oil is there to lubricate not help combustion, the oil helps carry a some of the heat out of the engine but the majority of cooling comes from the boundary layer of fuel between the piston and head at TDC, specifically in the squish area, this is where most of the heat transfer to the head occurs. I could go on about squish clearances but thats not the point of these posts. A lot of heat also goes out the pipe as un burnt fuel.
I can't imagine how many mx, road race bikes and karts I would have blown up by now if I thought adding oil will cure a lean condition. All that does is carbon up the top of the piston and exhaust port! Because the engine is still lean and running hot! And you made it worse by dropping the amount of gas in the ratio! A properly jetted race bike with 50:1 oil will last longer and run far cooler than one running 20:1 that is lean. The exact same thing applies to these engines 10% oil with the needle set properly is going to last longer that 15-18% oil running lean. But because of the demands on the engine in a boat more oil is your friend. With a proper needle set up.

here is some info about nitro as a fuel or fuel additive and how it works,

As an engine fuel
In a minor application, nitromethane is used as a fuel in racing, particularly drag racing, as well as for rockets and model airplanes and commonly referred to in this context as "nitro". The oxygen content of nitromethane enables it to burn with much less atmospheric oxygen.
4CH3NO2 + 3O2 → 4CO2 + 6H2O + 2N2
14.7 lbs. of air is required to burn 1 pound of gasoline, but only 1.7 lb. of air for 1 lb. of nitromethane. Since an engine’s cylinder can only contain a limited amount of air on each stroke, 8.7 times more nitromethane than gasoline can be burned in one stroke. Nitromethane, however, has a lower energy density: Gasoline provides about 42–44 MJ/kg whereas nitromethane provides only 11.3 MJ/kg. This analysis indicates that nitromethane generates about 2.3 times the power of gasoline when combined with a given amount of oxygen.
Nitromethane can also be used as a monopropellant, i.e., a fuel that burns without added oxygen. The following equation describes this process:
4 CH3NO2 → 4 CO + 4 H2O + 2 H2 + 2 N2
Nitromethane has a laminar combustion velocity of approx. 0.5 m/s, somewhat higher than gasoline, thus making it suitable for high speed engines. It also has a somewhat higher flame temperature of about 2400 °C. The high heat of vaporization of 0.56 MJ/kg together with the high fuel flow provides significant cooling of the incoming charge (about twice that of methanol), resulting in reasonably low temperatures.
Nitromethane is usually used with rich air/fuel mixtures because it provides power even in the absence of atmospheric oxygen. When rich air/fuel mixtures are used, hydrogen and carbon monoxide are two of the combustion products. These gases often ignite, sometimes spectacularly, as the normally very rich mixtures of the still burning fuel exits the exhaust ports. Very rich mixtures are necessary to reduce the temperature of combustion chamber hot parts in order to control pre-ignition and subsequent detonation. Operational details depend on the particular mixture and engine characteristics.
A small amount of hydrazine blended in nitromethane can increase the power output even further. With nitromethane, hydrazine forms an explosive salt that is again a monopropellant. This unstable mixture poses a severe safety hazard, and is forbidden for use in model aircraft fuels.
In model aircraft and car glow fuel, the primary ingredient is generally methanol with some nitromethane (0% to 65%, but rarely over 30% since nitromethane is expensive compared to methanol) and 10–20% lubricants (usually castor oil and/or synthetic oil). Even moderate amounts of nitromethane tend to increase the power created by the engine (as the limiting factor is often the air intake), making the engine easier to tune (adjust for the proper air/fuel ratio).

G4Bama

Well Ron, not the whole plug turned black. The bottom ring and the top of the piston. The coil is still straightand a grey/white color.
As for the lean condition, I'm with you there but the only way to gain performance was to lean her up. My last run was a good one, the boats performance was equal around the whole lap. The 1/2 throttle thing is weird to say the least. Max engine output at 1/2 trigger with no gain has me scratching my head. My truck enginegains throughout the whole powerband al the way to full trigger.

amax

1" in from bottom of boat to bottom of strut is still a bit Deep, I don't run grim props but when I run the Octura Y535 which is pretty close to the same as that prop I run it between 5\8" to 3\4"in from bottom of the boat to the bottom of the strut, these are considered Surface Prop which means the tips of the prop are meant to Pierce the Surface of the water.

