4 strokes and primer bulb issue?

[Bass Cat Boats]

Some engines may require a separate fuel pump, or you can go to a larger Yamaha 350 Primer bulb.

The issue is in the tank pickup and on the most common brand those are a maximum of 5/16” and are restricted. The most common fitting size on the output for newer fuel demand valves is 1/4” and that is not enough. This is why engine companies have stepped up to seek better fuel delivery in pumps, when the real issue was masked by fuel quality until about 1 year ago.

so... an in line fuel pump or larger primer bulbs are possible.

[th365thli]

Some engines may require a separate fuel pump, or you can go to a larger Yamaha 350 Primer bulb.

The issue is in the tank pickup and on the most common brand those are a maximum of 5/16” and are restricted. The most common fitting size on the output for newer fuel demand valves is 1/4” and that is not enough. This is why engine companies have stepped up to seek better fuel delivery in pumps, when the real issue was masked by fuel quality until about 1 year ago.

so... an in line fuel pump or larger primer bulbs are possible.

My question is, if it's the fuel pickup why hasn't this issue manifested until now?

[Bass Cat Boats]

Fuel pumps weaker over time...

they have a lot of vacuum pressure on them.

[ChampioNman]

Fuel pumps weaker over time...

they have a lot of vacuum pressure on them.

If that's the case it doesn't say much about build quality of a less than two year old component.

[th365thli]

If that's the case it doesn't say much about build quality of a less than two year old component.

Going to have to agree. The motor barely has 20-25 hours on it. Fuel pump should not be failing at this point. Also, we found that the problem is only reproduced if we don't prime the bulb. Once we prime the bulb, the boat runs fine. I didn't run it for an hour or anything like that, but we were able to run an extended amount of time to get to our next spot and the ramp. Whereas if I didn't prime it, it would shut down pretty quick. That being said....I'm not a mechanic or a boat builder, so anything is possible. If it is the engine fuel pump, that honestly might be better for me as I'm still under warranty.

[Jumping Jimmy]

I have been going through this same issue with a one year old Mercury 200 Optimax ProXS on a 2004 Stratos. My boat had the same symptoms. I had the dealer replace the low pressure pulse pump but that did not help. After several discussions with the dealer he was convinced it was a fuel delivery problem. First I connected my engine to a remote 6-gallon fuel tank and my engine ran fine on it. This ensure that my issue was indeed with my boat.

I removed the seats and seat pan assembly to access the fuel tank. I replaced the 3/8" original fuel line, the pickup tube and replaced the anti-siphon valve with a barbed hose connector. I made sure the vent was clear as it would be a major pain to replace the vent assembly. I have run the boat several times with these repairs and I no longer have a fuel delivery issue. My fuel line appeared fine to me and I suspect the anti-siphon valve to be the culprit. I continue to have idle issues but there is fuel to the engine so on to the next issue..

With your newer boat there could be a problem with the new design vent system not allowing the tank to breath properly.

[DrewFlu33]

A quick way to tell if it's the vent on the tank(s) would be to loosen the gas cap a bit. Obviously you don't want to leave it that way as you risk water splashing in, but it should allow you diagnose whether the vent is the problem fairly quickly. Hell, you might even be able to tell without running it if you loosen the gas cap soon after the problem shows itself...if it's a venting issue, you'd hear air rush around the cap when you loosened it or would otherwise have a difficult time loosening it.

If that doesn't change anything, given the info provided by BCB and others, it sounds like the small outlet on the primer bulb is the most likely culprit!

[th365thli]

I have been going through this same issue with a one year old Mercury 200 Optimax ProXS on a 2004 Stratos. My boat had the same symptoms. I had the dealer replace the low pressure pulse pump but that did not help. After several discussions with the dealer he was convinced it was a fuel delivery problem. First I connected my engine to a remote 6-gallon fuel tank and my engine ran fine on it. This ensure that my issue was indeed with my boat.

I removed the seats and seat pan assembly to access the fuel tank. I replaced the 3/8" original fuel line, the pickup tube and replaced the anti-siphon valve with a barbed hose connector. I made sure the vent was clear as it would be a major pain to replace the vent assembly. I have run the boat several times with these repairs and I no longer have a fuel delivery issue. My fuel line appeared fine to me and I suspect the anti-siphon valve to be the culprit. I continue to have idle issues but there is fuel to the engine so on to the next issue..

With your newer boat there could be a problem with the new design vent system not allowing the tank to breath properly.

Thanks for the datapoint, since it's a 2004, I assume they hadn't switched over to the new pressurized fuel systems yet? So your tanks was still being vented the "old way"? I couldn't find a vent on the boat, then I did more research and now the fuel tanks are pressurized. This explains the air being released when I pop open the gas cap.

[th365thli]

A quick way to tell if it's the vent on the tank(s) would be to loosen the gas cap a bit. Obviously you don't want to leave it that way as you risk water splashing in, but it should allow you diagnose whether the vent is the problem fairly quickly. Hell, you might even be able to tell without running it if you loosen the gas cap soon after the problem shows itself...if it's a venting issue, you'd hear air rush around the cap when you loosened it or would otherwise have a difficult time loosening it.

