Expert advice needed for a Fuel Delivery issue?

[Cary]

HI Everyone, I purchased a 2002 300 Marlin in March this year. Great boat and has been a joy to operate. I recently had a problem with one of the engines (225hp four stroke) shutting off due to fuel starvation at idle to just above. It's wierd, only happened a couple times with 5-6 hours between and i was able to pump the primer bulb and get it going again. After the first time it happened i changed the fuel filter at the engine thinking it may be clogged. Clean as whistle, the fuel oil separators are changed every year and were changed prior to storage along with all the filters. Engines probably have 20 hours since everything was serviced. The prior owner was very diligent about maintenance.

The problem just happened again this weekend and this time i couldn't get the primer bulb to fill with fuel to get it going again? I have switched tanks trying to isolate the problem to one tank. This weekend it actually happened to the other engine as well which made me think this is not a engine releated issue but some type of air leak in the line or something. The other engine was a first and just a primer bulb squeeze a couple times allowed it to restart and never miss a beat again.

I have run about 300 gallons of fuel through the engines since i have gotten them so i am pretty sure it's not fuel. I took off the one fuel/oil separator when it happened this weekend and dumped it looking for water in the fuel and saw nothing but clean fuel. I thought could this be a flop tube issue in the tank but when switched tanks it didn't fix it?

Any ideas of what next to try? I was thinking of changing both the primer bulbs next?

Thank you for any input
Cary!

 

[SkunkBoat]

Fuel tank vent line clogged
Air leak in fuel line connections
fuel pump
primer bulb arrow not pointed up at motor

 

[Cary]

Thank you for the ideas, i have not thought about a fuel tank vent line clog but wouldn't switching tanks eliminate most of these issues? The primer bulbs have been in place for a long time with zip ties, the one going to the port motor which has developed the problem is moving up in a vertical direction but curiously the starboard engine without much of a problem has the primer bulb more horizontal. I will pull that one to vertical, i didn't know they need to be more upright if that is what your saying by pointing at the engine?

Thanks
Cary!

 

[seasick]

If you have starvation issues at low revs but not high, the primer bulb would not be my first suspect. Nor would a clogged vent. I would think low pressure pumps or the lift pump if you have them. I would also suggest that you check the fuel filter bowl to make sure it is seated correctly. In normal condition it will be more than half full but not completely full. If empty you do have a fuel starvation issue. If full, you have an air leak, probably a leaking fuel bowl.
For the record, I am not an expert!

 

[Ky Grady]

But you slept at Holiday Inn Express!!!

Sorry, us older folks should understand seasick.

 

[seasick]

You know you are really old when you can't remember where you slept last night!

 

[Cary]

Thanks Seasick, I watched the fuel bowl as it was running. It was a little over half full but it moves up and down a little bit? Is that normal or would that possibly show an air leak. I have replaced the filter, the bowl seems tight and secure but would be hard to detect an airleak? No fuel leak that i can see. Wouldn't it be odd that both fuel pumps would go bad at the same time? Most of this issues has been on the port engine but the other day it happened to the starboard engine once? That to me would somewhat rule out pumps, fuel bowl leaks, etc. I guess if the engines are the same age and hours 1500, things could go bad at the same time. puzzling!!

 

[seasick]

Thanks Seasick, I watched the fuel bowl as it was running. It was a little over half full but it moves up and down a little bit? Is that normal or would that possibly show an air leak. I have replaced the filter, the bowl seems tight and secure but would be hard to detect an airleak? No fuel leak that i can see. Wouldn't it be odd that both fuel pumps would go bad at the same time? Most of this issues has been on the port engine but the other day it happened to the starboard engine once? That to me would somewhat rule out pumps, fuel bowl leaks, etc. I guess if the engines are the same age and hours 1500, things could go bad at the same time. puzzling!!

Your fuel bowl sounds normal. If the bowl seal leaks air, the bowl fills up. If there is an air leak in the section between the bowl and the tank, the bowl will usually empty.

It would be unusual for lp pumps to go bad at the same time on both motors.(but not impossible). Do those motor have an electric lift pump?