IMO the blackness on the plug and piston, and lack of throttle response past half throttle, are from the High Load put on the engine from running the strut To Deep and the UN-Finished Prop, if the prop is not sharp it's Beating it's way through the water instead of Cutting through the water.

Get the prop Sharp and Balanced and Strut Dialed in and you will think you have a different boat. Running the prop unbalanced will greatly shorten the life of your drive train.

Your truck has Gears to compensate for engine load and let it get up in to the higher RPM Range where a Boat is 1:1 it's not going to act exactly the same as a truck, it's more like sticking your truck in High Gear and leaving it there for all your driving conditions.

misshydro

Ok no one asked this question. is your motor fully broken in? how many tanks you ran threw that engine plus what boat is this on,is it a miss vegas duce?

amax

LOL,, Boat Engine and Prop are all in The Very First Sentence He typed[&:], number of tanks isn't but he seems to have a good grasp on what's needed so I'm ASSUMING he has broke the engine in to some extent.

G4Bama

amax: You are correct in your assumption. I have broken the engine in. I used Grimracer 50% before swapping to the Bryons 40% I am running now. It was not a fuel qaulity issue, the issue was having to wait on the brown truck to bring it LOL.
I measured the 1" from the bottom of the boat to the center of the strut. I follow what you are saying about loading the engine with the prop beingto deep. I was assuming that the3 bladed props are surface props, while the 2 blades are meant tobe ransubmerged. Atmy current settings, the boat seems to be setting good on plane. She is riding on the back1 - 11/2" ofthe sponsons and about the same on the transom. I did notice a little rock/roll from sponson to sponson towards the end of the straights, but nothing that made the boat where I couldnt drive it.
I have had to order new strut bearings. The one that came with the boat was not the best design. Instead of being machined, it had a ring soldered to the main body. Needless to say it didnt last long. Trying to make time at work to make a balancing jig, but until then where is a good place to buy B&S props?
Idid pull the head and cleaned it up. Isaw no damage. Everything appears to be on the surface. The one thing that I did notice is that one plug extends further out the bottom of the head, and one was flush. Two different makes of plugs, Ionly have 2 cold plugs. Here again, waiting on the brown truck LOL. I had read a thread where amax stated that he runs his flush with the bottom. I dont think this caused the black issue, but did find it interesting.

amax

The difference in long and short plugs is only about 2 threads, O'Donnell plugs tend to be about 1\2 thread longer than most but they normally come with an extra thick washer on them. When I make my heads I like to make the Plug Boss the right height to hold a McCoy plug with the tip just entering the combustion chamber where No Threads on the plug or the head are exposed, Fine Sharp edges get hot faster than the rest of the head and create Hot amber's in the chamber which causes Pre Ignition.

All the black stuff in your combustion chamber is just Unburnt Fuel and Oil, you haven't hurt anything. The High load the prop is putting on the engine prevents the engine from tuning up to full RPM's while the carb is still Wide Open and dumping the amount of fuel the engine Should be burning At Full RPM's so you are essentially running Rich, Richer fuel mixtures give More Torque where Lean Mixtures give Quicker revving and Higher RPM's If it can pull the load put on it,, It's a Balancing Act.

I may have missed it but I see no mention of Head Shims,,, How many do you have in, If any??

Your strut bushing wore out Prematurely due to the Unbalanced Prop. The Soldered on Ring is ONLY to prevent the bushing from sliding to far in to the stuffing tube and not supporting the stub shaft. That is what you will get from anybody, if your buying Machined Bushings then your spending to much money They All wear out it's still just brass, that's what their there for. I make my own bushings from brass tubing you can get at most hobby shops. I also Do Props If you need something shoot me a PM.

