Mercruiser 3.0l TKS stalling

[mmtobias]

I have a 2009 Bayliner 175 with 3.0l mercruiser TKS engine. I have never had an issue with it before but yesterday I took it out for the first time this year. It started and idled fine as usual. I took it up to full speed for about 5 minutes to get to our fishing spot and then cruised at idle speed. Everything was fine for about another 5 minutes and then the engine stalled and died. I started it back up but it would only stay running at 3/4 throttle and above. So I raced back into the marina and when i slowed down to maneuver through the marina it kept dying again. I parked it in my spot in the marina and started looking at the engine to see if I could see anything obvious that came off or unplugged, but there was nothing noticeable. I took off the distributor cap that I replaced early last year and noticed the "anti corrosion" coating was flaking on the pins under the cap. I cleaned it off a bit with a screw driver and it started much easier and even idled for about 10 min. I turned it off and then restarted it right away and it would not stay running again. I left it for the night and spent the next few hours on google and this forum.

After some research it sounded like the TKS module might be the fault as it originally started after the warm up period. I went back to the boat and started it cold. It started and I could hear the loud hissing from the TKS module. I struggled to get it to run long enough, but after about 4 minutes I felt the back of the TKS module and felt that it was warm and then about 2 minutes later you could hear the hissing go away about 90%. I took off the spark arrestor and found the port that the TKS blocks but there was still a tiny bit suction coming from it. Is that normal?

Next I could get it to start again but as soon as I started to give it throttle it would stall again. No sputter or anything, just rev up to about 1800 rpm and then immediately stall, like someone turned off the key. I am thinking this is a fuel issue?? or airflow?? I was pretty sure that I had drained the fuel tank at the end of last season but then when I went to fill it up this spring it only took about 20L or so.

I have ordered a new distributor cap and rotor, plugs, wires and fuel filter and will try probably drain the tank and refill with new gas and a can of seafoam. Any other suggestions to check? should I pull that TKS module off and clean it anyway?

Any help would be greatly appreciated.

 

[Scott06]

I have a 2009 Bayliner 175 with 3.0l mercruiser TKS engine. I have never had an issue with it before but yesterday I took it out for the first time this year. It started and idled fine as usual. I took it up to full speed for about 5 minutes to get to our fishing spot and then cruised at idle speed. Everything was fine for about another 5 minutes and then the engine stalled and died. I started it back up but it would only stay running at 3/4 throttle and above. So I raced back into the marina and when i slowed down to maneuver through the marina it kept dying again. I parked it in my spot in the marina and started looking at the engine to see if I could see anything obvious that came off or unplugged, but there was nothing noticeable. I took off the distributor cap that I replaced early last year and noticed the "anti corrosion" coating was flaking on the pins under the cap. I cleaned it off a bit with a screw driver and it started much easier and even idled for about 10 min. I turned it off and then restarted it right away and it would not stay running again. I left it for the night and spent the next few hours on google and this forum.

After some research it sounded like the TKS module might be the fault as it originally started after the warm up period. I went back to the boat and started it cold. It started and I could hear the loud hissing from the TKS module. I struggled to get it to run long enough, but after about 4 minutes I felt the back of the TKS module and felt that it was warm and then about 2 minutes later you could hear the hissing go away about 90%. I took off the spark arrestor and found the port that the TKS blocks but there was still a tiny bit suction coming from it. Is that normal?

Next I could get it to start again but as soon as I started to give it throttle it would stall again. No sputter or anything, just rev up to about 1800 rpm and then immediately stall, like someone turned off the key. I am thinking this is a fuel issue?? or airflow?? I was pretty sure that I had drained the fuel tank at the end of last season but then when I went to fill it up this spring it only took about 20L or so.

I have ordered a new distributor cap and rotor, plugs, wires and fuel filter and will try probably drain the tank and refill with new gas and a can of seafoam. Any other suggestions to check? should I pull that TKS module off and clean it anyway?

Any help would be greatly appreciated.

What do the plugs look like ?

Would take off the fuel filter which is in the bowl on fuel pump see
What contents look like

When this happens do you have spark or a weak spark. I’d you advance the throttle does gas squirt
From accelerator pump nozzles

Might be worth looking at fuel pick up in tank and Anti siphon valve

 

[mmtobias]

I checked the front 2 plugs and the looked a little lean (white on the tip) no oil or gas on them and not wet. I was by myself so hard to bump the throttle and look at the carb but I did notice when I was looking after bumping the throttle to about 2500 rpm, the the fuel was just dripping into the carb. The boat is currently in the water at the marina so I will replace the fuel filter, cap, rotor, plugs and wires when I get the parts next week and I'll update you. I was wondering if there is something else I should be checking as well?

 

[dubs283]

I was looking after bumping the throttle to about 2500 rpm, the the fuel was just dripping into the carb.

If fuel is dripping from the venturi supply at that rpm there is a likely blockage somewhere in the carburetor. Time to tear down, clean, inspect and install new carburetor components. The tune up stuff your doing as well is great, part of routine maintenance

 

[alldodge]

I took off the spark arrestor and found the port that the TKS blocks but there was still a tiny bit suction coming from it. Is that normal?

No not normal, might need cleaned but may need replaced.
Remove it and check measurements cold and warmed up

 

[mmtobias]

Thanks for the info. I'll pull it off tomorrow and check. If I bench test it, can I just hook it up to a 12v car battery and then watch it expand for 8 to 10 minutes?

 

[alldodge]

Thanks for the info. I'll pull it off tomorrow and check. If I bench test it, can I just hook it up to a 12v car battery and then watch it expand for 8 to 10 minutes?

