2012 3.0L TKS runs great with muffs, but slow on lake...

[ESGWheel]

The pressure showing on the inline gauge did drop as the throttle was increased. It was idling at like 4.5 PSI, then at double the throttle, the PSI went down to 4.2 PSI closer to 3000 RPM.

Were you underway or on the muffs for those readings?

 

[Lou C]

Someone here mentioned that I would have to take the exhaust manifold off then (replace the gasket) to check to see if the flapper was in place. When you say, "missing and blocking the exhaust", do you mean that it might have overheated, crumbled, fallen down the exhaust and it remains are now blocking out drive? The videos that I've seen, this flapper looks like a rubber butterfly that barely touches the exhaust. either round or oval shape. I've attached a picture of my exhaust where the flapper might be. The large U-shape piece is cast iron, then a rubber boot, then back to cast iron. Would I be taking off the rubber boot only, or the entire pipe to check? I do have a video borescope with a 15' cable if I can find a place to insert it. Thanks...

What you can try is to spray the part of the down pipe (below the rubber hose) with silicone, loosen the clamps and spray silicone in the joint between the hose and the exhaust elbow (top curved U shape piece of cast iron) and the hose. Let soak in for a bit. Then try the move the hose up and down, side to side, and slide it down onto the down pipe. Then you should be able to see the exhaust flapper and inspect it for free movement. If it's there and moving freely exhaust restriction is not likely your problem. If it's not then you got more work to do, let us know what you find if you do investigate this....

 

[Lou C]

The pressure showing on the inline gauge did drop as the throttle was increased. It was idling at like 4.5 PSI, then at double the throttle, the PSI went down to 4.2 PSI closer to 3000 RPM.
Anti-Siphon Valve - What am I checking for here? Blockage, if the check ball is missing? Thanks.

two things, the anti-siphon valve can be gummed up with crud inside, the ball can corrode in place but also the part that it screws into (the dip tube or withdrawal tube as it's called) can have a screen on the bottom that can be blocked by crud also.
You can rule these out without taking anything apart by running the boat on an outboard fuel tank. That eliminates the boat fuel tank as a potential problem and leaves you with fuel pump/carb exhaust restriction to check.
If you do be careful, I have a set up to do this with a 6 gallon outboard tank, I put a short length of hose after the barb and added a shut off valve, just in case the fuel line to the fuel filter ever leaks! Also be sure to plug the fuel line coming from the boat's gas tank to make sure no fuel spills in the bilge.

 

[GeorgioP07]

The pressure showing on the inline gauge did drop as the throttle was increased. It was idling at like 4.5 PSI, then at double the throttle, the PSI went down to 4.2 PSI closer to 3000 RPM.
Anti-Siphon Valve - What am I checking for here, the valve with the green marker line on it? Checking it for any blockage, clean it out, verify that check ball is in place? Thanks.

 

[GeorgioP07]

Were you underway or on the muffs for those readings?

This was all performed while the engine was running on muffs in the garage. As for getting out on the lake, I might, have one weekend left, sadly.....the temps are getting into the 50's now, and getting close to winterizing the engine either way.

 

[Lou C]

Yes to the question on the anti siphon valve. The ball must move freely and not stick. Be careful removing it. Look inside the hole in the fitting (top part of the fuel pick up tube) it's screwed into, do you see crud in there? If so it should be removed from the tank and cleaned out or replaced. Both the fuel pick up tube and the anti siphon valve have pipe threads, that should get a bit of fuel resistant sealant when reinstalling.

 

[GeorgioP07]

try the move the hose up and down, side to side, and slide it down onto the down pipe. Then you should be able to see the exhaust flapper and inspect it for free movement. If it's there and moving freely exhaust restriction is not likely your problem.

Alright Lou, Thank you. I will let the boot area soak in silicone spray overnight. Even if I can get a 10mm opening between the rubber boot and the cast iron, I can slip my boroscope camera down there and check out the flapper. Thanks.

 

[Lou C]

Here's one on my V6 4.3 Cobra. middle pic is new
top & bottom is burned up from overheat
had to pull the outdrive to get all the bits out lol.
This an OMC but Mercru is similar...

 

[Bondo]

What you can try is to spray the part of the down pipe (below the rubber hose) with silicone, loosen the clamps and spray silicone in the joint between the hose and the exhaust elbow (top curved U shape piece of cast iron) and the hose. Let soak in for a bit. Then try the move the hose up and down, side to side, and slide it down onto the down pipe. Then you should be able to see the exhaust flapper and inspect it for free movement. If it's there and moving freely exhaust restriction is not likely your problem. If it's not then you got more work to do, let us know what you find if you do investigate this....

Ayuh,...... Instead of silicone, use Quicksilver Power Tune,.....
It makes rubber slicker than snot,.....

