Fuel Water separator for 2019 Yamaha 70 hp 4 stroke

[Yamaha18]

Can anyone share what’s a good fuel/water separator (10 micron) for my 2019 Yamaha 70 hp (F70LA)?
i used it for only 25 hours using 6 gallons external tank and already experiencing fuel problem. Almost had to call TowboatUS. Was *****ing at 3.5 miles per hour and telltale water shot out suddenly became weak and motor started to choke or thirst for gas and died with 30% fuel left in tank. I switched to my 6 gallon (second) tank with full fuel (1 month old with ethanol additives) Was able to get the motor going after starting and motor ran a few seconds then died (3 times). Telltale water was strong again, motor ran fine after that. Unsure whether dirt got into the motor or water. My guess is the latter. Fuel is part 1 month old (with ethanol additive) and part 4 days old fuel.
Want to install a water fuel separator to get rid of future problems

[walleye1]

MAR-MINIF-LT-AS Made by Yamaha.

[robert graham]

The Walmart/Atwood unit for $28 is a good, inexpensive unit....I've had mine for over 10 years without issue....I use Ringfree and Stabil all the time.... My C90 Yamaha is a 1999 model and carbs have never been off. I do drain each carb for any lengthy lay-ups to be sure any water or debris is gone....just good preventive maintenance....

[DennisG01]

Any major manufacturer will be reliable. Yamaha, Mercury, Racor, Mallory, even Sierra.

Is your "first" tank a portable tank?

[TownsendsFJR1300]

Any major manufacturer will be reliable. Yamaha, Mercury, Racor, Mallory, even Sierra.

I think mine is a Sierra (aluminum). Painted it once (got salt corroded but caught it early), been on the boat about 20 years..

I would make sure you get one with the drain on the bottom (and see thru). Any water collected is very easily removed with the twist of the valve on the bottom.. No guessing if there's water in the filter either..

[pstephens46]

Happy with this one

[fairdeal]

Well, I'm going to be the contrarian here
and suggest that whatever your problem is,
"adding a fuel water separator" is introducing a red herring.

First, on a motor that size,
using portable plastic tanks,
you shouldn't need an additional boat-mounted filter.
Simply practice reasonable care in handling and storing your fuel tanks

Second,
your motor already HAS a "good fuel/water separator (10 micron)"
installed under the cowling -
with a water detection alarm.

whatever the cause of your recent experience -
it was unlikely that it was caused by 'bad gas' -
unlikely that it would have been "prevented" by having had an additional filter.

(More likely that your tank wasn't venting)

So my suggestion is that you

- read your Owner's Manual to learn about the undercowling filter,
then examine that for any sign of 'contamination"

- try to learn /understand how the fuel system works,
so that you don't have to pin your hopes on an imaginary magical band-aid

[rejesterd]

You might have water in your fuel tank, but a separator filter won't take out water that's built up in the VST and the fuel filter cup. I would drain the VST into a clear container (and then do the same for the fuel filter cup). If you don't find any water mixed in with the drained fuel, then you know that adding a separator filter won't fix your problem (and you can look for problems elsewhere). If you do find water in the drained fuel, then try only running it off the smaller 6-gallon tank which only has fresh fuel in it. Do this only after draining the VST and fuel filter cup. If the issue goes away, you know the problem is water in your tank. In that case, you should have the tank emptied and then install the fuel/water separator filter.

Also, when the issue happens again, open the fuel tank cap to see if the issue goes away. If so, you know it's caused by lack of venting.

The water exit stream can appear weak sometimes, especially when returning to idle from a higher speed. But even if you did have a problem with water cooling (which is unlikely considering how new the motor is), it wouldn't cause the engine to choke and stall out. The fact that the stream gets weak around the same time as it starts to stall out means that it's almost surely a fuel issue, not an issue with water intake. A clogged water passage wouldn't cause the engine to stall or run rough.

Also consider just taking it back to the dealer. It's so new, it's gotta be under warranty right?

[Yamaha18]

Both tank portable

Any major manufacturer will be reliable. Yamaha, Mercury, Racor, Mallory, even Sierra.yes
Is your "first" tank a portable tank?

[Yamaha18]

Whats VST?

You might have water in your fuel tank, but a separator filter won't take out water that's built up in the VST and the fuel filter cup. I would drain the VST into a clear container (and then do the same for the fuel filter cup). If you don't find any water mixed in with the drained fuel, then you know that adding a separator filter won't fix your problem (and you can look for problems elsewhere). If you do find water in the drained fuel, then try only running it off the smaller 6-gallon tank which only has fresh fuel in it. Do this only after draining the VST and fuel filter cup. If the issue goes away, you know the problem is water in your tank. In that case, you should have the tank emptied and then install the fuel/water separator filter.

Also, when the issue happens again, open the fuel tank cap to see if the issue goes away. If so, you know it's caused by lack of venting.

The water exit stream can appear weak sometimes, especially when returning to idle from a higher speed. But even if you did have a problem with water cooling (which is unlikely considering how new the motor is), it wouldn't cause the engine to choke and stall out. The fact that the stream gets weak around the same time as it starts to stall out means that it's almost surely a fuel issue, not an issue with water intake. A clogged water passage wouldn't cause the engine to stall or run rough.

Also consider just taking it back to the dealer. It's so new, it's gotta be under warranty right?

[Yamaha18]

Wow, 10 micron and fuel water separator under cowlings with 2019 YAMAHA 70 hp.
silly me!
i poured the fuel into a clear container and didn’t find any water but did find a lot of small solid rock from the gas i got from gas station. I cleaned (dried and vacuumed) my tank before i filled new gas to be used it for my new outboard.

so if i have 10 micron built in filter in my F70LA then that’s weird.

i did have the vent screw loose in my first portable tank and it ram fine for my last few outings. 2 of the trips i ran the motor all days non-stop like 9 hours and 8 hours in the ocean. Speed up and idle no issues at all until my last trip. Motor only has 26 hours. Yes under 3 years Warrenty until 2022.

Well, I'm going to be the contrarian here
and suggest that whatever your problem is,
"adding a fuel water separator" is introducing a red herring.

First, on a motor that size,
using portable plastic tanks,
you shouldn't need an additional boat-mounted filter.
Simply practice reasonable care in handling and storing your fuel tanks

Second,
your motor already HAS a "good fuel/water separator (10 micron)"
installed under the cowling -
with a water detection alarm.

whatever the cause of your recent experience -
it was unlikely that it was caused by 'bad gas' -
unlikely that it would have been "prevented" by having had an additional filter.

(More likely that your tank wasn't venting)

So my suggestion is that you

- read your Owner's Manual to learn about the undercowling filter,
then examine that for any sign of 'contamination"

- try to learn /understand how the fuel system works,
so that you don't have to pin your hopes on an imaginary magical band-aid

[Yamaha18]

Here is a pic of the dirt after i filtered the fuel back to my gas tank using toilet paper.

[Yamaha18]

Pic attached 61DD0D8D-02CE-4E50-AE05-0B6360B46DA2.jpeg

[Yamaha18]

A1E0CB63-99B3-4844-BB0D-B569959EDDB6.jpeg

[99yam40]

VST is Vapor separator tank.
that new F70 should be fuel injected
have you checked to see if the onboard filter has caught a bunch of that junk you show in the pic?
all of the gas pumps I have seen have filters on them, so I have no idea how that much debris got into your cleaned tanks