Yes, but most likely there is carb problems

 

[Scott06]

I checked the front 2 plugs and the looked a little lean (white on the tip) no oil or gas on them and not wet. I was by myself so hard to bump the throttle and look at the carb but I did notice when I was looking after bumping the throttle to about 2500 rpm, the the fuel was just dripping into the carb. The boat is currently in the water at the marina so I will replace the fuel filter, cap, rotor, plugs and wires when I get the parts next week and I'll update you. I was wondering if there is something else I should be checking as well?

If you disconnect throttle cable you can hand work the throttle at the engine.
when you say dripping into carb do you mean off the venturi boosters or overflowing the bowl? If bowl level is too high and overflowing either float/needle and seat is non functional or fuel pressure is too high

 

[mmtobias]

When I look into the carb there are 2 circles with holes in the middle. It drips from there. On the the flap for the throttle. I'll take a picture tomorrow.

 

[alldodge]

When I look into the carb there are 2 circles with holes in the middle. It drips from there. On the the flap for the throttle. I'll take a picture tomorrow.

Those are the venture's and a little drip is no issue. From your symptoms your most likely getting to much fuel so its flooding a little. This can be from a piece of crud getting in the carb needle seat, or just need to re-adjust things.

The enrichment module is not the overall cause, because it should still run but a bit rough if the module was not fully closing. Will need some investigating to find out what the issue is.

 

[dubs283]

Those are the venture's and a little drip is no issue.

Yeah, for a sound running engine with proper fuel delivery I disagree. A carburetor can be inspected, cleaned, rebuilt, and adjusted properly. Dripping down venturis means clogging somewhere, especially with a Rochester og/copy like OP's. Let's get a baseline with fuel pressure/vacuum while we're at it.....

 

[Scott06]

Yeah, for a sound running engine with proper fuel delivery I disagree. A carburetor can be inspected, cleaned, rebuilt, and adjusted properly. Dripping down venturis means clogging somewhere, especially with a Rochester og/copy like OP's. Let's get a baseline with fuel pressure/vacuum while we're at it.....

He mentioned gas coming off venturis at 2500 which is exactly what should happen when Venturi takes over from idle and transition system

 

[dubs283]

He mentioned gas coming off venturis at 2500 which is exactly what should happen

Agree, however a drip at that rpm, or any rpm for that matter is not normal. Either vacuum/timing issue or blockage in the carburetor

 

[Scott06]

Agree, however a drip at that rpm, or any rpm for that matter is not normal. Either vacuum/timing issue or blockage in the carburetor

It’s gas coming off the booster that’s how they work OP doesn’t know that when rpm comes up main boosters kick in

 

[mmtobias]

So to be clear, what should I see when looking in the carb at idle and at higher rpm? A drip or a spray?
For vacuum lines as well, I see a clear tube from the fuel filter to the carb, but nothing really else. My plugs are white and dry so I don't think it's running rich.
Thanks again for all the responses too. I used to be a mechanic before a career change 8 years ago, so I am mechanically inclined, but it was at a Toyota dealer so we didn't deal with carbs.

 

[alldodge]

Right now I'm not worried about a small drip because its all in an interpretation of what your seeing. As air is sucked in pass the venturi the low pressure sucks fuel out of the carb. The higher the rpm the more fuel is sucked out. Depending on how clean the carb internal channels are will depend how the pattern (drips, dribbles, spray) is.

With your plugs being white it could be the carb is clogging up and its not getting enough fuel. The lean condition can be caused by a restriction. Fuel filter, pump, lines and the antisiphon valve on the fuel tank. The valve is a barbed fitting that the rubber fuel line connects to.

Right now I would be looking at the carb and fuel filter. Dump the contents of the filter into a clear container to see if there is anything but clean gas

 

[mmtobias]

So, I was able to get out to the boat today but had to come in when the rain started. It started as usual but ran a little rough at the start. I could hear the Hissing from the TKS module. I tried to give it a little throttle to smooth out the idle and it died. 2 or 3 cranks later it started again and ran a bit smoother. I removed the spark aerrestor and looked in the carb and see nothing happening. I waited about 5 minutes and the hissing stopped. I covered the hole for the TKS and this time there was absolutely no suction so I am thinking its closed all the way. It was running pretty smooth at about 900 RPM (a little high) I took off the throttle linkage and gave it a shot of gas. I could see 2 streams of fuel enter the carb and then the engine died. I re started the engine in at 3/4 throttle and checked the carb. It appeared that there was spray from the 2 straps when i revved the engine earlier and drips from the Venturis. when I idle down slowly, as son as it gets to about 2000 RPM it just dies. Same as if i start it at idle and give it 1/4 to 1/2 throttle, it will rev to about 2000 RPM and die again. Also, if i let it idle it will idle fine for about 30 second and the choke out and die. Then it takes about 2 or 3 cranks and/or a few pumps of the throttle to get it going again so it seems like it is running out of fuel??? I am hoping the new fuel filter and such will arrive before the weekend so I can replace them and see what happens. I'll try to post a video of it stalling.

 

[mmtobias]

Here is a video of me trying to slowly Rev up the engine. The rpm start to climb and then it just dies. I'm having trouble getting the video to load

 

[Scott06]

Here is a video of me trying to slowly Rev up the engine. The rpm start to climb and then it just dies.

no video or link was attached

 

[mmtobias]

Sorry, it wouldn't let me upload the video. Try this link https://www.dropbox.com/s/zjmofn43u2o96xd/20220705_120647.mp4?dl=0