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Started By
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Outboard motor, bad gas? How to fix?
Posted on 6/14/25 at 1:42 pm
Posted on 6/14/25 at 1:42 pm
Picked up a boat from a family member that has a relatively new and nice Yamaha outboard. The gas in it is likely 2-3 years old.
Took it out for test run last week and it cranks up immediately, idles fine and can run up to about 2,500 RPM sounding pretty normal.
But when I try to get on plane, it runs up to 5-6,000 RPM mostly normal, but then starts to sputter and cough and loses power and RPM.
I'm assuming it's the gas.
IF you think so, what's the best thing to do? It's got about a 1/4 tank in it. Should I put some additive "gas revitalizer" kinda stuff and then fill it up with a good non-ethanol gas and just keep running it?
Or drain it and go all fresh?
Or something else?
Thoughts?
Took it out for test run last week and it cranks up immediately, idles fine and can run up to about 2,500 RPM sounding pretty normal.
But when I try to get on plane, it runs up to 5-6,000 RPM mostly normal, but then starts to sputter and cough and loses power and RPM.
I'm assuming it's the gas.
IF you think so, what's the best thing to do? It's got about a 1/4 tank in it. Should I put some additive "gas revitalizer" kinda stuff and then fill it up with a good non-ethanol gas and just keep running it?
Or drain it and go all fresh?
Or something else?
Thoughts?
15
Posted on 6/14/25 at 1:50 pm to Meauxjeaux
Gas lines could be gummed up.
Take off engine and make sure you have free flow.
Put some gas in a clear container.
If it orange. Get rid of it all and flush lines.
Check fuel filters as well. They can hold water and gum up.
When you check the gas, try to get as much as you can from bottom of the tank. Check for water. You would be surprised how much water can get into your gas system over time.
Take off engine and make sure you have free flow.
Put some gas in a clear container.
If it orange. Get rid of it all and flush lines.
Check fuel filters as well. They can hold water and gum up.
When you check the gas, try to get as much as you can from bottom of the tank. Check for water. You would be surprised how much water can get into your gas system over time.
Posted on 6/14/25 at 2:29 pm to Meauxjeaux
Sounds more like a fuel supply issue to me. If it'll make full power and then starts losing it, its probably a supply issue and not a fuel issue.
Filters, screens, hoses, etc etc
Filters, screens, hoses, etc etc
Posted on 6/14/25 at 3:13 pm to Meauxjeaux
Which motor? Had same situation when I bought my boat (Yamaha f115) and thought it was the gas. VERY similar symptoms as you mentioned. Ended up being the injectors. Once I had those cleaned, it ran like a top. Apparently quite common with that motor.
Disconnect the fuel line and run it from a jug of fresh gas. Should answer the fuel question.
Disconnect the fuel line and run it from a jug of fresh gas. Should answer the fuel question.
This post was edited on 6/14/25 at 3:15 pm
Posted on 6/14/25 at 3:56 pm to Meauxjeaux
I would drain and replace fuel lines if possible. Sometimes the inside lining of them delaminate. Better than running crap through the motor.
Posted on 6/14/25 at 4:20 pm to DownshiftAndFloorIt
quote:
Sounds more like a fuel supply issue to me. If it'll make full power and then starts losing it, its probably a supply issue and not a fuel issue.
Filters, screens, hoses, etc etc
This is the answer.
Posted on 6/14/25 at 5:46 pm to speckledawg
Sounds like what mine was doing when injectors needed to be cleaned.
Posted on 6/14/25 at 10:29 pm to speckledawg
quote:
Which motor? Had same situation when I bought my boat (Yamaha f115)
Gonna go see it tomorrow.
Thanks all for the info here!
Posted on 6/15/25 at 8:25 am to Meauxjeaux
Run ethanol free and Stabil Storage going forward.
Posted on 6/15/25 at 9:32 am to Meauxjeaux
Go buy a new 2-3 gallon tank with new hose and bulb and go run it. If it runs fine you have a problem with your fuel or fuel lines.
If thats the case.
