My Yammy 100HP strated running rough yesterday. I filled it up last fall-Oct, added Stabil,winterized it. I ran it a few outings this spring and ran ok and now I’m at less than 1/4 tank left and it idles but when I open it up it bogs right out and has no power. Could this be bad/old gas and low octane issue? Thoughts? Help! Thanks.
Start with cheap repairs. Fuel filter. New hose/ball pump on the fuel line.
Check the filter, you maybe sucking gunk from the bottom.
sounds like the lift valves may need new seals in the fuel pump. with the new gas we use, the seals get wrecked about every 5 years if you use seafoam or something to prolong that . would definitely do the cheap stuff first, but after that I would start here. not pricey but not cheap either.
While I understand that we HAVE to blame every motor malfunction on ethanol and bad gas, I hate to be the one to say that this, but it doesn’t sound like bad gas to me. You used stabilizer and if it were bad gas then you would have issues at idle as well, not just as you open it up. Bad gas is bad gas.
My initial best guess is a fuel flow issue. I’m with Matt, this sounds like a classic fuel supply / air leak so those would be the first things I’d check.
1. Change the fuel filter.
2. Thoroughly inspect the fuel hose and primmer bulb looking for any signs of cracking or air leaks. These can be hard to spot! The easiest way to diagnose a fuel hose air leak is to put on a different hose. If the problem goes away, you have found the culprit.
3. Now it gets more complicated. You also have to inspect the fuel lines under the cowling AND it is possible that the dip tube in the tank has cracked. Not saying that you can necessarily check these yourself, just calling them out as options. One of the most vexing “bogging down” problems I’ve ever seen turned out to be a cracked dip tube in the fuel tank. But it took us about 4-5 “other fixes” that didn’t fix it before we figured that out.
4. You don’t say if this is a 2 stroke or 4. Either way, I have to ask did you check the plugs? How did they look? Are they properly gapped using the exact setting supplied by Yamaha?
Grouse.
I’m guessing this is not the issue, but could it be as simple as too low on gas? A lot of times boat gas gages are not accurate, to me, less than 1/4 tank = E.
My 4 stroke yammie was doing the same thing after I used Stable. Motor guy says not to use that stuff. It creates a film over the top of the gas. When gas gets low you are probably picking up that film. A bottle of Sea Foam should clear it up. It did for me. Good luck
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