Low Fuel pressure issues - 1992 Grady-White Marlin w/ twin 2002 Yamaha 225 4 strokes

[seasick]

I am not aware of that feature but I guess it could be. I wonder if you run one motor only (let's say the one not having the issue) can you revs up to high revs. It seems to me that based on what you were told, you wouldn't be able to do that.

I am aware of motors that will not rev past a certain limit if not in gear. I wonder if your motor has that feature and the sensor that detects neutral is not working. If there is such a switch it will be on the bracket the shift lever and the shift control cable connect to. That 'neutral' switch is not the same as the one that the control uses to protect against starting the motor in gear.

 

[bob marlin]

If it was me, I'd be focusing on the things I mentioned above. It makes no sense to start disassembling things and/or replacing without first narrowing down the variables more. I feel like I may be repeating myself here, but why does the marina want to replace fuel lines when you/they verified the problem happened with a portable tank?

The reason for replacing the fuel lines is do to the age and the symptoms the motor is having. I also think there trying to eliminate another possible problem. When I ran the portable tank the motor still ran bad. I think this is do to the fact the filter most have been clogged and I was just running the gas in the portable through the clogged filter/screen in the VST tank it.

 

[bob marlin]

OK, that helps. That means everything upstream of where you connected the portable tanks is NOT the issue. Why is the marina suggesting replacing fuel lines when they are not the culprit? Forget about vents and such, as well. Assuming you used new/good fuel in the portable tanks, that also means fuel quality is not a possible culprit.

When you connected the portable tanks to the engine... where? Before or after the on-engine filter?

Now, you can look to engine stuff.

You mentioned you checked codes but didn't say if there were any?

What was going on with the fuel pressure while the issue happened?

After using the portable tanks with New Fuel I realized that I was just sending the new fuel through an already clogged system within the motor and the motors ran the same. So to me this did not rule out the house tanks and fuel lines. I think to rule out the house tanks and lines would you not need to get the motors running normal making sure all filters are clean and then run the portable tanks. You would also need to run them for a longer time to make sure there is nothing in the motor, i.e. fuel lines that would create the problem. Does this sound logical or am I missing the boat here.

 

[bob marlin]

I am not aware of that feature but I guess it could be. I wonder if you run one motor only (let's say the one not having the issue) can you revs up to high revs. It seems to me that based on what you were told, you wouldn't be able to do that.

I am aware of motors that will not rev past a certain limit if not in gear. I wonder if your motor has that feature and the sensor that detects neutral is not working. If there is such a switch it will be on the bracket the shift lever and the shift control cable connect to. That 'neutral' switch is not the same as the one that the control uses to protect against starting the motor in gear.

I have rev'd. the motors at the dock in neutral and they rev. easily up to 4000 rpms. Actually both motors have no problem rev'g. up to 4000 but his is not under load which is what the mechanic tells me is where the low rpm issue comes into play.

 

[DennisG01]

Does this sound logical or am I missing the boat here.

No, I don't think so. Or, at least, you're on the dock and the boat hasn't left without you, yet!

I thought you said the HP pump was replaced? There's no way you would have THAT much crap in the tank that it would clog the HP pump's filter up again, that quickly. The crap would have to get through two other filters, first... the boat mounted F/W separator and the engine mounted filter. Plus, you would see it in either the engine mounted filter, draining the F/W sep or draining the VST tank (which is super easy).

On the flip side... would it be a bad thing to replace the lines if you can verify that they are original? No, of course not.

And, yes, revving the engines in neutral is pretty much useless to diagnosis.

 

[bob marlin]

If you have the inline fuel pumps, they can be an issue but I would suggest bypassing one at a time. Install the primer bulbs but get good ones, the Yamaha OEMs are about $30
Changing the fuel line into the motor can be a challenge at times. First of all, make sure you get the correct fuel hose. It is probably 5/16 and not 3/8. Again but good quality hose rated A15. The hose from the primers back to the tank are 3/8 inch, same advice. Get good stuff. I am not convinced that the lift pumps are your issue. I just don't understand why when one motor bogs and you give it gas, the other motor bogs too. That has to be something that is common to both motors.
When you tried the portable tank, didn't you bypass the in-line fuel pumps?
Good luck with the search and let us know what the fix turns out to be. I am at a loss.

I will make sure any hose used are Yamaha OEM parts. When I used the portables I did bypass the inline pumps.

 

[DennisG01]

I will make sure any hose used are Yamaha OEM parts. When I used the portables I did bypass the inline pumps.

No need to spend money on Yamaha hose... if they even make their own hose, which I doubt. Trident or Shields - both are excellent hose manufacturers.

 

[bob marlin]

No, I don't think so. Or, at least, you're on the dock and the boat hasn't left without you, yet!

I thought you said the HP pump was replaced? There's no way you would have THAT much crap in the tank that it would clog the HP pump's filter up again, that quickly. The crap would have to get through two other filters, first... the boat mounted F/W separator and the engine mounted filter. Plus, you would see it in either the engine mounted filter, draining the F/W sep or draining the VST tank (which is super easy).

On the flip side... would it be a bad thing to replace the lines if you can verify that they are original? No, of course not.

And, yes, revving the engines in neutral is pretty much useless to diagnosis.

It must be that its early in the morning, I have'nt had a cup of coffee whatever but Im good with the ruling out of the house tank/lines. The HP pump was replaced and as I said earlier the boat ran good that next day but half way through the second day the problem reoccured. The mechanic pulled apart the tank again partially due to a leak in the new o-ring they installed and found that the new filter/screen was plugged already. He sent me photos and it was pretty bad. I was told that they did not clean the inside of the tank and the existing build-up material re-clogged the filter/screen. The new marine wants to take the VST tank apart to check to make sure it was put back together correct along with checking the injector screens as well. Does this sound like a correct approach.

 

[DennisG01]

Sure, can't hurt to double check things on the inside of the VST tank.

As far as the injector filters... If it was me, I would just send all of the filters out to be refurbished (professionally cleaned, tested for proper flow, filters changed). Typically about $20/injector. If the marina doesn't know anything about this, no worries. Look around your town for an injector shop - if they're halfway decent, it won't matter if they don't normally do marine stuff -it's the same as automotive and they'll recognize it. Or, there are places you can ship them to.

 

[seasick]

If the fuel rail pressure is low, there is no immediate need to pull the injectors. Yes they may be an issue but wouldn't account for the low fuel pressure.

The VST screen clogging so fast is possible if the VST tank was full of gunk, perhaps the white powder problem. That would explain a lot but not all of what you describe.
And as Dennis mentioned, don't waste your money on Yamaha fuel lines. I like the Shields brand just don't skimp on quality.

One comment about the finding of a poorly seated cover gasket. If the VST cover is leaky, in theory that won't cause performance issues if everything else is correct like the high pressure pump seall. The VST tank with the float is not under pressure and is actually vented to the atmosphere. Of course, some gas could slosh around and leak out.

It is a shock to learn that a mechanic changed the VST screen and gasket as well as perhaps the high pressure pump and didn't inspect and clean the VST bowl. Maybe I read that wrong.

Once again ask your mechanic if there is a filter in the output of the fuel pressure regulator and if so, have it inspected and probably changed. When dirty, that can cause low fuel pressure.
The screen is not on all models.