The more I think about this, the more I suspect an air leak and that would have to be between the tank selector and the primer bulb.
You stated that switching tanks didn't help so that eliminated some fuel line, anti-siphon, the pickups and the tank vents . There aren't too many common components other than the gas itself assuming both the main and aux tanks might have bad gas.
I am stumped. Keep us informed.

 

[Finest Kind]

I would first isolate the problem as follows:
Disconnect the fuel line from the problem motor at the primer bulb.
Connect that fuel line back onto the motor using a portable tank with fresh, clean gas.
Now run the motor off the portable tank....

If the problem disappears, the issue is in your boat.
Check the fuel filers again to ensure they are seated properly, the fuel lines and tank selector valves for leaks, the anti-siphon valves and the tank pick-ups for debris on the intakes.

If the problem re-occurs the issue is somewhere within the fuel delivery system inside your motor.
Check the internal filters.

 

[Cary]

Thanks Seasick and finest kind. I am suspecting an air leak between the selector and primer bulb as well. I noticed one time not long after i got the boat a couple months ago a little fuel around the fuel selector. This could be a small leak and possible air as well, it wasn't dripping or anything i just noticed a little wetness.

Finest kind, the problem with isolating the tank is hard because the problem is so random? It has only happened twice in 20 hours. The last time over the weekend once i got it going it didn't miss a beat again for the next 2 hours? Now because the problem was the worse it's been over the weekend maybe it will happen again more frequently and i can isolate the tank as you said and that sounds like a good idea. I am going to see what type of O Rings are in the fuel selector valves and maybe try to replace them as well as replacing the lines from the selector to the primer bulb as well as new primer bulbs i guess.

This is a tough one!

 

[glacierbaze]

The float in the center of this f115 filter bowl shows water below and gas above. When the water forces the float to the top it cuts off flow to the engine. Perhaps at speed, there is enough turbulence in the bowl to allow fuel to pass, but not at idle. Have you checked that float level?

 

[georgemjr]

"F" filter on the motor might be worth taking a look at.

 

[Ky Grady]

"F" filter on the motor might be worth taking a look at.

Good call on that filter. It's often overlooked and it hides in plane sight with the rubber cover on my F225.

 

[Cary]

Thank you glacierbaze, I changed the fuel filter on the port engine and it was clean as a whistle, I didn't see any water at all in the fuel bowl and the Starboard engine had the same issue once only so I am thinking it's a fuel delivery issue?

Thank you georgemjr, where is the F filter?

 

[georgemjr]

It is an inline filter (fine screen) in the fuel line. Mine clogged while all the other screens/filters were still okay. Happened to my buddy as well. I would be lying if I tried to pretend to give you the exact location. I think I remember removing one of the intake manifolds to get to it (super easy).

 

[Ky Grady]

Here's the location for F225. It is above the VST, port side and at the front. Can't remember if it's visible with the intake on, I'm thinking it is.

 

[Sharkbait282]

Check the bottom surfaces of your mounted 10 micron fuel/water filters with a photo. If they look like this, it's really easy for them to have an air leak, even if you feel like you've screwed the filters on tight. The corrosion makes it difficult to gain an adequate seal.

I also had this issue and also went so far as to pull the deck plate and replace the 4 anti-siphon valves on the tank pickups. But these canisters is your primary opportunity for an air leak between the selectors and the primer bulbs, and it's where I was pulling air with motors of a similar vintage. Best of luck!





Feel free to reach out with any questions!

 

[seasick]

Great photo. I guess what they say "a picture is worth a thousand words" is true.
The flange can be scrapped and then sanded with fine emery. Usually they will clean up nicely.

 

[Sharkbait282]

Great photo. I guess what they say "a picture is worth a thousand words" is true.
The flange can be scrapped and then sanded with fine emery. Usually they will clean up nicely.

I am also not an expert . . . I wouldn't have even thought of scraping and refinishing. The stainless steel versions of the filter housings were just too nice looking for me to pass up!

 

[Cary]

It is an inline filter (fine screen) in the fuel line. Mine clogged while all the other screens/filters were still okay. Happened to my buddy as well. I would be lying if I tried to pretend to give you the exact location. I think I remember removing one of the intake manifolds to get to it (super easy).

Thank you for the picture. I will check it out.