Two motors off one tank

[jfkkesler]

I recently traded my 4 stroke kicker for a 2 stroke so i could run my kicker and main motor off of the same gas tank. Now I am looking into how to go about doing that. I imagine that some kind of "T" would need to be put in the line, but I didn't see anything like that in the iBoats store. Anybody had any luck with this?

 

[tmcalavy]

Re: Two motors off one tank

Just retrofitted my early 60's aluminum runabout with a 9-gallon tank to feed two late 50's OMC Big Twin 35 hp outboards. Some wiser mariners told me to plumb the line with bulb from the tank to a brass T, then plumb a line with bulb to each motor from the tee. Haven't tried it yet, but hope to do so in a week or so...finishing up the cosmetics on one of the 35's. If no probs occur, I'll try to post a pix of the set-up then. I may have made the hoses too long. Trial and error will tell.

 

[Chris1956]

Re: Two motors off one tank

TM has described the correct fuel system set up.

Hey TM, why only 9 gallons for two motors? I would think 12-18 gal is minimum, as those motors can use up to 7 Gal/hour, at WOT.

 

[JoLin]

Re: Two motors off one tank

Fuel filter adapter kit w/spin-on filter- the one I bought at West Marine (I think it's a Sierra) for my old boat w/kicker had a manifold with 2 inlets and 2 outlets. I plugged one inlet. Ran hose from tank to the other inlet, then a hose with bulb from each outlet to each motor. Worked fine- set me back about $60 as I recall.

 

[Mark42]

Re: Two motors off one tank

The proper setup is to use a 3 way valve (on motor 1 -off- on motor 2). That will prevent any siphoning of fuel or air from the other line that can happen with a T fitting. Also, the primer bulb can be installed between the tank and the valve, so only one primer bulb is needed.

 

[gss036]

Re: Two motors off one tank

I was wondering if you are pre-mixing you gas for both motors? I only run 4 stroke engines and run both from one tank. I just take fuel from both sides of the Racor filter.

 

[jfkkesler]

Re: Two motors off one tank

Mark -- That's what i was worrying about, siphoning. But in that set-up, only one motor would be able to run at a time, correct? I do have the fuel filter/Water separator with dual inlets and outlets though, how would I go about hooking that up? Would there be a primer bulb on both of the outlets to the motor? And would siphoning come into play there? Thanks for all your great answers so far!

 

[jfkkesler]

Re: Two motors off one tank

gss- yes, I am pre mixing. I find that the ratio is the same for both motors, as they both run quite smoothly at about 50:1. Sometimes Ill go a little lower, 40:1 to help with some of the smoke.

 

[rs2k]

Re: Two motors off one tank

Do you mean 60:1?

40:1 means more oil and less gasoline.

Chaning oil ratio can be bad. You might want to consider changing to a synthetic if you want to get rid of the smoke. They make synthetics that can go to 100:1.

 

[tmcalavy]

Re: Two motors off one tank

Nine gallons is the primary tank, have an extra 6-gallon tank on board, too. Want to try the T with the twins, may move to the set-up JoLin described though. But if the T works, I'm golden for a while. I don't run the Big Twins WOT so they're not too thirsty.

 

[jfkkesler]

Re: Two motors off one tank

60:1 is what I meant. I always get that backwards. Do Synthetic oils get rid of smoke? I have never used one, maybe I should try it. I also read that once you switch to synthetic oil, you can't go back to conventional without risking engine damage. Is that true? Where would I find this synthetic oil for 2 strokes? All i have found by the way of synthetics is for 4 strokes.

 

[rs2k]

Re: Two motors off one tank

I have had great success with synthetic two stroke oil. Synthetic oil will in some cases completely get rid of smoke (Except for starting). That was the case with my air cooled 60 horse two-stroke engine. Synthetic oil also stops a lot of the carbon build up caused by petroleum oil.

Synthetic oil provides much better lubrication as long as you don't overheat your engine. I understand that petroleum oil will provide better protection in the seconds before the engine seizes do to overheating.

You should NEVER mix synthetic and petroleum oil. Make sure you drain or use up the rest of your gasoline before changing oils. I would also recommend changing your fuel filter and gas line.

As far as going from on oil to another, I don't think it's any problem as long as you don't let the two oils mix. On the first time running it I would just make sure to run the engine up to temperature to make sure all the old in the crank gets burned.

The two big drawbacks to synthetic oil is that it costs more and can be so slippery that the oil doesn't keep the engine parts coated after long periods of no use. There are synthetic oils that get around the lack of use problem. Amsoil makes a very good oil that still keeps the parts coated after running.

I would personally run AMSOIL Saber two stroke Outboard oil at 75:1 or 80:1. It says you can go to 100:1 but I've never been comfortable with that. It start to get easy to under mix that oil when you start to go that high. You might accidentally make the ratio 120:1 for example.

 

[Mark42]

Re: Two motors off one tank

Mark -- That's what i was worrying about, siphoning. But in that set-up, only one motor would be able to run at a time, correct? I do have the fuel filter/Water separator with dual inlets and outlets though, how would I go about hooking that up? Would there be a primer bulb on both of the outlets to the motor? And would siphoning come into play there? Thanks for all your great answers so far!

Run the line from the fuel tank to the filter, then from the filter to the primer bulb, then to the 3 way valve, then one line to each O/B.

And you are right, only one motor can run at a time.

A T fitting, especially a plastic one, is not the safest or best way to feed two motors from one tank.

 

[tmcalavy]

Re: Two motors off one tank

No plastic in my setup, only brass.

 

[ondarvr]

Re: Two motors off one tank

I use the fuel/water (filter) as the tee and you need a bulb in each line between the filter and motor, this way both can be run at the same time and there's no opening or closing anything, just start the one (or both) you want to use.

Synthetics are better at high temps than standard oils, not worse. The two can also be mixed in the system without damage, but its recommended that you run the tank low before changing types. You can switch back and forth as much as you want without problems.