Learn me some F225 VST venting and what not

[oldmako69]

OK Maggots (and I say that with all due respect Sirs), here's the latest POOP...

[twins, both have just had the injectors serviced, new T-stats installed, new anodes installed, new racor filters installed, all fuel feed lines and clamps checked and rechecked ad nauseam, etc etc to fix my VST no fill and engine stall after prolonged idle, new lift and high psi pump installed on PORT engine, whatthehellamiforgetting......here ya go...

http://www.yamahaoutboardparts.com/f...t-th28017.html THAT PROBLEM APPEARS FIXED. AXE ME IN JUNE.

After replacing the lift pump on the OTHER engine, I took the old gal out for a spin today. Here's what I found.

Instant start, smooth idle.
Rapid throttle response.
Engines ran GREAT up to 4000. Sat there for a spell.
Pegged the throttles and got 5700 out of the Port engine and 5500 out of the Stbd. Now, bear in mind that the available run is only a mile or so, perhaps two, so I had little time to mess with motor trim and tabs.
I came down off plane for traffic and then jammed them down to the stops a second time. The STBD engine gave me a bit of scheise but wound back up to 5500. The PORT went back to 5700. I hit the no wake zone and slowed.
The STBD engine bucked and spat a fair amount. Then it stumbled badly. Then it quit. Then I smelled fuel.

I tilted that mother up, and limped back home like the sore loser that I apparently am when it comes to wrenching on these engines.

Back at the dock I pulled the flywheel cover and intake plenum. There was a fair amount of fuel in the motor splash well that had dripped out of the STBD engine when I tilted it up.

The VST "breather" hoses are filling with fuel. That fuel is being delivered to the hose which leads to top of the intake plenum. That fuel is excessive and is corrupting the intake mixture, and leaking out the bottom of the plenum.

WHY am I getting this condition? I did the exact same work to two engines. One is happy as hell. The other is in full Groucho mode.

Learn me about this damn VST venting. Please. Why am I getting excess fuel to the VST? OR, is the amount normal and its just not being properly vented / directed BACK to the VST? After all, it has two nipples and hoses on its lid. My guess is that "one is for comin' and one is for goin'". Just like the old "What's the difference between a rubber and a coffin" joke.

Did I mention that the damn things wound right up initially and I had a big grin on my old grizzled mug?

[oldmako69]

Au contrair my Bahamian Homie,

I believe that I have an over-rich condition which is flooding my VST venting and dumping excess fuel into the crankcase breather / VST fuel return system. That excess fuel is being forced up and into the intake plenum through the VST (return and venting ?) tubing. Sorry for the lousy nomenclature.

No fuel lines (anywhere on the engine supply - to the first stage filter, to the low psi pump, to the VST, from the VST to either bank of injectors) are leaking. Nor are the cooling manifolds leaking

The excess fuel is being shunted to the intake through the breather. My question remains, why is this thing puking fuel into the intake?

But I will surely fill a 5 gallon bucket just in case. I'll put it next to my extinguishers so I am ready to go, no matter the source of the combustion.

[fairdeal]

The VST "breather" hoses are filling with fuel. That fuel is being delivered to the hose which leads to top of the intake plenum. That fuel is excessive and is corrupting the intake mixture, and leaking out the bottom of the plenum.

Why am I getting excess fuel to the VST? OR, is the amount normal and its just not being properly vented / directed BACK to the VST? After all, it has two nipples and hoses on its lid.

Looking forward to learning from Boscoe and Rodbolt on this.

My thought is, on that VST you have gone from "underfilling" to "overfilling".
And so liquid fuel, rather than air/vapor is exiting the vent.

cause? needle valve not sealing, float set wrong/hanging up, faulty lift pump pressure regulating valve

why are there two vent tubes on the VST top?

(as Boscoe as observed) I have already "vented" about that - twice.

[oldmako69]

It should be noted here that I did NOT mess with the VST on this engine. I did not open it, mess with the float, get jiggy with the needle valve, scrape the screen, etc.

I replaced the low psi pump and replaced the injectors. In order to do the injectors, I had to swing the VST forward to access their 'holder". That required me to remove a fuel hose or two. That's it.

[pstephens46]

Rodbolt would be good right about now.... I suspect you will be digging into that vst shortly.