Drain the tank and refill fresh
Disconnect the gas hose from the motor
Pump the bulb and dump the gas into a container
Replace all fuel lines and bulb
Go run it
If thats the case.
Drain the tank and refill fresh
Disconnect the gas hose from the motor
Pump the bulb and dump the gas into a container
Replace all fuel lines and bulb
Go run it
This post was edited on 6/15/25 at 9:33 am
Posted on 6/15/25 at 9:40 am to Meauxjeaux
If it's an outboard, just hook up another tank of feesh fuel and test.
Posted on 6/15/25 at 9:42 am to Meauxjeaux
Run some seafoam through it too.
Posted on 6/15/25 at 10:35 am to Bigsampson
quote:
Gas lines could be gummed up.
Take off engine and make sure you have free flow.
Put some gas in a clear container.
If it orange. Get rid of it all and flush lines.
Check fuel filters as well. They can hold water and gum up.
When you check the gas, try to get as much as you can from bottom of the tank. Check for water. You would be surprised how much water can get into your gas system over time.
^^^
Follow this post exactly. Inexpensive trouble shoot before you get into more complicated and expensive stuff.
Posted on 6/15/25 at 1:08 pm to Tridentds
Maybe it was just time for me, but I also suspect the freeze this winter did a number on some of my fuel hose ends, especially if coming into a barb at a bend.
When replacing lines and filters/filter o-rings, make sure there’s no air getting sucked in the fuel line.
When replacing lines and filters/filter o-rings, make sure there’s no air getting sucked in the fuel line.
Posted on 6/15/25 at 5:40 pm to Meauxjeaux
I would put money it’s water in the gas if it’s been sitting. Get a water fuel separator.
Posted on 6/15/25 at 5:49 pm to Landmass
Fresh gas and seafoam.
Posted on 6/16/25 at 10:21 am to Meauxjeaux
Drain and fill with fresh gas, Google mercury quicklean cocktail. I believe Techron is the same and cheaper, run multiple tanks through with additive. The more you burn the better off your motor will be.
Posted on 6/16/25 at 10:23 am to Meauxjeaux
you ran it with gas 2-3 years old?
hopefully you didn't damage the power head
hopefully you didn't damage the power head
Posted on 6/16/25 at 4:00 pm to Meauxjeaux
Have dealt with this issue a lot with boats that have been sitting a long time with ethanol gas.
I'd drain down the tank completely and change the fuel filters.
If the gas has any kind of orange tint to it or a distinctive sweet smell then its for sure bad and you might have a blob of separated ethanol floating around in the tank. Might take off the fuel sender to look down in there.
Separated ethanol can clog the screen on the fuel pickup at the bottom of the tank.
Would also keep in mind that primer bulb has a check valve in it that can also get fricked up. The bulbs themselves are cheap and tend to fail when old.
Also what the poster said above about the inside of the fuel lines deteriorating, have seen that as well.
Change filters and drain down the fuel rail to get clean gas up to the injectors and purge the air out of the fuel rail.
Bad ethanol gas is nasty stuff and causes all kind of expensive problems.
I'd drain down the tank completely and change the fuel filters.
If the gas has any kind of orange tint to it or a distinctive sweet smell then its for sure bad and you might have a blob of separated ethanol floating around in the tank. Might take off the fuel sender to look down in there.
Separated ethanol can clog the screen on the fuel pickup at the bottom of the tank.
Would also keep in mind that primer bulb has a check valve in it that can also get fricked up. The bulbs themselves are cheap and tend to fail when old.
Also what the poster said above about the inside of the fuel lines deteriorating, have seen that as well.
Change filters and drain down the fuel rail to get clean gas up to the injectors and purge the air out of the fuel rail.
Bad ethanol gas is nasty stuff and causes all kind of expensive problems.
This post was edited on 6/16/25 at 4:01 pm
Posted on 6/16/25 at 5:11 pm to Meauxjeaux
Shoulda drained that sucker right if the get go regardless of him much was in it. Drain refill treat it with Heet. Then see what u got.
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