3 blade props do generally break the surface more than 2 blade surface props to unload the engine enough to get in the higher RPM's while still pushing enough water to get adequate propulsion. 3 blade props are often used for higher lift on the transom to obtain the true 3 point hydro stance a Sport Hydro Should have to achieve the best Handling and acceleration, Ideally a Sport Hydro(3 Point Hydro) rides on the 2 sponsons and the Prop with the transom just skimming across the surface of the water.. But the deeper a prop runs If the engine has enough power to turn it,the more efficient it is due to less slip from the Air that is pulled down from breaking the surface. You want to raise the strut Just Enough to unload the engine enough to reach max RPM's while limiting the amount of Slip,, Again It's a Balancing Act!!

If your trying to Make a Prop Balancer, a Magnetic Balancer is the best,,
Somthing Like This

G4Bama

amax
So with the strut depth being off, this may have me going too lean to compensate for the high torque load on the prop. I see your point and I can agree with that line of thinking. So, my best option may be to go back to starting point (4 turns out) and work with the strut depth first?
No damage to engine. Disassembled and cleaned. The engine came with 2 head shims. I thought about removing one to raise compression, but opted to leave it in for now.

I will shoot you a PMlater. I am interested in the props, 2 & 3 blades. Thats a nice balancing stand, did you make or buy it?

amax

Yep sounds like you have the concept, but no need to go back to step 1. Put a S&B prop on it and raise strut to 3\4" bottom of boat to bottom of strut. At the most I would richen it about 1\4 turn and run it a COUPLE laps and adjust from there. Check Head temp at the plug and read the glow plug, Head Temp should stay below 190*F and above 140*F, that is also controlled by Fuel Mixture, Rich will be Cold Lean will be Hot.

I have NEVER Touched one of the thunder tiger engines so I cant tell you for sure but you Should be able to remove Both Shims. Ideally you want the Head\Squish Clearance set around .004" to .008" most the brass shims are around .007", so if you have 2 shims in your clearance is around .018" or More[&:] and I'm Guessing your CR is down around 7:1 to 7.5:1. Raising the CR will give you the ability to turn bigger props. I would pull out At Least 1 shim. I build my Mod Go Engines with CR around 9.2:1 to 9.5:1.

That prop balancer is a Production unit bought by someone else it was the first pic I found in the thousands I have on my computer of a magnetic balancer, I use a Zero G balancer which is very similar. Both are just Earth magnets on each side and a steel 3\16" pin to hold the prop.

res3567

So Amax....you are recomending a 3 blade prop? Which brand and what kind ?

amax

I mainly Use Octura Props, I like a 3 blade prop for heat racing or windy days but will run a 2 blade on slick water to let the bow float a little more to give less surface area touch the water.
On a sport 18 hydro with a Strong engine and high nitro I like the X437\3 or the M440\2, ZippKits.com also sells a 440 which is basically a Asian copy of the M440 which works real well also.

G4Bama

amax: Went back andgot you some numbers on the head clearances -(1) Shims .009 x 2 ( 2)Head thickness (through the glow plug hole to bottom ofring/head) .216 ( 3)With head installed, going through glow plug hole to top of piston @ TDC .226 That would leave a gap of .010 between the bottom of the ring/head and the top of thepiston @ TDC with no shims installed.

As for the props, I am going with aOctura Y535 & M435/3. These seem to get the most reviews for the MVD. LaterI plan to go to a 3/16 strut setup so for now I am not going to go crazy buying props.

boatnut

  AMAX, The prop balancer you show is a Chinese built unit.
I bought one new off E-bay,Great unit great price.
It comes with all shaft sizes. Very accurate,I love it.


    Having this much fun must be illegal

amax

Man I would Definitely remove all shims if that is truly your clearance, but if your using the depth gage on a caliper to measure it's easy to have a variable of +\- .003. I have a little more sophisticated equipment to limit the variables. I'll have to take Pics of how I do it, It's much easier to explain and understand with pics then type.

to upgrade to 3\16" hubed props you simply need a new flex shaft that's Not stepped down to 1\8". Mike AKA Toyotatruckin makes some Real Nice flex cables shoot him a PM if you need one.

With the Stock engine those will be the best props to start with.

Another Question,,, Have you sanded the bottom of the sponsons or transom at all??