[oldmako69]

I digs me some VST.

Actually, that's a big fat lie. Especially the STBD motor! Working on that side sucks.

I checked the dwell time at idle on the new lift pump by laying a big fat hand on it. It SEEMED to be functioning perfectly, 10 on and 20 off. Plus, its a 20 minute idle to the haul ass zone, so any issue with that engine ought to have become apparent. The problem was under WOT ops. Just like it was with my EX.

[pstephens46]

I digs me some VST.

Actually, that's a big fat lie. Especially the STBD motor! Working on that side sucks.

I checked the dwell time at idle on the new lift pump by laying a big fat hand on it. It SEEMED to be functioning perfectly, 10 on and 20 off. Plus, its a 20 minute idle to the haul ass zone, so any issue with that engine ought to have become apparent. The problem was under WOT ops. Just like it was with my EX.

What marina are you using in Va Beach?

[fairdeal]

It should be noted here that I did NOT mess with the VST on this engine. I did not open it, mess with the float, get jiggy with the needle valve, scrape the screen, etc.

I replaced the low psi pump and replaced the injectors.

Hmmm. Forgive me for not having paid close attention to those other posts -
but was that a "non Yamaha" pump?

We had a thread a while back, where the poster had a VST over-filling problem

he stated he had replaced his LP pump with an "eBay equivalent" -

and eventually reported,

that the output pressure of that replacement pump was so much more than the Yamaha pump

that it overwhelmed the pressure regulating valve, and forced fuel past the VST needle valve

I was skeptical - but that was his story.

[pstephens46]

And he was complaining about being depressed the other day....

[oldmako69]

Fairdeal,

Hey, that's GREAT intel. I still have the original and I will give it the old 1 2. As in Twelve volts. I am in possession of a fuel PSI gauge, perhaps that will be useful as I get Cro-Mag with this mother. But, I am not a mechanic, just a shade tree moron with wrenches and a computer. And, weird DNA which forces me to fix all of my gear. Or at least try to, before calling in the heavy artillery. That genetic defect is usually overridden by muffler and exhaust repair, septic tank service, dishwasher installation, tile floor removal, BIG tree work when they are close to my domo, AC evap replacement when its buried in the dash of my 32 year old 300CD, rat eradication in my crawl space, front end alignments, and roofing. I'm too old and too lazy for all of that.

pstevens46,

I do not use a Marina in VB. I have a "relationship" with a good friend on the water. I have a slip, a ramp, water and electric. Quid pro quo.

[fairdeal]

A simple check would be to swap the known, good YAMAHA pump to the other engine and see what happens...

that's a strategy.
Or with the engine off, you could tee in a gauge, run the LP pump, and check the pressure that builds once the VST is full.

On my F225TXRD, it was just over 14 psi



video:

https://vid.me/BZlf

[oldmako69]

Fairdeal,

You've exceeded my moron quotient by a significant margin.

How do you trick-F the LP pump to run with the engine off? Just apply 12V from a different source? Like, a motorcycle battery? Cuz, I gots one.

[99yam40]

how about turning on the key switch

[oldmako69]

I was under the impression that the key energized the high psi pump alone and that the low psi pump was not signaled to run until after start and at idle.

If you're correct, then thank you for the clarification and your oh so subtle rejoinder. I stand ridiculed, humbled in your shadow.

[pstephens46]

Fairdeal,

Hey, that's GREAT intel. I still have the original and I will give it the old 1 2. As in Twelve volts. I am in possession of a fuel PSI gauge, perhaps that will be useful as I get Cro-Mag with this mother. But, I am not a mechanic, just a shade tree moron with wrenches and a computer. And, weird DNA which forces me to fix all of my gear. Or at least try to, before calling in the heavy artillery. That genetic defect is usually overridden by muffler and exhaust repair, septic tank service, dishwasher installation, tile floor removal, BIG tree work when they are close to my domo, AC evap replacement when its buried in the dash of my 32 year old 300CD, rat eradication in my crawl space, front end alignments, and roofing. I'm too old and too lazy for all of that.

pstevens46,

I do not use a Marina in VB. I have a "relationship" with a good friend on the water. I have a slip, a ramp, water and electric. Quid pro quo.

Hmmm, sounds like some sort of a rich broad.

Boscoe would like you to post a pic of this person.