outlaw29

I have a new stock 260 with a big bore carb in a WHH Manta Ray. It has about 4 tanks ran thru it. Motor was running fine and stong. All of the sudden, when i make a right hand turn, the motor goes rich. If i turn the boat back to the left, even slightly, it leans back out and stays on the pipe. Left hand turns are not a problem. It seem that if i lean the hull to the right at all, it goes way rich. I know its not the prop size or needle settings or a load problem. I have tried props from 270, 275, x472. Small needle changes don't change the condition. Any body have any ideas as to what the problem might be? Thanks for any help

Russ.

viperdude

consider the direction of the fuel lines, maybe the turning causes an excessive flow of fuel into the engine, sort of like why some airplanes cant go upside down, but reversed., also, try poping open the engine, rebuilding it, with new gaskets, and seals, if that doesnt fix the problem, return the boat, and get a new one.

Captain Ramius

A. once you "pop" open the engine you won't be able to return it.
B. are you running a wet pipe or water cooled flange or coupler?

Also you should consider this:
The comment regarding tank attitude only applies to nitro.
The nitro carb siphons fuel , and is aided by tank pressure
from exhaust presssurizing tank ,sometimes external pump. The tank attitude may increase head pressure and cause the rich condition stated above.
The Walbro carb with its pump is not affected by this and the
miniscule amount of head pressure from tilting boat would
not cause a rich condition unless there is dirt in the
inlet needle and seat.
Other possibilites are a tank vent that gets covered during a right hand turn and
A leaking o-ring on the exhaust could cause a problem if the pipe was
moving when the boat leaned to starboard or if it has water cooled flange
it could leak water into pipe and change its effective tuned length by lowering egt.And sometimes if aided by a pump flood pipe.

gdavis9999

I have the same issue with my WHH Magnum 57 that has a G260PUM engine with the M5 mod.

When doing tight right hand turns, the engine bogs down. Left turns and straight, it runs great.

What causes the bogging/loss of RPMs on the right turns?

glennb2006

Generally, load increase.

Glenn.

gdavis9999

Glenn, if it's a load increase, why is it happening only on the right hand turns? Thanks

jacob711

its to do with prop rotation, but the thing is only on left hand turns it should load up, right turns should be fine

i highly doubt that this problem is mixture related (rich)

martno1fan

Glenn id have thought theres more load on the prop in a left turn than a right due to the props rotation no ?.The props rotation usually makes the boat want to turn right so id have thought turning left causes more load than a right turn.

But my money is on what someone posted ,a water leak into the pipe when boat leans right maybe the water is entering the header and bogging it down as ive heard of this problem before so id check you dont have any leaks in your cooling system to the header or pipe as any water leaking into the pipe itself can run towards the motor if the boat leans a certain way and cause other problems as well as bogging down.It could also be the tank do you have a clunk in the tank maybe thats the problem ,it depends where the tank is i supose but if its to one side that could be the problem maybe?.
Mart

gdavis9999

I got feedback from Tony and this makes sense:

Due to torque roll, the boat wants to lean to the right. So when you make a tight right-hand turn, the boat leans more than a left-hand turn, and the wetted surface of the boat increases a lot as well. The boat can even spin out easily in a right-hand turn if pushed too hard. Also consider that in a tight turn, the torque roll effect itself is higher, due to the added force it takes to turn the boat. The right trim tab is also often lower to compensate for torque roll, and this father increases drag. All these forces result in increased load on the engine, and the RPMs drop. It has nothing to do with the engine running rich, fuel lines, centrifugal forces, etc (unless there is some issue with the engine or fuel lines). It's just more load on the engine.

Now, in a left-hand turn, the boat handles quite well because the same torque effect keeps the boat from leaning in too much and it rides more level. This decreases the wetted surface compared to the right hand turn. Further, the left trim tab is often not lowered much. All of this results in less drag in a left-hand turn and the engine does not bog down. The key to maintaining faster speeds through the turns is easy arcs and smooth steering, this will keep the RPMs at their highest.

The same effect is found on full-scale boats, but the effect is higher on model boat. this is because the RC props are much larger and the HP to weight is also greater if scaled, so the forces are greater.

glennb2006

If you have your tuned pipe set somewhat on the short side, it can cause the motor to "bog" a bit when it gets the additional load on in the turn, might be an idea to experiment with a slightly longer pipe, this of course is affected by prop., set up, engine settings and state of tune as well as boat trim!

Might be worth trying, depends how sever the issue is. As you said in your mail, longer turns should keep the speed up better, but invariably, it's a longer way round!

It's all about the best compromise.

Glenn

Edited typo.

martno1fan

Ive never noticed any higher load in a right turn than a left to be honest, if the boat bogs down in a turn due to load on the prop all i can think is your slowing down too much .
Mart