 

[GeorgioP07]

Good news is that the flapper is 100% intact.
I was able to open the rubber coupler enough to look down inside and see it. As to how pliable it is , - I put a blank arrow down there and one of the rubber flaps moved, so I think that it is pliable enough.
Bad news is that the anti-siphon valve snapped off and left about 4 threads into the elbow that comes out of the gas tank. No sign of the check ball and spring unless they went flying, or are still stuck in there.
It seems to be one of the aluminum ones that you are supposed to avoid, but it was in there already, and I think, a bit corroded (dielectric, galvanic corrosion) with the steel elbow.
I tried to loosen the elbow and it's pretty snug. Do you have any ideas as to how to remove that, replace it, or what that part is called? Thanks...

 

[Lou C]

That’s the fuel pick up tube also called the fuel withdrawal tube. Use penetrating oil, time & patience. Do not force it work it back & forth just a bit spray more penetrating oil, get it to move a bit more etc. Dang aluminum!

 

[Scott06]

Good news is that the flapper is 100% intact.
I was able to open the rubber coupler enough to look down inside and see it. As to how pliable it is , - I put a blank arrow down there and one of the rubber flaps moved, so I think that it is pliable enough.
Bad news is that the anti-siphon valve snapped off and left about 4 threads into the elbow that comes out of the gas tank. No sign of the check ball and spring unless they went flying, or are still stuck in there.
It seems to be one of the aluminum ones that you are supposed to avoid, but it was in there already, and I think, a bit corroded (dielectric, galvanic corrosion) with the steel elbow.
I tried to loosen the elbow and it's pretty snug. Do you have any ideas as to how to remove that, replace it, or what that part is called? Thanks...

I ended up doing the same thing to my friends boat this summer (2000 or 2001 Glastron 185). He had water in the gas went to take off the AS valve and it snapped the same way. Who ever put the AS valve on at the factory over tightened it. I think they end up stretching the fitting when it is gorillaed in….

the dip tube in the tank should come out by unscrewing… I couldn’t get that out either, hopefully you have better luck.

As long as you can get the dip tube out of the tank you can just replace all if it.

 

[GeorgioP07]

Dip tube in the tank should come out by unscrewing… I couldn’t get that out either, hopefully you have better luck.

I was able to get the dip tube out by soaking the threads in a mixture of 2 parts acetone, 1 part brake cleaner, and 1 part red ATF.
Some brute force, and it finally let loose.
I was able to recover the spring from the anti-siphon valve in the bottom of the bilge, but I never did find the ball.
The screen at the bottom of the dip tube was very clean.
I was hoping to find it clogged, in order to explain things.
Anyways in choosing a replacement, I ran into some theories about using a anti-siphon vs. using a straight barbed fitting.
Some say that the anti-siphon only is useful when you have a fuel system leak.
The risk is using that the ball and or spring corrodes and you are stuck on the water with the motor starving for fuel.
Some say to get a dip tube without a screen to avoid blockage, some say get one with a larger openings.
Let me know what you think.
I tend to go with what was there, since the marine engineers (usually) know what they are doing.
Lots of dip tube kits are being sold with a brass straight barbed fitting.
I guess that they don't know or care that aluminum will eventually corrode brass. Thanks...

 

[Lou C]

Glad you got it!
Since you have an I/O it's highly advised to keep the anti siphon valve. Yes they can cause trouble but if the fuel line leaks between the tank and the fuel pump and if that fuel line drops below the level of top of the tank the fuel can siphon out of the line into the bilge creating an explosion hazard. That's the only reason that you have to have it.

 

[ESGWheel]

When you get your new Moeller pickup tube it will not come with a screen, as they stopped doing that. At least that is what the Moeller rep told me back in 2015. Also you will need to cut the tube, instructions should be included.

 

[nola mike]

The fuel pressure definitely did not double at 2500RPM, in fact, it went lower than it was at 850RPM idle.

Flow is not the same as pressure. As long as the pressure is still >4 or so you should be fine. This also rules out a downstream restriction, as mentioned earlier. Unless it's fuel quality, you don't have a fuel problem before the pump at this point. I also don't think this is flow related because you already have enough flow to idle and run. The bowl will be full when you up the throttle, so you won't bog until that gets exhausted. In other words, your rpms/speed should at least briefly rise when you increase throttle until the pump can't keep the bowl full. I'd also expect that if you were running so lean that you can barely plane out that you would be hearing some backfires/stumbling. I still think this is an electrical related misfire where you're dropping cylinder(s) at higher rpm. Did you ever put the timing light on the wires while underway? Seriously beating a dead horse here but you still haven't addressed one of the first troubleshooting steps you should have taken IMO. Ok, I'm done.