In hull gas tank...how to get fuel/oil mix into engine

Okay, so i have an in hull tank that has been cleaned by previous owner about two years ago but haven't used it. Have been using external red tanks. Since everything is in running condition, I haven't been very busy lately and need something to do and thought this was a perfect thing to try and rig. Anyway, I have looked at the setup in the bilge area of the boat( 1987 17 ft Seaway CC) and have found a fuel filter/ water separator which appears to note that you can't put oil in it like a fuel/oil mixture. Also there are two fittings that surface in the splashwell, one is the fuel line coming from the fuel filter/water separator which would supply the gas to the engine, and the other seems to be a vent possibly which under the splaswell in the bilge is a fairly large hose compared to the fuel hose. So I have a 1982 Evinrude 70hp and I don't know if I can put an external oil tank in the fuel system or if because the engine isn't a VRO, it won't work. Anyone with information, thank you for chiming in.

I would like to get this working in order to rid the external tanks which take up deck space if at all possible.

Re: In hull gas tank...how to get fuel/oil mix into engine

There are water seperators/fuel filters that do not have issues with premix.

Re: In hull gas tank...how to get fuel/oil mix into engine

If you can find a mercury or attwood spin on filter to fit you can certainly run premix thru it without a problem. Good luck

Re: In hull gas tank...how to get fuel/oil mix into engine

Thanks Jimmbo and Will for your help. Ok so I can put fuel/oil in the tank under the hull without problem? And I have been looking for a fuel filter that won't have issues with oil but havent found anything, any suggestions to where I look, either online or at a marine store?

Re: In hull gas tank...how to get fuel/oil mix into engine

You can get an Attwood filter mount and spin on filter combo at WalMart for about $25, or if your current filter is the same form factor then you can get just the filter element for about $6. There won't be any issue with your tank so don't worry about oil in there. The oil is gasoline soluble so it's not like it ends up just floating around. Pre-mixing in the tank is a very common thing so don't over think the repercussions too hard Just get yourself an Attwood filter and have at it. It helps to get a pre-mix measurer from pretty much anywhere that sells marine things that way you don't have to do any calculations you just fill it to the level for X gallons under the 50/1 measurement.

edit: re-read your post about putting an external oil tank in the fuel tank.. maybe it's just not written clearly but there is no more oil tank if you are pre-mixing. You just dump in the oil then fill with the appropriate amount of gas. Oil first helps make sure you get it good and mixed.

Re: In hull gas tank...how to get fuel/oil mix into engine

Oil first can ensure a very oil rich mix at first and almost no oil as the tank runs low. The oils are not self mixing. Best way is to premix it in containers of known size, then pour it into the built in tanks, not the fastest way but it ensures consistant mixing.

Re: In hull gas tank...how to get fuel/oil mix into engine

jimmbo said:

Oil first can ensure a very oil rich mix at first and almost no oil as the tank runs low. The oils are not self mixing. Best way is to premix it in containers of known size, then pour it into the built in tanks, not the fastest way but it ensures consistant mixing.

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I don't stay up at night worrying about it. Oil in first, gas rushes in and begins the mixing process, then the tank sloshes around on the way to the dock, then you get on the water and it gets mixed like crazy.

I don't know about your local body of water but on even a modest day at WOT my tank might as well be on one of those paint can shakers at home depot

Re: In hull gas tank...how to get fuel/oil mix into engine

I'm filling a 20 gallon in hull tank. Most of the time I fill up I rarely have a rough estimate of how much it will take. Yes, I have a fuel gauge but it isn't that accurate, especially on the trailer. I start pumping gas and listen to the fuel venting. When the tank is getting full you will hear the venting sound increase in pitch. That's where I stop, get out my measuring tool, and put in the right amount of oil for about 1/2 - 1 gallons MORE of fuel. Then pump the remaining 1/2 - 1 gallons of fuel behind the oil, and it is a perfect fill. I have an inline clear fuel filter on the transom and have never seen the fuel dark blue or light blue, and I check it quite often while out on the water.

Every boat is different, but listen for that sound next time you are filling up.

Re: In hull gas tank...how to get fuel/oil mix into engine

archcycle said:

edit: re-read your post about putting an external oil tank in the fuel tank.. maybe it's just not written clearly but there is no more oil tank if you are pre-mixing. You just dump in the oil then fill with the appropriate amount of g Oil first helps make sure you get it good and mixed.

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I only brought up the external oil tank because my neighbor has one that is connected to his engine which is a 96 evinrude, which feeds into the engine underneath where the normal evinrude fuel feed is on my 82 evinrude, making me come to realize that the newer engines only have that or they are oil injected.

Re: In hull gas tank...how to get fuel/oil mix into engine

Thanks for the help guys, I installed a new fuel filter/ water separator. Now I can't get the gas mix from the tank to the engine. All it is the hose with the primer bulb from the fitting in the splashwell to the engine but it doesnt seem to be pulling the fuel from the tank.

Note: the tank is 24 gallons and I only put about 2 gallons in it( reason being because it is an old tank and don't want to be paying around $400[someone on another thread I looked at mentioned this] to pump it out. Do not know if this is enough or I need something else to get the fuel to start flowing to the engine. Like an electric pump that pushes it up inside the tank system, I'm not sure, don't now much about fuel tanks, just a thought that came to me.

Re: In hull gas tank...how to get fuel/oil mix into engine

Might be that the pick-up is two gallons off the bottom of the tank. not unusual at all. Plus you have to pump the bulb a lot to get fuel from the tank . First time can be a PITA. Closer to the tank with the bulb would help if you can do that.

Re: In hull gas tank...how to get fuel/oil mix into engine

Probably need a few more gallons than that for the pickup to work. Also make sure the tank vent is open or clear then point the primer bulb arrows upward and start squeezing, may take a little bit for it to pick up. Good luck