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Jay1234

Regular Contributor
Hey all,

Getting ready to install a 90gph Sierra marine water separator on my 90hp carb'd Johnson. (boat has built in tank, and is wet slipped all season) Started doing some reading and came across a few things indicating it may create a restriction in the fuel system. What is the general consensus on this? I know all the benefits of installing one, but are there many downsides?
Boat is used frequently. I add fuel probably every 2-3 days.
Should I remove the inline filter under the cowl after the sierra installation?
I know this topic has been discussed many times but in doing searches, as usual, I always seem to end up 50/50.
Thanks.
 
Hard to understand exactly what you are asking. If you are asking if you should run a water separator the answer is yes.

if you’re asking if you should run that separator with a fuel filter to avoid running it lean the answer is I’m not sure. I have a 225hp v6 Johnson ocean runner and I run both and I know it’s not running lean. Haven’t done the research to tell you if you should or shouldn’t but I don’t have a problem running both.

what I can tell you is water and dirt/grime will shorten the life of the block if not totally ruin it. As will running these motors lean. In other words, if I had your motor I would personally run both. Making sure it’s not running lean.
 
Thanks for the reply.

Separator is also a 10 micron filter. Just wondering if I should remove the small plastic inline filter after this install or leave it in place.
Curious as well as to if there are any potential issues using one with a relatively small outboard.

Thanks again.
 
The real problem here is in the chemistry of fuel today. Ethanol blended fuel will suspend the ethanol's weight in water.....mixing water with the ethanol. This will phase separate and cannot be remixed. In damp situations, this can occur in only a few months, additives cannot correct the situation, but might add a few months at best. The older fuel will not be "refreshed" with adding new fuel. The ethanol/water "compound"...will settle to the bottom of the tank. When you start up the motor, it will be the first to pass into the water separator because, of course, the fuel pickup is at the bottom of the tank. The fuel that is left becomes deprived of octane and can cause predetonation and other problems with your outboard, (or any motor/engine), eventually destroying it. The fix is: Use non oxy fuel......"an ounce of prevention is worth a pound of cure". Oxygenated fuels containing ethanol or other forms of alcohol are cleverly presented as helping the atmosphere, when in fact the opposite is true because of damage to equipment, poor economy, and high cost of manufacture/production. Our taxes go to reduce ethanol fuel prices through government support/incentives/tax credits.
Honestly, over 50 percent of my business here at my shop, is ethanol fuel related......including complete motor overhauls.
I'm still running both those motors behind me today, 45 years later, and if ethanol was around back in those days....... I'll tell you certainly that wouldn't be true. Ethanol is engineered to destroy our stuff and infuse the economy.
 

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Jay1234 said:
Hey all,

Getting ready to install a 90gph Sierra marine water separator on my 90hp carb'd Johnson. (boat has built in tank, and is wet slipped all season) Started doing some reading and came across a few things indicating it may create a restriction in the fuel system. What is the general consensus on this? I know all the benefits of installing one, but are there many downsides?
Boat is used frequently. I add fuel probably every 2-3 days.
Should I remove the inline filter under the cowl after the sierra installation?
I know this topic has been discussed many times but in doing searches, as usual, I always seem to end up 50/50.
Thanks.
Click to expand...

I don't know of many downsides, most of the boats I come across have at least 1 water separator, in varying distances from the tank, some are closer to the rear near the outboard, either under a rear hatch or mounted in the inner side of the boat, and I've seen some under the center console, closer to the onboard tank, or under the seat. I would suggest the closer to the engine the better, with enough run between it and your primer ball. The only restriction really would be an air lock or void, as you're adding one more access point for air in the fuel line. I pre-fill all the filters with fresh fuel before putting them on, not filling them with the primer ball. I personally would leave the under-cowl in-line filter, as it is more likely to pick up dirt particles than water. Are you going with a clear bottomed chamber or just a straight filter?
 
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