Vapor lock solution in F225 03

[TownsendsFJR1300]

Hi Bob/All- having trouble identifying the part number for the VST relief valve that solved your fuel issue. I have an ‘04 F225 TXRC that is dying at idle and I suspect this may be the issue you had. I have inspected lines, the bulb, the filters leading up to the VST.

any help with this part number?

I'm guessing part #25:

ORIFICE, AIR VENT

: https://www.boats.net/catalog/yamaha...jection-pump-1



Capture.JPG

[Doggydog]

Sorry, you’re right. I don’t think it’s a hot start issue like what’s listed above. At the start of a boating day my boat will typically run with no issues. However, more recently, I’ll start the boat and let it idle while preparing to leave the dock. Sometimes in this 2-3 minute period the motor will die. To restart the motor I have to prime the bulb. At that point the motor will restart and seems to run fine for a few minutes (maybe less sometimes) and then dies again. I’ve inspected the lines from the tank to the motor and don’t see any issues. Underway there have been no issues with fuel cut outs. Not sure what the best order in trouble shooting would be..

[fairdeal]

I'll start the boat and let it idle while preparing to leave the dock. Sometimes in this 2-3 minute period the motor will die. To restart the motor I have to prime the bulb. At the point the motor will restart and seems to run fine for a few minutes (maybe less sometimes) and then dies again...

OK, so that sounds like the low pressure portion of the fuel system
is not keeping the VST full.
A common problem -
but with a laundry list of possible causes.

[Doggydog]

Would a good first step be to check if there is fuel in the VST right after the motor dies? I assume If the motor runs fine under power that the low pressure pump must be working fine? Or is it possible that at idle it doesn’t function properly and under power it would?

[fairdeal]

An interesting idiosyncrasy of that engine,
below 1200 rpms, the electric 'lift' pump -
the one that pulls fuel from the boat tank to fill the VST -
only runs part-time:
10 seconds on, 20 seconds off.

So yes, there have been cases where the engine runs fine above 1200,
but 'runs out of gas' at idle;
some defect, such as an air leak,
'handicaps' the lift pump performance;
its able to overcome the handicap when running constantly,
but falls behind when running part-time.

yes-the primer bulb can be a useful diagnostic tool,
how much / how little fuel the VST takes after the engine dies

in addition, it may tell you more,
if you have someone available to constantly squeeze it while running;
if the engine runs great as long as the bulb keeps the VST full,
that confirms the problem is 'before' the VST.

if the bulb itself has trouble pulling fuel,
that tells you what direction to look.

[Doggydog]

Thanks for the info. Pumping the bulb as the engine is starting to show signs of stalling (running a bit off/rough) does seem to help. It is at least good enough to give me time to give the motor some throttle to keep it running. However more recently the motor will stall not just at idle, but as I start to accelerate after having idled for a good while. From all the forum posts and research I’ve been through this is indicative of an empty VST.. I guess either from the relief valve that’s between the VST and intake or from a faulty low pressure fuel pump? Does this seem like the right direction to be looking in?

[99yam40]

I would think so.
but when this problem happens, you might want to shut off the motor and measure the fuel left in the VST

[Doggydog]

Got it. I assume draining it is the easiest way to measure? I don’t have a new gasket for it atm..

[fairdeal]

Unlike some other models,
the VST on the OP's 2003 F225
is NOT designed with a handy drain hose
and an easily-opened drain valve.

There is a drain plug -
but getting at it requires removal of the airbox.
Worse,
while draining, the contents are not able to be fully captured.

Personally,
I would make my evaluation of 'how full is the VST"
using the primer bulb:
with some practice / familiarity
the number of 'squeezes' required is an excellent indicator.

[Doggydog]

I appreciate the responses! Thank you.

It was a bit awkward but I didn’t make a mess..

Today I replaced the fuel water separator, inspected lines, cleaned that orange cup filter screen, and then put everything back together - got out into the water - and ran the motor at idle until it stalled. Took about 10 minutes to stall. I was simply at the dock idling. Not driving around heating up the motor beforehand.

After stalling I got a cup contraption setup to catch fuel leaking from the VST drain plug - but unsurprisingly the VST had practically no fuel in it.

So, new a new filter and screen cleaning didn’t help anything. No lines appear to be leaking air. And the VST is in fact empty after an engine stall.

Should I be calling a mechanic at this point? I’m capable of removing any of the components on the motor and replacing them- but I certainly don’t want to play the guessing **** and end up spending more than I need to. However, if I were to play the guessing ****- I’d guess:

69J-14989-00-00

69J-24460-00-00

[marchmadness]

pump the primer ball and fill the vst. Start the motor and look listen and feel. Is the lift pump cyling on and off? You can put your hand on the hoses and feel fuel passing through. Look at the filter cup when the pump is running is the level changing? Did you check the pressure relief valve. Its a one way valve that opens around 10psi. you can buy an after market lift pump for around 100 dollars, use it as less expensive test. yes parts are expensive but book time with a mechanic adds up fast. Look at new parts as part of maintenance.

[99yam40]

if the pressure relief valve does not close off as it should it could let too much fuel recirculate and not fill the VST at idle.
lift pump does not run long and cycles at idle

[Doggydog]

Thanks again for the continued help.

The LP fuel pump does cycle on and off at the intervals mentioned on this forum. At least by sound it appears to be working properly at idle.

I had cleaned out the filter cup and noticed when priming the bulb after the initial stall - the cup filled up. I did not pay attention to what was happening in the cup as the LP fuel pump cycled on and off. What should I be seeing in that cup during idle?

I took off the in line pressure relief valve (69J-14989-00-00) and didn’t notice anything in particular. I wasn’t able to blow air through either side. Not sure if I should be able to? I sprayed some cleaner in it but obviously that didn’t fix anything..

[99yam40]

you will need to find out for sure, but I believe it is set at 10 PSI like written earlier.
so anything above that should open it up
if it checks out good then look for an air leak like fairdeal mentioned
Sucking some air and some fuel

[fairdeal]

I took off the in line pressure relief valve (69J-14989-00-00) and didn’t notice anything in particular. I wasn’t able to blow air through either side. Not sure if I should be able to? I

The lift pump pressure relief valve is the 69J-24460-00-00
It should not open fully until >10 psi
of course it is designed to work with liquid
here it is being tested with compressed air:

https://vimeo.com/427057125