Fuel line problem

[Gill7858]

Hello everyone,
I have a 2002 ox66 2 stroke 250 hp. I recently changed out all my fuel lines from tank to engine, replaced the fuel filter on the engine, primer bulb, and fuel/water separator.

I realized after I was complete that the fuel hoses were all 3/8" except for the hose that goes from the primer bulb to the engine which was 5/16". Just took the boat out and everytime I throttled up the engine would shut down then kick in again on its own. I made sure the primer bulb arrow was facing the right was and nothing was disconnected.

Is it the 5/16" hose???

Thanks in advance

[Gill7858]

One more question, is the fuel filter cup that's located on the engine suppose to be filled all the way to the top and stay filled??

When I prime the bulb it fill it to the top and after running the engine for a little while, the fuel line drops to a little past half full.

[bajakeith]

fuel problem

its not the 5/16 hose but do change to 3/8..it could be the anti sipon valve on the tank,,plugged screen on tank pick-up,,bad lift pump (s) ,,VST filter plugged,, pressure reg. screen plugged..air leak and a host of things !!!! if you think that its in the tank and lines,, run a 6.6 tank straight to motor filter and test run...and have you tried having a buddy pumping the primer pump while running ??? K&T

[bajakeith]

Post script

DO NOT,,,DO NOT use a tempo or moeler brand for any fuel related part !!!

[Gill7858]

No I didn't have my buddy pump the primer bulb. The hose is now 3/8 but it was 5/16". I have to assume that it's something I did because the problem started immediate after I changed out the fuel lines and primer bulb.

Is there a step I missed? Is there a way to make sure there isn't any air in the lines? Also my friend told me that mercury primer balls are the best so I bought one, is it not compatible with Yamaha.

I noticed the engine shutting off the most when now would lift up due to a wave. Once the bow leveled off the engine would start up again. I don't know if that means anything but maybe you might.

[rodbolt17]

check for any airleaks, make sure the engine filter oring is there.
check/gut the check valve between the filter cup and the lift pumps.
check the lift pumps.
the 3.1l engines are hard on them.
check fuel rail pressure while its failing.
8mm(roughly 5/16ths) was the size of the factory fuel line.

[bajakeith]

primer bulbs

the new upgraded merc p/bulbs will have a yellow band at one end and for best results install 4" or 5"" from motor cowling with the arrow pointing up..as in towards the sky...makes um work much ,much better !!

[Gill7858]

I reinstalled the 5/16" hose, put back my old primer bulb and re tightened all the hose connections. Heading to the ramp now to sea test. I'll let you know how it goes!!

[Gill7858]

Okay so I took the boat out for a test. anytime I would throttle up it would lose rpm and I was not able to get on plane I bypassed the water fuel separator just for shits and goggles and nothing. I did however notice that every time that I if I disconnect the hose there's no pressure. Before, I would disconnect a fuel hose and fuel would rush out of the hose and squirt me eveywhere and now it doesn't do that so I know that there is no pressure in the hose. Is it just a bad fuel pump????

[99yam40]

quick connect line from tank to motor is being sucked on by pump rhile motor is running, so why would it have pressure? Use you head.
or are you disconnecting a hose after the pump?

[Gill7858]

My head? Brother I lost that a couple of steps back. I'm trying to just retrace everything I did and see what I messed up. I was told that the lines remain "pressurized" and that the filter cup on the engine is suppose to stay full without the level ever dropping. By far, I'm not a mechanic so I'm trying my best here.

I know the pumps suck in from the tank when it's running but thought (based off what I was told) that the lines are supposed to keep pressure. I'm guessing then its a bad fuel pump or clog in the tank pickup screen? Frustrated.

[rodbolt17]

ok, you were told wrong.
it happens.

now lets take an objective logical look at the fuel lift pumps.
their sole purpose is to suck fuel from the tank and place it in the vapor seperator.

as they are sucking devices they would rather move air than fuel.
remember,pumps are even lazier than me.

as most of the system,filters, is on the suction side, there is NO way the cups will remain full.
aint gonna happen.
in the words of the immortal cowardly lion, aint no way no how.

that vapor seperator will hold enough fuel for a couple minutes of WOT.

either you have a high pressure issue or the lift pumps cannot keep the VST full.

if you ever have pressure on the suction side,you have an issue.

[Gill7858]

Ok my mechanic just pulled my VST and the electrical pump filter was clogged. So that's taken care of. He's still diagnosing it because when throttling up it surges from 1700 rpms to 2300 rpms, up and down. Any ideas rodbolt? Btw thanks for the input.

[bajakeith]

VST screen/filter

I clean the U.S.C.G AUX VST filter every 100 hrs ( OX 66 250's) just so while they are doing SAR they don't need help out there !!!

[bajakeith]

Btw

there is a check valve next to the motor fuel filter that should be checked and all (3) lift pumps should be changed....they are cheap and do not like ethanol.....39 buck or so for each pump..just have them changed if you want a solid running motor...I do not understand what your saying is your problem ??? and for fuel system parts ONLY ,,ONLY use yammy,,merc,,sierra parts...nothing from worst marine for you fuel system....and btw the way I am embedded with WM.. as the owner lives 3 miles from me and the headquarters is based here...great place for boat shoes,,shirts,,sunglasses but not engine parts !!!!!!