If that doesn't change anything, given the info provided by BCB and others, it sounds like the small outlet on the primer bulb is the most likely culprit!

Air releases from the cap when I pop it open (it's a latch style, not screw). That's normal I think because of the new EPA regulations that require fuel tanks to be sealed. I'm actually not sure how venting works with this new style. So far the most likely culprits are the primer bulb, anti siphon valve (if i have one), venting issues, or a faulty low pressure pump. I don't it's a venting issue since the boat runs fine after pumping the primer.

Can someone explain to me how fuel stays in the line such that the engine can be started at the first key turn, even after sitting for a while? Is it because the check valve on the primer bulb? The pump that activates when the key is turned? The anti siphon valve? Or all 3? My old 1987 carbureted two stroke needed to be primed before every trip. And I had to gas it a little to start it every time. Modern 4 strokes are nice since you just turn the key and it starts like a car. Just curious what they do to allow you to "turn key start" every time.

[woppercatcher]

Not sure about other brands but my Yamaha after only 6 months it died going down the lake like it was out of gas. I had to keep priming the bulb to get it to idle back to the ramp. It was the lift pump that had to be replaced. I've never primed the bulb from the time I bought the boat until now and don't plan on it otherwise. I'm not even sure why it's there at all but I was told when I bought the boat there was an issue where Skeeter mounted the bulb/host vertical in the bilge and that was causing issues where the boat would stop running like mine did. The fix was to ensure the bulb/hose was mounted horizontally instead, go figure.

[DrewFlu33]

Air releases from the cap when I pop it open (it's a latch style, not screw). That's normal I think because of the new EPA regulations that require fuel tanks to be sealed. I'm actually not sure how venting works with this new style. So far the most likely culprits are the primer bulb, anti siphon valve (if i have one), venting issues, or a faulty low pressure pump. I don't it's a venting issue since the boat runs fine after pumping the primer.

Can someone explain to me how fuel stays in the line such that the engine can be started at the first key turn, even after sitting for a while? Is it because the check valve on the primer bulb? The pump that activates when the key is turned? The anti siphon valve? Or all 3? My old 1987 carbureted two stroke needed to be primed before every trip. And I had to gas it a little to start it every time. Modern 4 strokes are nice since you just turn the key and it starts like a car. Just curious what they do to allow you to "turn key start" every time.

I thought the EPA rules were only for portable fuel tanks and just assumed fuel tanks on new boats are vented the same as old ones, but I suppose I honestly don't know that.

[Bass Cat Boats]

EPA an on evaporation requirements have changed fuel systems and the newer tanks are also why the fuel demand valves are not proper sized. Which has been a part of the fuel pump issue these past few seasons. Every manufacturer is dealing with this at different degrees.

[th365thli]

Got the boat back today.

The dealer/mechanic was pretty certain it was vapor lock. He checked fuel and ran diagnostics on the engine. He said he also ran it on the lake a couple times and couldn't reproduce the error. As an engineer myself (albeit software), I know how frustrating intermittent issues can be to solve. He said it's more common among the lower horsepower inline 4 Suzukis, but it's not outside the realm of possibility.

Apparently it can happen when temperatures are just right, and/or if you immediately cut off the motor after hard running. It just so happened that the day I saw symptoms was when air temperatures were hot (80s), but water temperatures were still cool (low 60s), hadn't caught up yet. At any rate, I'm just glad to get the boat back. I happen to trust this dealer, they have have service awards from Suzuki and have a good local reputation. Hopefully it doesn't happen again, or if it does, some idling after hard running will fix it.

[Bass Cat Boats]

It is fuel pressure related as we said.

[th365thli]

It is fuel pressure related as we said.

Well, it seems you are correct. When I ran it out today same symptoms. First crank of the day it ran fine. Fished first spot 10-15 minutes. Ran fine again. Fished second spot at least 2 hours. Lo and behold, when I got up in plane and started running it cut rpms and the engine shut off.

Turns out my mechanic misunderstood me, when he ran it, he never cut it off, he just ran it hard then retrieved it. Seems like this issue needs a period of time between cranks to be reproduced. He did tell me to check the bulb, to the fuel demand valve, to the anti siphon valve. He didn't think it was an issue with venting.

@Bass Cat Boats, you earlier your suggested an inline fuel pump or larger primer bulb. I'm leery of putting an electric inline fuel pump in my bilge where condensation/water is a possibility. Would you still suggest a 350 size primer bulb?

Moreover, I can circumvent this issue by just squeezing the bulb until it's firm. However, any idea on why on the first crank of the day, after it's been sitting in my storage, it works? And it's only after I run that the issue manifests? My uneducated guess is that when it sits for a while, pressure in the tank builds up. After running however, the that pressure is removed.

[th365thli]

I just called Opie at Falcon Boats and he told me how to pop off the tank cover and inspect the tank. He said he's heard of a couple issues with fuel demand valves. They use 3/8 inch fuel lines. Looks like I have a bonafide project on my hands.......