How do I use a test tank?

[pfoley]

Hi, I have a 2002 sx250. I think I may have bad fuel going into her. How would I hook up an remote gas tank to check it out? I know smaller outboards have a clip/plug at the engine that the remote tank plugs into, but I don't see that here.

Thanks

 

[flatsprowler]

Re: How do I use a test tank?

Just find where your line runs to your tank, from somewhere after the ball
just disconnect and reconnect to your external gas tank. repressurize and you should be good to go.

 

[rodbolt]

Re: How do I use a test tank?

if you suspect bad fuel and simply hook up a test tank your results will be the same.
first inspect the engine fuel filter,if the red ring is floating you have water in the fuel. second drain the VST into a clean container,it holds almost a quart.
inspect for debris.
if ANY debris is found its time to service the VST filter and the engine filter and the hull mounted water seperator.
yamaha reccomends a 10 micron with a minimum of 90 GPH when new.
at WOT the sx250 can blow fuel at 30 GPH without a problem
post what symptoms your having.

 

[pfoley]

Re: How do I use a test tank?

Well, one of the problems is that it can burn 30gph at WOT!! Okay, so I won't worry about that any more.

Previously, the engine was running rough (rough idle, cutting out at high speeds) so I took her in for service at a local Yamaha dealer. The dealer said she was dirty and cleaned everything out for $475. They also told me that the tank was dirty and needed to be cleaned before I ran it again. I had the dealer where I bought the boat clean the tank out (with dubious results as they are a dubious dealer), then I ran it again.

It did pretty well for a while. The day I winterized her she seemed to be running a little rough again and the rps were only showing 4600 rpms at WOT. It's possible, I later found out, that the trim tabs were all the way down, which may have contributed to the lower RPM. Anyway, I figured I had all winter to worry about it .

The engine only has 40 hours on her, and I want to take good care of her without spending another $475 to change the filters, etc. I bought the manual and have yet to study it completely. This motor is a little more complicated than the merc IL6 I used to work on!

Anyway, I want to learn how to service/clean all the filters myself (what's a VST?), and make sure the gas in the tank is pure. It sounds like your way is easier than mine so thanks for the advice.

The hull mounted filter I am familiar with (how do you check it?). The inline filter with a ring in it I am familiar with. I will see if it's floating. The VST I am unfamiliar with. I will look for it in the manual so I can check it for debris.

Thanks for your insight as always!

 

[rodbolt]

Re: How do I use a test tank?

ok
basic sensors on the SX250
O", measures the amount of oxygen in the exhaust, used to fine tune fuel delivery. if the signl to the ECU is faulty or missing fuel is fixed rich at low speed and lean above 4000, DO NOT run above 4000 or lean piston failure is likly.
map sensor, measures barometric pressure at key on then measures intake presure to monitor engine load, used to correct fuel.
crank position sensor,used by the ECU to determine crank angle and engine speed,Throttle position sensor,used by the ECU to determine throttle angle and the speed of throttle opening to adjust timng and fuel injection asychronus or synchronous modes.
Knock sensor,used to detect engine knock, will add fuel and decrease timing if knock is detected.
coolant temp sensor,used to detect engine temp for fuel correction mainly when warming up and once engine is warm,has nothing to do with over temp detection.
intake air sensor used to measure air temp. its also why this set up is referred to as a speed-density type EFI used to correct fuel for varying air temps(density).
if any sensor FAILS other than the O2 sensor the timing will be locked at 7* BTDC and idle will be about 1200 RPM. some failures will allow top speed others wont.
most isues are VST and lift pump related.
study your manual but look on the net for basic EFI and how and why it works. doesnt matter much if its in a car,truck boat or airplane, speed-density systems all tend to work the same.
fuel tanks can be tough to clean, make sure your hull mounted filter is 10 micron with a clean flow capacity of about 90 GPH.
once you have the engine back in the 5200-5600 RPM range I have had success with starbrite fuel system cleaner. but DO NOT use it until the engine is running well, by the time any system cleaner starts actually cleaning usually ya burned a piston due to lean fuel.

 

[pfoley]

Re: How do I use a test tank?

You're scaring me. I hope I didn't cook a piston. Could that happen in 10 minutes of running? What happens when it's cooked? Does it loose compression or sieze? Idle was about 700 - 800 rpms as always when I winterized her. Anyway, I will start reading the maunal.

Thanks again!

 

[rodbolt]

Re: How do I use a test tank?

10 minutes, normally not.
however as the 2 stroke EFI feeds oil into the VST then to the intake with the gas its possible, thats why I say try not to run WOT until its fixed.